A giant star is a star with substantially larger radius and luminosity than a main sequence star of the same surface temperature. The Hertzsprung-Russell diagram (usually referred to by the abbreviation H-R diagram or HRD, also known as a colour-magnitude diagram, or CMD In Astronomy, stellar classification is a classification of Stars based initially on photospheric temperature and its associated Spectral characteristics Brown dwarfs are sub- stellar objects with a mass below that necessary to maintain Hydrogen -burning Nuclear fusion reactions in their cores as do stars A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool Star, of the Main sequence, either late K A subdwarf star, sometimes denoted by "sd" is Luminosity class VI under the Yerkes spectral classification system The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness Subgiant star is a class of Stars that are slightly brighter than normal Main sequence (dwarf stars of the same spectral class but not as bright as The luminosity class II in the Yerkes spectral classification is given to bright giants. Supergiants are among the most massive Stars In the Hertzsprung-Russell diagram they occupy the top region of the diagram A hypergiant ( luminosity class 0) is a Star with a tremendous Mass and Luminosity, showing signs of a very high rate of mass loss In Astronomy, absolute magnitude (also known as absolute visual magnitude) is the Apparent magnitude an object would have if it were at a standard In Astronomy, absolute magnitude (also known as absolute visual magnitude) is the Apparent magnitude an object would have if it were at a standard In Astronomy, absolute magnitude (also known as absolute visual magnitude) is the Apparent magnitude an object would have if it were at a standard In Astronomy, absolute magnitude (also known as absolute visual magnitude) is the Apparent magnitude an object would have if it were at a standard 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 Remote Authentication Dial In User Service ( RADIUS) is a networking protocol that provides centralized access authorization and accounting management for people or computers Luminosity has different meanings in several different fields of science The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness Star The effective temperature of a Star is the temperature of a Black body with the same luminosity per surface area (\mathcal{F}_{Bol} [1] Typically, giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. In Astronomy, the solar radius is a unit of Length used to express the size of Stars It is equal to the current radius of the Sun. The Sun (Sol is the Star at the center of the Solar System. Stars still more luminous than giants are referred to as supergiants and hypergiants. Supergiants are among the most massive Stars In the Hertzsprung-Russell diagram they occupy the top region of the diagram A hypergiant ( luminosity class 0) is a Star with a tremendous Mass and Luminosity, showing signs of a very high rate of mass loss [2][3] A hot, luminous main sequence star may also be referred to as a giant. The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness [4] Apart from this, because of their large radii and luminosities, giant stars lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsprung-Russell diagram and correspond to luminosity classes II or III. In Astronomy, stellar classification is a classification of Stars based initially on photospheric temperature and its associated Spectral characteristics The Hertzsprung-Russell diagram (usually referred to by the abbreviation H-R diagram or HRD, also known as a colour-magnitude diagram, or CMD [5]
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Formation
A star becomes a giant star after all the hydrogen available for fusion at its core has been depleted and, as a result, it has left the main sequence. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 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 [5] A star whose initial mass is less than approximately 0. 4 solar masses will not become a giant star. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. This is because such stars have their interior thoroughly mixed by convection and therefore continue fusing hydrogen until it is exhausted throughout the star, at which point they become white dwarfs, composed chiefly of helium. Convection in the most general terms refers to the movement of molecules within Fluids (i A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical This exhaustion, however, is predicted to take significantly longer than the lifetime of the Universe up to now. The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy [6]
If a star is more massive than this lower limit, then when it consumes all of the hydrogen in its core available for fusion, the core will begin to contract. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus Hydrogen now fuses to helium in a shell around the helium-rich core, and the portion of the star outside the shell expands and cools. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical During this portion of its evolution, labeled the subgiant branch on the Hertzsprung-Russell diagram, the luminosity of the star remains approximately constant and its surface temperature decreases. Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime Subgiant star is a class of Stars that are slightly brighter than normal Main sequence (dwarf stars of the same spectral class but not as bright as The Hertzsprung-Russell diagram (usually referred to by the abbreviation H-R diagram or HRD, also known as a colour-magnitude diagram, or CMD Luminosity has different meanings in several different fields of science Star The effective temperature of a Star is the temperature of a Black body with the same luminosity per surface area (\mathcal{F}_{Bol} Eventually the star will start to ascend the red giant branch on the Hertzsprung-Russell diagram. A red giant is a luminous Giant star of low or intermediate mass (roughly 0 The Hertzsprung-Russell diagram (usually referred to by the abbreviation H-R diagram or HRD, also known as a colour-magnitude diagram, or CMD At this point the surface temperature of the star, now typically a red giant, will remain approximately constant as its luminosity and radius increase drastically. Star The effective temperature of a Star is the temperature of a Black body with the same luminosity per surface area (\mathcal{F}_{Bol} A red giant is a luminous Giant star of low or intermediate mass (roughly 0 Luminosity has different meanings in several different fields of science The core will continue to contract, raising its temperature. [7], § 5. 9.
