Rigel, Beta Ori

Rigel is the lower right star in the rectangle of bright stars in Orion. Orion (ɒˈraɪən a Constellation often referred to as The Hunter, is a prominent constellation one of the largest and perhaps the best-known and most conspicuous
Observation data Epoch J2000. In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. 0
Constellation (pronunciation)	Orion
Right ascension	05h 14m 32. In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Each culture has its own Constellations usually based on Mythology. Orion (ɒˈraɪən a Constellation often referred to as The Hunter, is a prominent constellation one of the largest and perhaps the best-known and most conspicuous Right ascension (abbrev RA; symbol α) is the Astronomical term for one of the two Coordinates of a point on the Celestial sphere 272s[1]
Declination	−08° 12′ 05. In Astronomy, declination (abbrev dec or δ) is one of the two coordinates of the Equatorial coordinate system, the other being either 91″[1]
Apparent magnitude (V)	0. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 18[1]
Characteristics
Spectral type	B8Iab[2]
U-B color index	−0. In Astronomy, stellar classification is a classification of Stars based initially on photospheric temperature and its associated Spectral characteristics In Astronomy, the color index is a simple numerical expression that determines the color of an object which in the case of a Star gives its Temperature 66
B-V color index	−0. In Astronomy, the color index is a simple numerical expression that determines the color of an object which in the case of a Star gives its Temperature 03
Variable type	Slightly irregular
Astrometry
Radial velocity (Rv)	20. For the astronomical object see Variable star. Variable Star is a 2006 novel written by Spider Robinson Astrometry is the branch of Astronomy that relates to precise measurements and explanations of the positions and movements of Stars and other celestial bodies Radial velocity is the Velocity of an object in the direction of the line of sight (i 7[2] km/s
Proper motion (μ)	RA: 1. 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 87[1] mas/yr Dec. A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60 of one degree. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun : −0. 56[1] mas/yr
Parallax (π)	4. A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60 of one degree. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun 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 22 ± 0. 81 mas
Distance	approx. A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60 of one degree. Distance is a numerical description of how far apart objects are 800 ly (approx. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by 240 pc)
Absolute magnitude (MV)	−6. History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838 In Astronomy, absolute magnitude (also known as absolute visual magnitude) is the Apparent magnitude an object would have if it were at a standard 7
Details
Mass	17 M☉
Radius	70 R☉
Luminosity	66,000(bolometric) L☉
Temperature	11,000 K
Other designations
β Orionis, 19 Ori, Algebar; Elgebar, HD 34085, HR 1713, HIP 24436, SAO 131907
Database references
SIMBAD	data

Artist's rendition of Rigel as viewed from a distance of 1 AU

Rigel (pronounced /ˈraɪʤəl/) (β Orionis, beta Ori) is the brightest star in the constellation Orion and the sixth brightest star in the sky, with visual magnitude 0. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. Remote Authentication Dial In User Service ( RADIUS) is a networking protocol that provides centralized access authorization and accounting management for people or computers 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. Luminosity has different meanings in several different fields of science The solar luminosity, L_\odot is a unit of Luminosity ( power emitted in the form of Photons conventionally used by Astronomers to 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 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 A star catalogue, or star catalog, is an Astronomical catalogue that lists Stars In Astronomy, many stars are referred to simply by catalogue The Henry Draper Catalogue ( HD) is an Astronomical Star catalogue published between 1918 and 1924 giving Spectroscopic classifications The Bright Star Catalogue, also known as the Yale Catalogue of Bright Stars or Yale Bright Star Catalogue, is a Star catalogue that lists of all stars of The Hipparcos and Tycho Catalogues (Tycho-1 are the primary products of the European Space Agency 's astrometric mission Hipparcos. For the missile mounting see Mistral missile SIMBAD (the S et of I dentifications M easurements and B ibliography for The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the Orion (ɒˈraɪən a Constellation often referred to as The Hunter, is a prominent constellation one of the largest and perhaps the best-known and most conspicuous Bright stars are bright because they have high luminosities and/or they are nearby The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 18. Although it has the Bayer designation "beta", it is almost always brighter than Alpha Orionis (Betelgeuse). A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Betelgeuse (ˈbiːtəldʒuːz or /ˈbɛtəldʒuːz/ ( α Ori α Orionis Alpha Orionis is a Semiregular variable star located 640 Light-years away from

