Astronomy (from the Greek words astro(αστέρι) = star and nomos(νόμος) = law) is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation). The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into The Crab Nebula (catalogue designations M 1 NGC 1952 Taurus A is a Supernova remnant and Pulsar wind nebula in the Constellation A supernova remnant ( SNR) is the structure resulting from the gigantic explosion of a Star in a Supernova. Science (from the Latin scientia, meaning " Knowledge " or "knowing" is the effort to discover, and increase human understanding s are significant physical entities, associations or structures which current Science has confirmed to exist in Space. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter A phenomenon (from Greek φαινόμενoν, pl φαινόμενα - phenomena) is any observable occurrence Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Meteorology (from Greek grc μετέωρος metéōros, "high in the sky" and grc -λογία -logia) is the Interdisciplinary In Physics, motion means a constant change in the location of a body Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its
Astronomy is one of the oldest sciences. Astronomers of early civilizations performed methodical observations of the night sky, and astronomical artifacts have been found from much earlier periods. However, the invention of the telescope was required before astronomy was able to develop into a modern science. A telescope is an instrument designed for the observation of remote objects and the collection of Electromagnetic radiation. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, the making of calendars, and even astrology, but professional astronomy is nowadays often considered to be synonymous with astrophysics. Astrometry is the branch of Astronomy that relates to precise measurements and explanations of the positions and movements of Stars and other celestial bodies Celestial navigation, also known as astronavigation, is a Position fixing technique that was devised to help sailors cross the featureless oceans without having to The word Calendar consist of two words 1 Cal ( in Pashto means Year in Hindi and Persian is Sal- also means Year Astrology (from Greek grc ἄστρον astron, "constellation star" and grc -λογία -logia) is a group of Systems Astrophysics is the branch of Astronomy that deals with the Physics of the Universe, including the physical properties ( Luminosity, Since the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is a division of the astronomical Science that is concerned with getting data in contrast with Theoretical astrophysics which is Observational astronomy is focused on acquiring and analyzing data, mainly using basic principles of physics. Theoretical astronomy is oriented towards the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the observational results, and observations being used to confirm theoretical results.
Amateur astronomers have contributed to many important astronomical discoveries, and astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and observation of transient phenomena. Amateur astronomy, a subset of Astronomy, is a Hobby whose participants enjoy studying and observing celestial objects A phenomenon (from Greek φαινόμενoν, pl φαινόμενα - phenomena) is any observable occurrence
Old or even ancient astronomy is not to be confused with astrology, the belief system which claims that human affairs are correlated with the positions of celestial objects. Astrology (from Greek grc ἄστρον astron, "constellation star" and grc -λογία -logia) is a group of Systems Although the two fields share a common origin and a part of their methods (namely, the use of ephemerides), they are distinct. Astrology and astronomy are historically one and the same discipline ( Latin: astrologia) and were only gradually recognized as separate in western An ephemeris (plural ephemerides; from the Greek word ἐφήμερος ephemeros "daily" is a table of values that gives the positions of [1]
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Lexicology
The word astronomy literally means "law of the stars" (or "culture of the stars" depending on the translation) and is derived from the Greek αστρονομία, astronomia, from the words άστρον (astron, "star") and νόμος (nomos, "laws or cultures"). Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly
Use of terms "astronomy" and "astrophysics"
Generally, either the term "astronomy" or "astrophysics" may be used to refer to this subject. [2][3][4] Based on strict dictionary definitions, "astronomy" refers to "the study of objects and matter outside the earth's atmosphere and of their physical and chemical properties"[5] and "astrophysics" refers to the branch of astronomy dealing with "the behavior, physical properties, and dynamic processes of celestial objects and phenomena". [6] In some cases, as in the introduction of the introductory textbook The Physical Universe by Frank Shu, "astronomy" may be used to describe the qualitative study of the subject, whereas "astrophysics" is used to describe the physics-oriented version of the subject. Frank Shu (born in Kunming, China) is an Astrophysicist, Author and Professor of Astronomy at the University [7] However, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics. [2] Various departments that research this subject may use "astronomy" and "astrophysics", partly depending on whether the department is historically affiliated with a physics department,[3] and many professional astronomers actually have physics degrees. [4] Even the name of the scientific journal Astronomy & Astrophysics reveals the ambiguity of the use of the term. Astronomy and Astrophysics (abbreviated as A&A in the astronomical literature or else Astron
History
- Further information: Archaeoastronomy
In early times, astronomy only comprised the observation and predictions of the motions of objects visible to the naked eye. In some locations, such as Stonehenge, early cultures assembled massive artifacts that likely had some astronomical purpose. Stonehenge is a Prehistoric Monument located in the English county of Wiltshire, about west of Amesbury and north of Salisbury In addition to their ceremonial uses, these observatories could be employed to determine the seasons, an important factor in knowing when to plant crops, as well as in understanding the length of the year. [8]
Before tools such as the telescope were invented early study of the stars had to be conducted from the only vantage points available, namely tall buildings, trees and high ground using the bare eye.
As civilizations developed, most notably in Mesopotamia, Greece, Egypt, Persia, Maya, India, China, and the Islamic world, astronomical observatories were assembled, and ideas on the nature of the universe began to be explored. Babylonian astronomy refers to the astronomical theories and methods that were developed in ancient Mesopotamia, the "land between the rivers" Tigris Greek astronomy is the Astronomy of those who wrote in the Greek language in Classical antiquity. Ancient Egypt was an Ancient Civilization in eastern North Africa, concentrated along the lower reaches of the Nile River in what is now The Persian Empire was a series of Iranian empires that ruled over the Iranian plateau, the original Persian homeland and beyond in Western Asia The Maya civilization is a Mesoamerican Civilization, noted for the only known fully developed written language of the Pre-Columbian Americas Indian astronomy —the earliest textual mention of which is given in the religious literature of India (2nd millennium BCE—became an established tradition by the 1st millennium BCE Astronomy in China has a very long history Oracle bones from the Shang Dynasty ( 2nd millennium BC) record eclipses and novae Most of early astronomy actually consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. Astrometry is the branch of Astronomy that relates to precise measurements and explanations of the positions and movements of Stars and other celestial bodies From these observations, early ideas about the motions of the planets were formed, and the nature of the Sun, Moon and the Earth in the universe were explored philosophically. The Earth was believed to be the center of the universe with the Sun, the Moon and the stars rotating around it. This is known as the geocentric model of the universe.