If the star's mass, when on the main sequence, was below approximately 0. 5 solar masses, it is thought that it will never attain the central temperatures necessary to fuse helium. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical [8], p. 169. It will therefore remain a hydrogen-fusing red giant until it eventually becomes a helium white dwarf. [7], § 4. 1, 6. 1. Otherwise, when the core temperature reaches approximately 108 K, helium will begin to fuse to carbon and oxygen in the core by the triple-alpha process. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the The triple alpha process is a set of Nuclear fusion reactions by which three Helium nuclei ( Alpha particles are transformed into Carbon. [7],§ 5. 9, chapter 6. The energy generated by helium fusion causes the core to expand. This causes the pressure in the surrounding hydrogen-burning shell to decrease, which reduces its energy-generation rate. The luminosity of the star decreases, its outer envelope contracts again, and the star leaves the red giant branch. A red giant is a luminous Giant star of low or intermediate mass (roughly 0 [9] Its subsequent evolution will depend on its mass. If not very massive, it may be found in the horizontal branch on the Hertzsprung-Russell diagram, or its position in the diagram may move in loops. The horizontal branch ( HB) is a stage of Stellar evolution which immediately follows the Red giant branch in stars whose masses are similar to the Sun's [7], chapter 6. If the star is not heavier than approximately 8 solar masses, it will eventually exhaust the helium at its core and begin to fuse helium in a shell around the core. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. It will then increase in luminosity again as, now an AGB star, it ascends the asymptotic giant branch of the Hertzsprung-Russell diagram. The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass Stars This is a period of Stellar evolution The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass Stars This is a period of Stellar evolution After the star sheds most of its mass, its core will remain as a carbon-oxygen white dwarf. A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. [7], § 7. 1–7. 4.
For main-sequence stars with masses great enough to eventually fuse carbon (approximately 8 solar masses)[7], p. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. 189, this picture must be modified in many ways. These stars do not increase greatly in luminosity after leaving the main sequence, but they will become redder. They may become red supergiants, or mass loss may cause them to become blue supergiants. Supergiants are among the most massive Stars In the Hertzsprung-Russell diagram they occupy the top region of the diagram [10], pp. 33–35; [2] Eventually, they will become white dwarfs composed of oxygen and neon, or will undergo a core-collapse supernova to form neutron stars, or black holes. A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 Type II Supernova, or core-collapse supernova, is a sub-category of cataclysmic Variable stars that results from the internal collapse and violent explosion 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 [7], § 7. 4. 4–7. 8.
Examples
Well-known giant stars of various colors include
- Alcyone (η Tauri), a blue-white (B-type) giant,[11] the brightest star in the Pleiades. Alcyone (η Tau / η Tauri / Eta Tauri is a Star system in the Constellation Taurus. The Pleiades (ˈpliːədiːz or /ˈplaɪədiːz/ also known as M 45, the '''Seven Sisters''', Seven Stars, SED, Matariki [12]
- Thuban (α Draconis), a white (A-type) giant. This article is about the Star Th'uban is an Arabic word for Dragon. [13]
- σ Octantis, a yellow-white (F-type) giant. Sigma Octantis (σ Oct / σ Octantis is a magnitude 56 star in the constellation Octans most notable for being the current South Star. [14]
- α Aurigae Aa, a yellow (G-type) giant, one of the stars making up Capella. Capella (α Aur / α Aurigae / Alpha Aurigae is the brightest star in the Constellation Auriga and eleventh brightest star in the sky [15]
- Pollux (β Geminorum), an orange (K-type) giant. Pollux, also cataloged as Beta Geminorum (β Gem / β Geminorum is an Orange giant Star approximately 34 Light-years away in the Constellation [16]
- Mira (ο Ceti), a red (M-type) giant. Mira, ˈmaɪrə also known as Omicron Ceti (or ο Ceti / ο Cet is a Red giant Star estimated 200-400 Light years away in [17]
References
- ^ Giant star, entry in Astronomy Encyclopedia, ed. Patrick Moore, New York: Oxford University Press, 2002. ISBN 0-19-521833-7.