A few notable astronomical discoveries were made prior to the application of the telescope. For example, the obliquity of the ecliptic was estimated as early as 1000 BC by the Chinese. In Astronomy, axial tilt is the Inclination angle of a planet's rotational axis in relation to its orbital plane. The Chaldeans discovered that lunar eclipses recurred in a repeating cycle known as a saros. Babylonian astronomy refers to the astronomical theories and methods that were developed in ancient Mesopotamia, the "land between the rivers" Tigris A lunar eclipse occurs whenever the Moon passes through some portion of the Earth's shadow The Saros cycle is an Eclipse cycle with a period of about 18 years 11 days 8 hours (approximately 6585⅓ days that can be used to predict Eclipses of the Sun [9] In the 2nd century BC, the size and distance of the Moon were estimated by Hipparchus. Hipparchus ( Greek; ca 190 BC &ndash ca 120 BC was a Greek Astronomer, Geographer, and Mathematician of the Hellenistic [10]
During the Middle Ages, observational astronomy was mostly stagnant in medieval Europe, at least until the 13th century. However, observational astronomy flourished in the Islamic world and other parts of the world. Some of the prominent Arab astronomers, who made significant contributions to the science were Al-Battani and Thebit. (836 in Harran, Mesopotamia &ndash February 18, 901 in Baghdad) was an Arab astronomer, mathematician Astronomers during that time introduced many Arabic names that are now used for individual stars. Arabic (ar الْعَرَبيّة (informally ar عَرَبيْ) in terms of the number of speakers is the largest living member of the Semitic language [11][12]
Scientific revolution
During the Renaissance, Nicolaus Copernicus proposed a heliocentric model of the solar system. The Renaissance (from French Renaissance, meaning "rebirth" Italian: Rinascimento, from re- "again" and nascere In Astronomy, heliocentrism is the theory that the Sun is at the center of the Solar System. The Solar System consists of the Sun and those celestial objects bound to it by Gravity. His work was defended, expanded upon, and corrected by Galileo Galilei and Johannes Kepler. Galileo Galilei (15 February 1564 &ndash 8 January 1642 was a Tuscan ( Italian) Physicist, Mathematician, Astronomer, and Philosopher Johannes Kepler (ˈkɛplɚ ( December 27 1571 &ndash November 15 1630) was a German Mathematician, Astronomer Galileo innovated by using telescopes to enhance his observations.
Kepler was the first to devise a system that described correctly the details of the motion of the planets with the Sun at the center. However, Kepler did not succeed in formulating a theory behind the laws he wrote down. It was left to Newton's invention of celestial dynamics and his law of gravitation to finally explain the motions of the planets. Sir Isaac Newton, FRS (ˈnjuːtən 4 January 1643 31 March 1727) Biography Early years See also Isaac Newton's early life and achievements Celestial mechanics is the branch of Astrophysics that deals with the motions of Celestial objects The field applies principles of Physics, historically Gravitation is a natural Phenomenon by which objects with Mass attract one another Newton also developed the reflecting telescope. A reflecting telescope (also called a reflector) is an Optical telescope which uses a single or combination of Curved mirrors that reflect Light
Further discoveries paralleled the improvements in the size and quality of the telescope. More extensive star catalogues were produced by Lacaille. Abbé Nicolas Louis de Lacaille ( March 15, 1713 &ndash March 21, 1762) was a French Astronomer. The astronomer William Herschel made a detailed catalog of nebulosity and clusters, and in 1781 discovered the planet Uranus, the first new planet found. Sir Frederick William Herschel FRS KH ( 15 November 1738 – 25 August 1822) was a German -born British The distance to a star was first announced in 1838 when the parallax of 61 Cygni was measured by Friedrich Bessel. Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between Not be confused with 16 Cygni, a more distant system containing two G-type stars harboring the Gas giant planet 16 Cygni Bb. Friedrich Wilhelm Bessel (22 July 1784 &ndash 17 March 1846 was a German Mathematician, Astronomer, and systematizer of the Bessel functions
During the nineteenth century, attention to the three body problem by Euler, Clairaut, and D'Alembert led to more accurate predictions about the motions of the Moon and planets. The n -body problem is the problem of finding given the initial positions masses and velocities of n bodies their subsequent motions as determined by Alexis Claude de Clairault (or Clairaut) ( May 3, 1713 – May 17, 1765) was a French Mathematician and This work was further refined by Lagrange and Laplace, allowing the masses of the planets and moons to be estimated from their perturbations.
Significant advances in astronomy came about with the introduction of new technology, including the spectroscope and photography. A spectrometer is an Optical instrument used to measure properties of Light over a specific portion of the Electromagnetic spectrum, typically used Photography (fә'tɒgrәfi or fә'tɑːgrәfi (from Greek φωτο and γραφία is the process and Art of recording pictures by means of capturing Fraunhofer discovered about 600 bands in the spectrum of the Sun in 1814-15, which, in 1859, Kirchhoff ascribed to the presence of different elements. Joseph von Fraunhofer ( March 6, 1787 &ndash June 7, 1826) was a German optician Gustav Robert Kirchhoff ( March 12, 1824 &ndash October 17, 1887) was a German Physicist who contributed to the fundamental Stars were proven to be similar to the Earth's own Sun, but with a wide range of temperatures, masses, and sizes. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object [11]
The existence of the Earth's galaxy, the Milky Way, as a separate group of stars, was only proved in the 20th century, along with the existence of "external" galaxies, and soon after, the expansion of the universe, seen in the recession of most galaxies from us. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy Modern astronomy has also discovered many exotic objects such as quasars, pulsars, blazars, and radio galaxies, and has used these observations to develop physical theories which describe some of these objects in terms of equally exotic objects such as black holes and neutron stars. A quasar (contraction of QUASi-stellAR radio source) is an extremely powerful and distant Active galactic nucleus. Pulsars are highly magnetized rotating Neutron stars that emit a beam of Electromagnetic radiation in the form of radio waves A blazar is a very compact and highly variable energy source associated with a presumed Supermassive black hole at the center of a Host galaxy. Radio galaxies and their relatives radio-loud Quasars and Blazars, are types of Active galaxy that are very luminous at radio wavelengths (up A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type Physical cosmology made huge advances during the 20th century, with the model of the Big Bang heavily supported by the evidence provided by astronomy and physics, such as the cosmic microwave background radiation, Hubble's law, and cosmological abundances of elements. Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. Hubble's law is the statement in Physical cosmology that the Redshift in light coming from distant galaxies is proportional to their distance In Physical cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than those of H-1 (i
Observational astronomy
In astronomy, information is mainly received from the detection and analysis of visible light or other regions of the electromagnetic radiation. Observational astronomy is a division of the astronomical Science that is concerned with getting data in contrast with Theoretical astrophysics which is Information as a concept has a diversity of meanings from everyday usage to technical settings Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. [13] Observational astronomy may be divided according to the observed region of the electromagnetic spectrum. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies Some parts of the spectrum can be observed from the Earth's surface, while other parts are only observable from either high altitudes or space. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Specific information on these subfields is given below.
Radio astronomy
Radio astronomy studies radiation with wavelengths greater than approximately one millimeter. Radio astronomy is a subfield of Astronomy that studies celestial objects at radio frequencies. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to [14] Radio astronomy is different from most other forms of observational astronomy in that the observed radio waves can be treated as waves rather than as discrete photons. Radio waves are electromagnetic waves occurring on the Radio frequency portion of the Electromagnetic spectrum. A wave is a disturbance that propagates through Space and Time, usually with transference of Energy. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Hence, it is relatively easier to measure both the amplitude and phase of radio waves, whereas this is not as easily done at shorter wavelengths. Amplitude is the magnitude of change in the oscillating variable with each Oscillation, within an oscillating system The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0 [14]
Though some radio waves are produced by astronomical objects in the form of thermal emission, most of the radio emission that is observed from Earth is seen in the form of synchrotron radiation, which is produced when electrons oscillate around magnetic fields. Radio waves are electromagnetic waves occurring on the Radio frequency portion of the Electromagnetic spectrum. The Electromagnetic radiation emitted by a Black body. You may also be looking for Incandescence, the radiation from a body This article concerns the physical phenomenon of synchrotron radiation The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges [14] Additionally, a number of spectral lines produced by interstellar gas, notably the hydrogen spectral line at 21 cm, are observable at radio wavelengths. A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 A centimetre ( American spelling: centimeter, symbol cm) is a unit of Length in the Metric system, equal to one hundredth [7][14]
A wide variety of objects are observable at radio wavelengths, including supernovae, interstellar gas, pulsars, and active galactic nuclei. A supernova (plural supernovae or supernovas) is a stellar Explosion. Pulsars are highly magnetized rotating Neutron stars that emit a beam of Electromagnetic radiation in the form of radio waves An active galactic nucleus ( AGN) is a compact region at the centre of a Galaxy which has a much higher than normal luminosity over some or all of the Electromagnetic [7][14]
Infrared astronomy
Infrared astronomy deals with the detection and analysis of infrared radiation (wavelengths longer than red light). Infrared astronomy is the branch of Astronomy and Astrophysics which deals with objects visible in Infrared (IR radiation Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Except at wavelengths close to visible light, infrared radiation is heavily absorbed by the atmosphere, and the atmosphere produces significant infrared emission. Consequently, infrared observatories have to be located in high, dry places or in space. Infrared astronomy is particularly useful for observation of galactic regions cloaked by dust, and for studies of molecular gases.
Optical astronomy
Historically, optical astronomy, also called visible light astronomy, is the oldest form of astronomy. [15] Optical images were originally drawn by hand. In the late nineteenth century and most of the twentieth century, images were made using photographic equipment. Modern images are made using digital detectors, particularly detectors using charge-coupled devices (CCDs). A charge-coupled device ( CCD) is an analog Shift register, that enables the transportation of analog signals (electric charges through successive stages (capacitors Although visible light itself extends from approximately 4000 Å to 7000 Å (400 nm to 700 nm),[15] the same equipment used at these wavelengths is also used to observe some near-ultraviolet and near-infrared radiation. An ångström or angstrom (symbol Å) (ˈɔːŋstrəm Swedish: ˈɔ̀ŋstrœm is an internationally recognized non- SI unit of length equal A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of
Ultraviolet astronomy
Ultraviolet astronomy is generally used to refer to observations at ultraviolet wavelengths between approximately 100 and 3200 Å (10 to 320 nm). Ultraviolet astronomy is generally used to refer to observations at Ultraviolet wavelengths between approximately 10 and 320 nanometres Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays [14] Light at these wavelengths is absorbed by the Earth's atmosphere, so observations at these wavelengths must be performed from the upper atmosphere or from space. Ultraviolet astronomy is best suited to the study of thermal radiation and spectral emission lines from hot blue stars (OB stars) that are very bright in this wave band. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth OB stars are hot massive Stars of spectral types O or B which form in loosely organized groups called OB associations They are short lived and This includes the blue stars in other galaxies, which have been the targets of several ultraviolet surveys. Other objects commonly observed in ultraviolet light include planetary nebulae, supernova remnants, and active galactic nuclei. A planetary nebula is an Emission nebula consisting of a glowing shell of Gas and plasma formed by certain types of Stars when they die A supernova remnant ( SNR) is the structure resulting from the gigantic explosion of a Star in a Supernova. [14] However, ultraviolet light is easily absorbed by interstellar dust, and measurement of the ultraviolet light from objects need to be corrected for extinction. [14]
X-ray astronomy
X-ray astronomy is the study of astronomical objects at X-ray wavelengths. X-ray astronomy is an observational branch of Astronomy, which deals with the study of X-ray emission from celestial objects Typically, objects emit X-ray radiation as synchrotron emission (produced by electrons oscillating around magnetic field lines), thermal emission from thin gases (called bremsstrahlung radiation) that is above 107 (10 million) kelvins, and thermal emission from thick gases (called blackbody radiation) that are above 107 Kelvin. This article concerns the physical phenomenon of synchrotron radiation Bremsstrahlung ( pronounced, from German de ''bremsen'' "to brake" and de ''Strahlung'' "radiation" i The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic The Electromagnetic radiation emitted by a Black body. You may also be looking for Incandescence, the radiation from a body [14] Since X-rays are absorbed by the Earth's atmosphere, all X-ray observations must be done from high-altitude balloons, rockets, or spacecraft. A rocket or rocket vehicle is a Missile, Aircraft or other Vehicle which obtains Thrust by the reaction of the Notable X-ray sources include X-ray binaries, pulsars, supernova remnants, elliptical galaxies, clusters of galaxies, and active galactic nuclei. X-ray binaries are a class of Binary stars that are luminous in X-rays The X-rays are produced by matter falling from one component (usually a relatively normal Pulsars are highly magnetized rotating Neutron stars that emit a beam of Electromagnetic radiation in the form of radio waves An elliptical galaxy is a Galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble (whose name was dedicated Galaxy groups and clusters are the largest Gravitationally bound objects to have arisen thus far in the process of cosmic structure formation [14]
Gamma-ray astronomy
Gamma ray astronomy is the study of astronomical objects at the shortest wavelengths of the electromagnetic spectrum. Gamma-ray astronomy is the astronomical study of the Cosmos with Gamma rays. Gamma rays may be observed directly by satellites such as the Compton Gamma Ray Observatory or by specialized telescopes called atmospheric Cherenkov telescopes. The IACT or Imaging Atmospheric Cherenkov Technique is the method whereby very high energy Gamma-ray Photons in the 50 GeV to 50 TeV [14] The Cherenkov telescopes do not actually detect the gamma rays directly but instead detect the flashes of visible light produced when gamma rays are absorbed by the Earth's atmosphere. [16]
Most gamma-ray emitting sources are actually gamma-ray bursts, objects which only produce gamma radiation for a few milliseconds to thousands of seconds before fading away. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions Gamma-ray bursts ( GRB s are the most luminous electromagnetic events occurring in the Universe since the Big Bang. Only 10% of gamma-ray sources are non-transient sources. These steady gamma-ray emitters include pulsars, neutron stars, and black hole candidates such as active galactic nuclei. A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e [14]
Fields of observational astronomy not based on the electromagnetic spectrum
Other than electromagnetic radiation, few things may be observed from the Earth that originate from great distances.
In neutrino astronomy, astronomers use special underground facilities such as SAGE, GALLEX, and Kamioka II/III for detecting neutrinos. Neutrino astronomy is the branch of astronomy that observes astronomical objects with neutrino detectors in special observatories GALLEX or Gallium Experiment was a radiochemical Neutrino detection experiment that ran between 1991 and 1997 at the Laboratori Nazionali del Gran Sasso Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost These neutrinos originate primarily from the Sun but also from supernovae. The Sun (Sol is the Star at the center of the Solar System. A supernova (plural supernovae or supernovas) is a stellar Explosion. [14]
Cosmic rays consisting of very high energy particles can be observed hitting the Earth's atmosphere. For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on Additionally, some future neutrino detectors will also be sensitive to the neutrinos produced when cosmic rays hit the Earth's atmosphere. [14]
A few gravitational wave observatories have been constructed, such as the Laser Interferometer Gravitational Observatory (LIGO) but gravitational waves are extremely difficult to detect. In Physics, a gravitational wave is a Fluctuation in the Curvature of Spacetime which propagates as a wave, traveling outward from [17]
Planetary astronomy has benefited from direct observation in the form of spacecraft and sample return missions. These include fly-by missions with remote sensors; landing vehicles that can perform experiments on the surface materials; impactors that allow remote sensing of buried material, and sample return missions that allow direct, laboratory examination.