- ^ a b supergiant, entry in The Encyclopedia of Astrobiology, Astronomy, and Spaceflight, David Darling, on line, accessed May 15, 2007. Events 1252 - Pope Innocent IV issues the Papal bull Ad exstirpanda, which authorizes but also limits the Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
- ^ hypergiant, entry in The Encyclopedia of Astrobiology, Astronomy, and Spaceflight, David Darling, on line, accessed May 15, 2007. Events 1252 - Pope Innocent IV issues the Papal bull Ad exstirpanda, which authorizes but also limits the Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
- ^ Giant star, entry in Cambridge Dictionary of Astronomy, Jacqueline Mitton, Cambridge: Cambridge University Press, 2001. ISBN 0-521-80045-5.
- ^ a b giant, entry in The Facts on File Dictionary of Astronomy, ed. John Daintith and William Gould, New York: Facts On File, Inc. , 5th ed. , 2006. ISBN 0-8160-5998-5.
- ^ Late stages of evolution for low-mass stars, Michael Richmond, lecture notes, Physics 230, Rochester Institute of Technology, accessed online May 16, 2007. Events 1204 - Baldwin IX Count of Flanders is crowned as the first Emperor of the Latin Empire. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
- ^ a b c d e f g Evolution of Stars and Stellar Populations, Maurizio Salaris and Santi Cassisi, Chichester, UK: John Wiley & Sons, Ltd. , 2005. ISBN 0-470-09219-X.
- ^ Structure and Evolution of White Dwarfs, S. O. Kepler and P. A. Bradley, Baltic Astronomy 4, pp. 166–220.
- ^ Giants and Post-Giants, class notes, Robin Ciardullo, Astronomy 534, Penn State University. The Pennsylvania State University (commonly known as Penn State) is a state-related, land-grant, space grant public research University
- ^ Blowing Bubbles in the Cosmos: Astronomical Winds, Jets, and Explosions, T. W. Hartquist, J. E. Dyson, and D. P. Ruffle, New York: Oxford University Press, 2004. ISBN 0195130545.
- ^ Alcyone, entry in SIMBAD, accessed May 16, 2007. For the missile mounting see Mistral missile SIMBAD (the S et of I dentifications M easurements and B ibliography for Events 1204 - Baldwin IX Count of Flanders is crowned as the first Emperor of the Latin Empire. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
- ^ Alcyone at Jim Kaler's STARS, accessed on line May 16, 2007. Events 1204 - Baldwin IX Count of Flanders is crowned as the first Emperor of the Latin Empire. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
- ^ Thuban, entry in SIMBAD, accessed May 16, 2007. For the missile mounting see Mistral missile SIMBAD (the S et of I dentifications M easurements and B ibliography for Events 1204 - Baldwin IX Count of Flanders is crowned as the first Emperor of the Latin Empire. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
- ^ Sigma Octantis, entry in SIMBAD, accessed May 16, 2007. For the missile mounting see Mistral missile SIMBAD (the S et of I dentifications M easurements and B ibliography for Events 1204 - Baldwin IX Count of Flanders is crowned as the first Emperor of the Latin Empire. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
- ^ α Aurigae Aa, entry in SIMBAD, accessed May 16, 2007. For the missile mounting see Mistral missile SIMBAD (the S et of I dentifications M easurements and B ibliography for Events 1204 - Baldwin IX Count of Flanders is crowned as the first Emperor of the Latin Empire. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
- ^ Pollux, entry in SIMBAD, accessed May 16, 2007. For the missile mounting see Mistral missile SIMBAD (the S et of I dentifications M easurements and B ibliography for Events 1204 - Baldwin IX Count of Flanders is crowned as the first Emperor of the Latin Empire. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
- ^ Mira, entry in SIMBAD, accessed May 16, 2007. For the missile mounting see Mistral missile SIMBAD (the S et of I dentifications M easurements and B ibliography for Events 1204 - Baldwin IX Count of Flanders is crowned as the first Emperor of the Latin Empire. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
See also
Multimedia
- Interactive giant star comparison. In Astronomy, a blue giant is a Star with a Spectral type of O or B (thus being noticeably blue in appearance and a luminosity class of III ( giant A hypergiant ( luminosity class 0) is a Star with a tremendous Mass and Luminosity, showing signs of a very high rate of mass loss A red giant is a luminous Giant star of low or intermediate mass (roughly 0 Supergiants are among the most massive Stars In the Hertzsprung-Russell diagram they occupy the top region of the diagram
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