Astrometry and celestial mechanics
One of the oldest fields in astronomy, and in all of science, is the measurement of the positions of celestial objects. Astrometry is the branch of Astronomy that relates to precise measurements and explanations of the positions and movements of Stars and other celestial bodies Celestial mechanics is the branch of Astrophysics that deals with the motions of Celestial objects The field applies principles of Physics, historically Historically, accurate knowledge of the positions of the Sun, Moon, planets and stars has been essential in celestial navigation. Celestial navigation, also known as astronavigation, is a Position fixing technique that was devised to help sailors cross the featureless oceans without having to
Careful measurement of the positions of the planets has led to a solid understanding of gravitational perturbations, and an ability to determine past and future positions of the planets with great accuracy, a field known as celestial mechanics. This article describes perturbation theory as a general mathematical method Celestial mechanics is the branch of Astrophysics that deals with the motions of Celestial objects The field applies principles of Physics, historically More recently the tracking of near-Earth objects will allow for predictions of close encounters, and potential collisions, with the Earth. Near-Earth objects ( NEOs) are Asteroids Comets and large Meteoroids whose orbits bring them close ( Perihelion distance AU [18]
The measurement of stellar parallax of nearby stars provides a fundamental baseline in the cosmic distance ladder that is used to measure the scale of the universe. Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between The cosmic distance ladder (also known as the Extragalactic Distance Scale) is the succession of methods by which astronomers determine the Distances to celestial Parallax measurements of nearby stars provide an absolute baseline for the properties of more distant stars, because their properties can be compared. Measurements of radial velocity and proper motion show the kinematics of these systems through the Milky Way galaxy. Radial velocity is the Velocity of an object in the direction of the line of sight (i The proper motion of a Star is the measurement of its change in position in the sky over time after Improper motions are accounted for Astrometric results are also used to measure the distribution of dark matter in the galaxy. In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from [19]
During the 1990s, the astrometric technique of measuring the stellar wobble was used to detect large extrasolar planets orbiting nearby stars. Stellar wobble is a variation in the position of a Star due to the gravitational influence of another body orbiting it Any Planet is an extremely faint light source compared to its parent Star. An extrasolar planet, or exoplanet, is a Planet beyond the Solar System, orbiting around other Stars As of September 2008 312 [20]
Theoretical astronomy
Theoretical astronomers use a wide variety of tools which include analytical models(for example, polytropesto approximate the behaviors of a star) and computationalnumerical simulations. Note The term model has a different meaning in Model theory, a branch of Mathematical logic. In Astrophysics, a polytrope refers to a solution of the Lane-Emden equation in which the Pressure depends upon the Density in the form P A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth Computation is a general term for any type of Information processing. Numerical analysis is the study of Algorithms for the problems of continuous mathematics (as distinguished from Discrete mathematics) Each has some advantages. Analytical models of a process are generally better for giving insight into the heart of what is going on. Numerical models can reveal the existence of phenomena and effects that would otherwise not be seen. [21][22]Theorists in astronomy endeavor to create theoretical models and figure out the observational consequences of those models. This helps observers look for data that can refute a model or help in choosing between several alternate or conflicting models. Theorists also try to generate or modify models to take into account new data. In the case of an inconsistency, the general tendency is to try to make minimal modifications to the model to fit the data. In some cases, a large amount of inconsistent data over time may lead to total abandonment of a model. Topics studied by theoretical astronomers include: stellar dynamicsand evolution; galaxy formation; large-scale structureof matterin the Universe; origin of cosmic rays; general relativityand physical cosmology, including stringcosmology and astroparticle physics. Stellar dynamics is the branch of Astrophysics which describes in a statistical way the collective motions of Stars subject to their mutual Gravity. Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning the formation of the first galaxies the way In Physical cosmology, the term large-scale structure refers to the characterization of observable distributions of Matter and Light Matter is commonly defined as being anything that has mass and that takes up space. The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its String theory is a still-developing scientific approach to Theoretical physics, whose original building blocks are one-dimensional extended objects called strings Astroparticle physics is a term used to indicate that branch of Particle physics that studies elementary particles of astronomical origin and their relation to Astrophysics Astrophysical relativity serves as a tool to gauge the properties of large scale structures for which gravitation plays a significant role in physical phenomena investigated and as the basis for black hole(astro)physicsand the study of gravitational waves. A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. In Physics, a gravitational wave is a Fluctuation in the Curvature of Spacetime which propagates as a wave, traveling outward from Some widely accepted and studied theories and models in astronomy, now included in the Lambda-CDM modelare the Big Bang, Cosmic inflation, dark matter, and fundamental theories of physics. &LambdaCDM or Lambda-CDM is an abbreviation for Lambda-Cold Dark Matter. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. In Physical cosmology, cosmic inflation is the idea that the nascent Universe passed through a phase of exponential expansion that In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. A few examples of this process:
| Nucleosynthesis | |||
| Physical process | Experimental tool | Theoretical model | Explains/predicts |
| Gravitation | Radio telescopes | Self-gravitating system | Emergence of a star system |
| Nuclear fusion | Spectroscopy | Stellar evolution | How the stars shine and how metals formed |
| The Big Bang | Hubble Space Telescope, COBE | Expanding universe | Age of the Universe |
| Quantum fluctuations | Cosmic inflation | Flatness problem | |
| Gravitational collapse | X-ray astronomy | General relativity | Black holes at the center of Andromeda galaxy |
| CNO cycle in stars |
Dark matter and dark energy are the current leading topics in astronomy, as their discovery and controversy originated during the study of the galaxies. Nucleosynthesis is the process of creating new atomic nuclei from preexisting Nucleons (protons and neutrons Gravitation is a natural Phenomenon by which objects with Mass attract one another A radio telescope is a form of directional Radio antenna used in Radio astronomy and in tracking and collecting data from Satellites In Theoretical astrophysics, the Nordtvedt effect refers to the relative motion between the Earth and the Moon which would be observed if the A star system or stellar system is a small number of Stars which orbit each other bound by gravitational attraction. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime Nucleosynthesis is the process of creating new atomic nuclei from preexisting Nucleons (protons and neutrons The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into The metric expansion of space is the averaged increase of metric (i The age of the Universe is the time elapsed between the theory of the Big Bang and the present day In Quantum physics, a quantum fluctuation is the temporary change in the amount of energy in a point in space arising from Werner Heisenberg 's Uncertainty principle In Physical cosmology, cosmic inflation is the idea that the nascent Universe passed through a phase of exponential expansion that The flatness problem is a cosmological Fine-tuning problem within the Big Bang model i Gravitational collapse in Astronomy is the inward fall of a massive body under the influence of the force of Gravity. X-ray astronomy is an observational branch of Astronomy, which deals with the study of X-ray emission from celestial objects General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e The Andromeda Galaxy (ænˈdrɒmədə also known as Messier 31, M31, or NGC 224; often referred to as the Great Andromeda The CNO cycle (for Carbon - Nitrogen - Oxygen) or sometimes Bethe-Weizsäcker-cycle, is one of two sets of fusion reactions A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from In Physical cosmology, dark energy is a hypothetical exotic form of Energy that permeates all of space and tends to increase the rate of expansion of the universe
Subfield of astronomy for specific astronomical objects
Solar astronomy
At a distance of about eight light-minutes, the most frequently studied star is the Sun, a typical main-sequence dwarf star of stellar class G2 V, and about 4. The Sun (Sol is the Star at the center of the Solar System. The Sun (Sol is the Star at the center of the Solar System. The term dwarf star refers to a variety of distinct classes of Stars Dwarf star alone generally refers to any Main sequence star a star In Astronomy, stellar classification is a classification of Stars based initially on photospheric temperature and its associated Spectral characteristics 6 Gyr in age. The Sun is not considered a variable star, but it does undergo periodic changes in activity known as the sunspot cycle. For the astronomical object see Variable star. Variable Star is a 2006 novel written by Spider Robinson This is an 11-year fluctuation in sunspot numbers. A sunspot is a region on the Sun 's surface ( Photosphere) that is marked by intense magnetic activity which inhibits Convection, forming Sunspots are regions of lower-than- average temperatures that are associated with intense magnetic activity. [23]
The Sun has steadily increased in luminosity over the course of its life, increasing by 40% since it first became a main-sequence star. The Sun has also undergone periodic changes in luminosity that can have a significant impact on the Earth. [24] The Maunder minimum, for example, is believed to have caused the Little Ice Age phenomenon during the Middle Ages. The Maunder Minimum is the name given to the period roughly from 1645 to 1715, when Sunspots became exceedingly rare as noted by solar observers of The Little Ice Age (LIA was a period of cooling occurring after a warmer era known as the Medieval Warm Period or Medieval Climate Optimum [25]
The visible outer surface of the Sun is called the photosphere. Above this layer is a thin region known as the chromosphere. The chromosphere (literally "colour sphere" is a thin layer of the Sun 's atmosphere just above the Photosphere, roughly 10000 kilometres deep This is surrounded by a transition region of rapidly increasing temperatures, then by the super-heated corona. A corona is a type of plasma " atmosphere " of the Sun or other celestial body extending millions of Kilometres into space most easily
At the center of the Sun is the core region, a volume of sufficient temperature and pressure for nuclear fusion to occur. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus Above the core is the radiation zone, where the plasma conveys the energy flux by means of radiation. The radiation zone is the middle zone in the Sun 's interior Energy travels out of the core into the radiation zone The outer layers form a convection zone where the gas material transports energy primarily through physical displacement of the gas. The convection zone of a Star is the range of radii in which energy is transported primarily by Convection. It is believed that this convection zone creates the magnetic activity that generates sun spots. [23]
A solar wind of plasma particles constantly streams outward from the Sun until it reaches the heliopause. The heliosphere is a bubble in space "blown" into the Interstellar medium (the hydrogen and helium gas that permeates the Galaxy) by the This solar wind interacts with the magnetosphere of the Earth to create the Van Allen radiation belts, as well as the aurora where the lines of the Earth's magnetic field descend into the atmosphere. A magnetosphere' is a highly magnetized region around and possessed by an Astronomical object. The Van Allen radiation belt is a Torus of energetic Charged particles ( plasma) around Earth, held in place by Earth's Magnetic Earth 's magnetic field (and the surface magnetic field) is approximately a Magnetic dipole, with one pole near the North pole (see Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five [26]
Planetary science
This astronomical field examines the assemblage of planets, moons, dwarf planets, comets, asteroids, and other bodies orbiting the Sun, as well as extrasolar planets. Planetary science, also known as planetology and closely related to planetary astronomy, is the Science of Planets or Planetary systems Planetary geology, alternatively known as astrogeology or exogeology, is a Planetary science discipline concerned with the Geology of the A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is A natural satellite or moon is a Celestial body that Orbits a Planet or smaller body which is called the primary. A dwarf planet, as defined by the International Astronomical Union (IAU is a Celestial body Orbiting the Sun that is massive enough to be rounded A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — Asteroids, sometimes called Minor planets or planetoids', are bodies—primarily of the inner Solar System —that are smaller than planets but The solar system has been relatively well-studied, initially through telescopes and then later by spacecraft. The Solar System consists of the Sun and those celestial objects bound to it by Gravity. This has provided a good overall understanding of the formation and evolution of this planetary system, although many new discoveries are still being made. [27]
The solar system is subdivided into the inner planets, the asteroid belt, and the outer planets. The asteroid belt is the region of the Solar System located roughly between the orbits of the Planets Mars and Jupiter. The inner terrestrial planets consist of Mercury, Venus, Earth, and Mars. A terrestrial planet, telluric planet or rocky planet is a Planet that is primarily composed of Silicate rocks Within our The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The outer gas giant planets are Jupiter, Saturn, Uranus and Neptune. A gas giant (sometimes also known as a Jovian planet after the planet Jupiter, or giant planet) is a large Planet that is not primarily Neptune ( English|AmE] ] is the eighth and farthest Planet from the Sun in the Solar System. [28] Beyond Neptune lie the Kuiper Belt, and finally the Oort Cloud, which may extend as far as a light-year. The Kuiper belt (ˈkaɪpɚ to rhyme with "viper" sometimes called the Edgeworth-Kuiper belt, is a region of the Solar System beyond the planets extending The Oort cloud ( ort alternatively the Öpik-Oort Cloud) is a hypothetical spherical cloud of Comets believed to lie roughly 50 000 AU,
The planets were formed by a protoplanetary disk that surrounded the early Sun. A protoplanetary disk (or proplyd) is a rotating Circumstellar disk of dense gas surrounding a young newly formed star a T Tauri star or Herbig star Through a process that included gravitational attraction, collision, and accretion, the disk formed clumps of matter that, with time, became protoplanets. The radiation pressure of the solar wind then expelled most of the unaccreted matter, and only those planets with sufficient mass retained their gaseous atmosphere. Radiation pressure is the Pressure exerted upon any surface exposed to Electromagnetic radiation. The solar wind is a Stream of charged particles&mdasha plasma &mdashthat are ejected from the upper atmosphere of the Sun. The planets continued to sweep up, or eject, the remaining matter during a period of intense bombardment, evidenced by the many impact craters on the Moon. In the broadest sense the term impact crater can be applied to any depression natural or manmade resulting from the high velocity impact of a projectile with larger body During this period, some of the protoplanets may have collided, the leading hypothesis for how the Moon was formed. [29]
Once a planet reaches sufficient mass, the materials with different densities segregate within, during planetary differentiation. In Planetary science, planetary differentiation is the process of separating out different constituents of a planetary body as a consequence of their physical or chemical This process can form a stony or metallic core, surrounded by a mantle and an outer surface. The core may include solid and liquid regions, and some planetary cores generate their own magnetic field, which can protect their atmospheres from solar wind stripping. In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges [30]
A planet or moon's interior heat is produced from the collisions that created the body, radioactive materials (e. g. uranium, thorium, and 26Al), or tidal heating. Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Thorium (ˈθɔːriəm is a Chemical element with the symbol Th and Atomic number 90 WikipediaNaming Tidal acceleration is an effect of the Tidal forces between an orbiting Natural satellite ( i Some planets and moons accumulate enough heat to drive geologic processes such as volcanism and tectonics. Plate tectonics and hotspots Divergent plate boundaries At the Those that accumulate or retain an atmosphere can also undergo surface erosion from wind or water. An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind Smaller bodies, without tidal heating, cool more quickly; and their geological activity ceases with the exception of impact cratering. [31]
Stellar astronomy
The study of stars and stellar evolution is fundamental to our understanding of the universe. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime The astrophysics of stars has been determined through observation and theoretical understanding; and from computer simulations of the interior.
Star formation occurs in dense regions of dust and gas, known as giant molecular clouds. Star Formation is the process by which dense parts of Molecular clouds collapse into a ball of plasma to form a Star. A dark nebula is a type of Interstellar cloud that is so dense that it obscures the light from the background emission or Reflection nebula (e When destabilized, cloud fragments can collapse under the influence of gravity, to form a protostar. A protostar is a large object that forms by contraction out of the gas of a Giant molecular cloud in the Interstellar medium. A sufficiently dense, and hot, core region will trigger nuclear fusion, thus creating a main-sequence star. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness [32]
Almost all elements heavier than hydrogen and helium were created inside the cores of stars. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Nucleosynthesis is the process of creating new atomic nuclei from preexisting Nucleons (protons and neutrons
The characteristics of the resulting star depend primarily upon its starting mass. The more massive the star, the greater its luminosity, and the more rapidly it expends the hydrogen fuel in its core. Over time, this hydrogen fuel is completely converted into helium, and the star begins to evolve. Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime The fusion of helium requires a higher core temperature, so that the star both expands in size, and increases in core density. The resulting red giant enjoys a brief life span, before the helium fuel is in turn consumed. A red giant is a luminous Giant star of low or intermediate mass (roughly 0 Very massive stars can also undergo a series of decreasing evolutionary phases, as they fuse increasingly heavier elements.
The final fate of the star depends on its mass, with stars of mass greater than about eight times the Sun becoming core collapse supernovae; while smaller stars form planetary nebulae, and evolve into white dwarfs. The Sun (Sol is the Star at the center of the Solar System. A supernova (plural supernovae or supernovas) is a stellar Explosion. A planetary nebula is an Emission nebula consisting of a glowing shell of Gas and plasma formed by certain types of Stars when they die A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. The remnant of a supernova is a dense neutron star, or, if the stellar mass was at least three times that of the Sun, a black hole. A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e [33] Close binary stars can follow more complex evolutionary paths, such as mass transfer onto a white dwarf companion that can potentially cause a supernova. Planetary nebulae and supernovae are necessary for the distribution of metals to the interstellar medium; without them, all new stars (and their planetary systems) would be formed from hydrogen and helium alone. In Astronomy and Physical cosmology, the metallicity of an object is the proportion of its matter made up of Chemical elements other than Hydrogen
Galactic astronomy
Our solar system orbits within the Milky Way, a barred spiral galaxy that is a prominent member of the Local Group of galaxies. Galactic astronomy is the study of our own Milky Way galaxy and all its contents The Solar System consists of the Sun and those celestial objects bound to it by Gravity. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply A barred spiral galaxy is a Spiral galaxy with a central bar-shaped structure composed of Stars Bars are found in approximately half of all spiral galaxies The Local Group is the group of galaxies that includes our galaxy the Milky Way. It is a rotating mass of gas, dust, stars and other objects, held together by mutual gravitational attraction. As the Earth is located within the dusty outer arms, there are large portions of the Milky Way that are obscured from view.
In the center of the Milky Way is the core, a bar-shaped bulge with what is believed to be a supermassive black hole at the center. A supermassive black hole is a Black hole with a Mass of an order of magnitude between 105 and 1 This is surrounded by four primary arms that spiral from the core. This is a region of active star formation that contains many younger, population II stars. In Astronomy and Physical cosmology, the metallicity of an object is the proportion of its matter made up of Chemical elements other than Hydrogen The disk is surrounded by a spheroid halo of older, population I stars, as well as relatively dense concentrations of stars known as globular clusters. A spiral galaxy is a Galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the In Astronomy and Physical cosmology, the metallicity of an object is the proportion of its matter made up of Chemical elements other than Hydrogen A globular cluster is a spherical collection of Stars that orbits a galactic core as a Satellite. [34][35]
Between the stars lies the interstellar medium, a region of sparse matter. In the densest regions, molecular clouds of molecular hydrogen and other elements create star-forming regions. See also Solar nebula A molecular cloud, sometimes called a stellar nursery if Star formation is occurring within is a type of Interstellar Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 These begin as irregular dark nebulae, which concentrate and collapse (in volumes determined by the Jeans length) to form compact protostars. A dark nebula is a type of Interstellar cloud that is so dense that it obscures the light from the background emission or Reflection nebula (e Jeans' Length is the critical radius of a cloud (typically a cloud of interstellar dust where thermal energy which causes the cloud to expand is counteracted by gravity which causes [36]
As the more massive stars appear, they transform the cloud into an H II region of glowing gas and plasma. An H II region (also known as Emission nebula) is a cloud of glowing Gas and plasma, sometimes several hundred Light-years across The stellar wind and supernova explosions from these stars eventually serve to disperse the cloud, often leaving behind one or more young open clusters of stars. The solar wind is a Stream of charged particles&mdasha plasma &mdashthat are ejected from the upper atmosphere of the Sun. An open cluster is a group of up to a few thousand Stars that were formed from the same Giant molecular cloud, and are still loosely gravitationally These clusters gradually disperse, and the stars join the population of the Milky Way.
Kinematic studies of matter in the Milky Way and other galaxies have demonstrated that there is more mass than can be accounted for by visible matter. A dark matter halo appears to dominate the mass, although the nature of this dark matter remains undetermined. Most of the mass of any galaxy is dominated by a component concentrated at the centre of the galaxy but dominating its dynamics throughout known as the Dark matter halo. [37]
Extragalactic astronomy
The study of objects outside of our galaxy is a branch of astronomy concerned with the formation and evolution of Galaxies; their morphology and classification; and the examination of active galaxies, and the groups and clusters of galaxies. Extragalactic astronomy is the branch of Astronomy concerned with objects outside our own Milky Way Galaxy (the study of all astronomical objects which are not covered The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning the formation of the first galaxies the way Galaxy morphological classification is a system used by Astronomers to divide galaxies into groups based on their visual appearance An active galactic nucleus ( AGN) is a compact region at the centre of a Galaxy which has a much higher than normal luminosity over some or all of the Electromagnetic Galaxy groups and clusters are the largest Gravitationally bound objects to have arisen thus far in the process of cosmic structure formation The latter is important for the understanding of the large-scale structure of the cosmos. In Physical cosmology, the term large-scale structure refers to the characterization of observable distributions of Matter and Light
Most galaxies are organized into distinct shapes that allow for classification schemes. They are commonly divided into spiral, elliptical and Irregular galaxies. A spiral galaxy is a Galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the An elliptical galaxy is a Galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble (whose name was dedicated An irregular galaxy is a Galaxy that does not fall into any of the regular classes of the Hubble sequence. [38]
As the name suggests, an elliptical galaxy has the cross-sectional shape of an ellipse. In Mathematics, an ellipse (from the Greek ἔλλειψις literally absence) is a Conic section, the locus of points in a The stars move along random orbits with no preferred direction. Randomness is a lack of order Purpose, cause, or predictability These galaxies contain little or no interstellar dust; few star-forming regions; and generally older stars. Elliptical galaxies are more commonly found at the core of galactic clusters, and may be formed through mergers of large galaxies.
A spiral galaxy is organized into a flat, rotating disk, usually with a prominent bulge or bar at the center, and trailing bright arms that spiral outward. The arms are dusty regions of star formation where massive young stars produce a blue tint. Spiral galaxies are typically surrounded by a halo of older stars. Both the Milky Way and the Andromeda Galaxy are spiral galaxies. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply The Andromeda Galaxy (ænˈdrɒmədə also known as Messier 31, M31, or NGC 224; often referred to as the Great Andromeda
Irregular galaxies are chaotic in appearance, and are neither spiral nor elliptical. About a quarter of all galaxies are irregular, and the peculiar shapes of such galaxies may be the result of gravitational interaction.
An active galaxy is a formation that is emitting a significant amount of its energy from a source other than stars, dust and gas; and is powered by a compact region at the core, usually thought to be a super-massive black hole that is emitting radiation from in-falling material.
A radio galaxy is an active galaxy that is very luminous in the radio portion of the spectrum, and is emitting immense plumes or lobes of gas. Radio galaxies and their relatives radio-loud Quasars and Blazars, are types of Active galaxy that are very luminous at radio wavelengths (up Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. Active galaxies that emit high-energy radiation include Seyfert galaxies, Quasars, and Blazars. Seyfert galaxies are a class of galaxies with nuclei that produce Spectral line emission from highly Ionized gas named after Carl Keenan Seyfert A quasar (contraction of QUASi-stellAR radio source) is an extremely powerful and distant Active galactic nucleus. A blazar is a very compact and highly variable energy source associated with a presumed Supermassive black hole at the center of a Host galaxy. Quasars are believed to be the most consistently luminous objects in the known universe. [39]
The large-scale structure of the cosmos is represented by groups and clusters of galaxies. In Physical cosmology, the term large-scale structure refers to the characterization of observable distributions of Matter and Light This structure is organized in a hierarchy of groupings, with the largest being the superclusters. Superclusters are large groupings of smaller galaxy groups and clusters, and are among the largest structures of the Cosmos. The collective matter is formed into filaments and walls, leaving large voids in between. In Physical cosmology, filaments are the largest known structures in the Universe, thread-like structures with a typical length of 50 to 80 ''h''-1 In Astronomy, voids are the empty spaces between filaments, the largest-scale structures in the Universe, that contain very few or no galaxies [40]
Cosmology
Cosmology (from the Greek κοσμος "world, universe" and λογος "word, study") could be considered the study of the universe as a whole. Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its
Observations of the large-scale structure of the universe, a branch known as physical cosmology, have provided a deep understanding of the formation and evolution of the cosmos. In Physical cosmology, the term large-scale structure refers to the characterization of observable distributions of Matter and Light The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its Fundamental to modern cosmology is the well-accepted theory of the big bang, wherein our universe began at a single point in time, and thereafter expanded over the course of 13. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. The metric expansion of space is the averaged increase of metric (i 7 Gyr to its present condition. The concept of the big bang can be traced back to the discovery of the microwave background radiation in 1965.
In the course of this expansion, the universe underwent several evolutionary stages. In the very early moments, it is theorized that the universe experienced a very rapid cosmic inflation, which homogenized the starting conditions. In Physical cosmology, cosmic inflation is the idea that the nascent Universe passed through a phase of exponential expansion that Thereafter, nucleosynthesis produced the elemental abundance of the early universe. In Physical cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than those of H-1 (i (See also nucleocosmochronology. Nucleocosmochronology, also known as cosmochronology, is a relatively new technique used to determine timescales for astrophysical objects and events )
When the first atoms formed, space became transparent to radiation, releasing the energy viewed today as the microwave background radiation. The expanding universe then underwent a Dark Age due to the lack of stellar energy sources. [41]
A hierarchical structure of matter began to form from minute variations in the mass density. Matter accumulated in the densest regions, forming clouds of gas and the earliest stars. In Astronomy and Physical cosmology, the metallicity of an object is the proportion of its matter made up of Chemical elements other than Hydrogen These massive stars triggered the reionization process and are believed to have created many of the heavy elements in the early universe. In Big Bang cosmology, reionization is the process that reionized the matter in the Universe after the " dark ages.
Gravitational aggregations clustered into filaments, leaving voids in the gaps. Gradually, organizations of gas and dust merged to form the first primitive galaxies. Over time, these pulled in more matter, and were often organized into groups and clusters of galaxies, then into larger-scale superclusters. Galaxy groups and clusters are the largest Gravitationally bound objects to have arisen thus far in the process of cosmic structure formation [42]
Fundamental to the structure of the universe is the existence of dark matter and dark energy. In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from In Physical cosmology, dark energy is a hypothetical exotic form of Energy that permeates all of space and tends to increase the rate of expansion of the universe These are now thought to be the dominant components, forming 96% of the density of the universe. For this reason, much effort is expended in trying to understand the physics of these components. [43]
Interdisciplinary studies
Astronomy and astrophysics have developed significant interdisciplinary links with other major scientific fields. These include:
- Astrobiology: the study of the advent and evolution of biological systems in the universe. Astrobiology (from Greek grc ἄστρον astron, "constellation star" grc βίος bios, "life" and grc -λογία
- Archaeoastronomy: the study of ancient or traditional astronomies in their cultural context, utilizing archaeological and anthropological evidence. Archaeoastronomy (also spelled archeoastronomy) is the study of how peoples in the past "have understood the phenomena in the sky how they used phenomena Archaeology, archeology, or archæology (from Greek grc ἀρχαιολογία archaiologia – grc ἀρχαῖος archaīos Anthropology (/ˌænθɹəˈpɒlədʒi/ from Greek grc ἄνθρωπος anthrōpos, "human" -λογία -logia) is the study of
- Astrochemistry: the study of the chemicals found in space, usually in molecular clouds, and their formation, interaction and destruction. Astrochemistry is the study of the Chemical elements found in outer space generally on larger scales than the Solar System, particularly in molecular gas clouds A chemical substance is a Material with a definite chemical composition. See also Solar nebula A molecular cloud, sometimes called a stellar nursery if Star formation is occurring within is a type of Interstellar It represents an overlap of the disciplines of astronomy and chemistry.
- Cosmochemistry: the study of the chemicals found within the Solar System, including the origins of the elements and variations in the isotope ratios. Cosmochemistry is concerned with the origin and development of the elements and their Isotopes primarily within the Solar System. The Solar System consists of the Sun and those celestial objects bound to it by Gravity. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides
Amateur astronomy
Collectively, amateur astronomers observe a variety of celestial objects and phenomena sometimes with equipment that they build themselves. The field of amateur telescope making is considered an offshoot of the Amateur astronomy community Common targets of amateur astronomers include the Moon, planets, stars, comets, meteor showers, and a variety of deep-sky objects such as star clusters, galaxies, and nebulae. Deep sky or Deep Sky Object (DSO for short which differs from Deep space, is a term used by amateur astronomers to describe mostly faint Astronomical objects outside One branch of amateur astronomy, amateur astrophotography, involves the taking of photos of the night sky. Astrophotography is a specialized type of Photography that entails making photographs of astronomical objects in the sky such as the Moon, Sun, Planets Many amateurs like to specialize in the observation of particular objects, types of objects, or types of events which interest them. [44][45]
Most amateurs work at visible wavelengths, but a small minority experiment with wavelengths outside the visible spectrum. This includes the use of infrared filters on conventional telescopes, and also the use of radio telescopes. The pioneer of amateur radio astronomy was Karl Jansky who started observing the sky at radio wavelengths in the 1930s. Karl Guthe Jansky ( October 22, 1905 &ndash February 14, 1950) was an American Physicist and Radio Engineer A number of amateur astronomers use either homemade telescopes or use radio telescopes which were originally built for astronomy research but which are now available to amateurs (e. g. the One-Mile Telescope). The One-Mile Telescope at the Mullard Radio Astronomy Observatory (MRAO was completed by the Radio Astronomy Group of Cambridge University in 1964 [46][47]
Amateur astronomers continue to make scientific contributions to the field of astronomy. Indeed, it is one of the few scientific disciplines where amateurs can still make significant contributions. Amateurs can make occultation measurements that are used to refine the orbits of minor planets. They can also discover comets, and perform regular observations of variable stars. Improvements in digital technology have allowed amateurs to make impressive advances in the field of astrophotography. [48][49][50]
Major questions in astronomy
- See also: Unsolved problems in physics
Although the scientific discipline of astronomy has made tremendous strides in understanding the nature of the universe and its contents, there remain some important unanswered questions. This is a list of some of the major unsolved problems in Physics. Answers to these may require the construction of new ground- and space-based instruments, and possibly new developments in theoretical and experimental physics.
- What is the origin of the stellar mass spectrum? That is, why do astronomers observe the same distribution of stellar masses—the initial mass function—apparently regardless of the initial conditions?[51] A deeper understanding of the formation of stars and planets is needed. The initial mass function (IMF is an Empirical function that describes the Mass distribution (the histogram of stellar masses of a population of stars in terms
- Is there other life in the Universe? Especially, is there other intelligent life? If so, what is the explanation for the Fermi paradox? The existence of life elsewhere has important scientific and philosophical implications. Extraterrestrial life is Life originating outside of the Earth. The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for [52][53]
- What is the nature of dark matter and dark energy? These dominate the evolution and fate of the cosmos, yet we are still uncertain about their true natures. [54]
- Why did the universe come to be? Why, for example, are the physical constants so finely tuned that they permit the existence of life? Could they be the result of cosmological natural selection? What caused the cosmic inflation that produced our homogeneous universe?[55]
- What will be the ultimate fate of the universe?[56]
See also
- Astrology and astronomy
- Astronomer
- Astrophysics Data System
- Category:Ancient astronomy
- Category:Astronomical observatories
- Category:Astronomy organizations
- Category:Astronomy timelines
- Cosmogony
- Extragalactic Distance Scale
- International Year of Astronomy
- List of basic astronomy topics
- Solar System
- Space exploration
- Space science
References
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- ^ Lerner & K. Lee Lerner, Brenda Wilmoth (2006). Environmental issues : essential primary sources.". Thomson Gale. Retrieved on 2006-09-11. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 9 - The Battle of the Teutoburg Forest ends 506 - The Bishops of Visigothic Gaul
- ^ Pogge, Richard W. (1997). The Once & Future Sun (lecture notes). New Vistas in Astronomy. Retrieved on 2005-12-07. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Events 43 BC - Marcus Tullius Cicero assassinated 1696 - Connecticut Route 108, one of the oldest highways
- ^ D. P. Stern, M. Peredo (2004-09-28). "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " Events 48 BC - Pompey the Great is assassinated on orders of King Ptolemy of Egypt after landing in Egypt. The Exploration of the Earth's Magnetosphere. NASA. Retrieved on 2006-08-22. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 392 - Arbogast has Eugenius elected Western Roman Emperor.
- ^ J. F. Bell III, B. A. Campbell, M. S. Robinson (2004). Remote Sensing for the Earth Sciences: Manual of Remote Sensing, 3rd, John Wiley & Sons. Retrieved on 2006-08-23. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 79 - Mount Vesuvius begins stirring on the feast day of Vulcan the Roman god of fire
- ^ E. Grayzeck, D. R. Williams (2006-05-11). Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 330 - Byzantium is renamed ''Nova Roma'' during a dedication ceremony but is more popularly referred to as Constantinople Lunar and Planetary Science. NASA. Retrieved on 2006-08-21. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 1192 - Minamoto Yoritomo becomes Seii Tai Shōgun and the De facto ruler of Japan.
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- ^ Ott, Thomas (2006-08-24). Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 49 BC - Julius Caesar 's General Gaius Scribonius Curio is defeated in the Second Battle of the Bagradas River The Galactic Centre. Max-Planck-Institut für extraterrestrische Physik. Retrieved on 2006-09-08. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 70 - Roman forces under Titus sack Jerusalem. 1264 - The Statute of Kalisz
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- ^ Was the Universe Designed?. Counterbalance Meta Library. Retrieved on 2006-08-12. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 1099 - First Crusade: Battle of Ascalon - Crusaders under the command of Godfrey of Bouillon defeat Fatimid
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Wish to suggest The Collapsing Universe The Story of Black Holes by Isaac Asimov ISBN 0-671-49886-X WFPMWFPM (talk) 04:45, 19 May 2008 (UTC)
External links
- http://www.nasa.gov/
- International Year of Astronomy 2009 IYA2009 Main website
- Cosmic Journey: A History of Scientific Cosmology from the American Institute of Physics
- Astronomy Picture of the Day
- Southern Hemisphere Astronomy
- Sky & Telescope publishers
- Astronomy Magazine
- Universe Today for astronomy and space-related news
- Celestia Motherlode Educational site for Astronomical journeys through space
- Hubblesite.org - home of NASA's Hubble Space Telescope
- Astronomy - A History - G. Forbes - 1909 (eLibrary Project - eLib Text)
- (historical)
- Prof. Sir Harry Kroto, NL, Astrophysical Chemistry Lecture Series. 8 Freeview Lectures provided by the Vega Science Trust.
- Core books and core journals in Astronomy, from the Smithsonian/NASA Astrophysics Data System
The NASA Astrophysics Data System (usually referred to as ADS) is an online database of over 7000000 Astronomy and Physics papers from both
Dictionary
astronomy
-noun
- The study of the physical universe beyond the Earth's atmosphere, including the process of mapping locations and properties of the matter and radiation in the universe.
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