Physical properties

Rigel is well beyond the current range of accurate parallax measurements; spectroscopic estimates place its distance between 700 and 900 light years, while Hipparcos' "best guess" is 773 light years (237 parsecs), with a margin of error of about 19%. 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 Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by Hipparcos (an Acronym for Hi gh P recision Par allax Co llecting S atellite) was an Astrometry mission History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838 The margin of error is a statistic expressing the amount of random Sampling error in a survey 's results Rigel is a B8Iab supergiant at 17 solar masses, it shines with approximately 40,000 times the luminosity of the Sun. Supergiants are among the most massive Stars In the Hertzsprung-Russell diagram they occupy the top region of the diagram The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. Luminosity has different meanings in several different fields of science The Sun (Sol is the Star at the center of the Solar System. ^[3] Rigel is the most luminous star in our local region of the Milky Way; the nearest more powerful star is Deneb, as much as 3300 light years (1000 parsecs) down the Orion Arm. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply Deneb (α Cyg / α Cygni / Alpha Cygni is the brightest Star in the Constellation Cygnus and one of the vertices of the Summer Triangle The Orion Arm is a minor Spiral arm of the Milky Way galaxy The Solar System and Earth are within the Orion Arm

As it is so bright and it is moving through a region of nebulosity, Rigel lights up several dust clouds in its general vicinity, the most notable being the IC 2118 (the Witch Head Nebula). IC 2118 (also known as Witch Head Nebula due to its shape is believed to be an ancient supernova remnant or gas cloud illuminated by nearby supergiant Rigel ^[4] Rigel is also associated with the Orion Nebula, which — while more or less along the same line of sight as the star — is almost twice as far away from Earth. The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a Diffuse nebula situated south of Orion 's Belt Despite the difference in distance, projecting Rigel's path through space for its expected age brings it close to the nebula. As a result, Rigel is sometimes classified as an outlying member of the Orion OB1 Association, along with many of the other bright stars in that region of the sky; more specifically, it is a member of the Taurus-Orion R1 Association, with the OB1 Association reserved for stars closer to the nebula and more recently formed. ^[5]

Rigel is slightly variable, in an irregular way common to supergiants, with a range from 0. 03 to 0. 3 of a magnitude over roughly 22-25 days. A fourth star in the system is sometimes proposed, but it is generally considered that this is a misinterpretation of the main star's variability, which may be caused by physical pulsation of the surface. ^[6]

Spectroscopy

Studies done on Rigel, looking at the Hα lines, have shown a wide variety of configurations. In Physics and Astronomy, H-alpha, also written Hα, is a specific Emission line created by Hydrogen at 6562 It varies from large emission to large absorption. Current studies are underway to determine if there is a pattern.

Rigel is surrounded by a shell of expelled gas, perhaps shed by its pulsations, stellar wind, or both; the issue remains unsolved. A stellar wind is a flow of neutral or charged gas ejected from the upper atmosphere of a Star. ^[7]

System

Rigel has been a known visual binary since at least 1831, when it was first measured by F.G.W. Struve. A binary star is a Star system consisting of two Stars orbiting around their Center of mass. Year 1831 ( MDCCCXXXI) was a Common year starting on Saturday (link will display the full calendar of the Gregorian Calendar (or a Friedrich Georg Wilhelm von Struve (Vasily Yakovlevich Struve ( April 15, 1793 &ndash November 23, 1864 ( Julian calendar Though Rigel B is not particularly faint at magnitude 6. 7, its closeness to Rigel A — which is over 500 times brighter — makes it a challenging target for telescopes smaller than 150 mm (6 in). ^[8] At Rigel's estimated distance, Rigel B is separated from its primary by over 2200 AU; not surprisingly, there has been no sign of orbital movement, though they share the same proper motion. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the 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 ^[9],^[10]

Rigel B is itself a spectroscopic binary system, consisting of two main sequence stars that orbit their center of gravity every 9. A binary star is a Star system consisting of two Stars orbiting around their Center of mass. The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness 8 days. The stars both belong to the spectral class B9V; Rigel B is the more massive of the pair, at 2. 5 versus 1. 9 solar masses. ^[11],^[12]

There was long-running controversy in the late 19th and early 20th century over the possible visible binarity of Rigel B. The 19th century of the Common Era began on January 1, 1801 and ended on December 31, 1900, according to the Gregorian calendar The twentieth century of the Common Era began on A number of experienced observers claimed to see it as a double, while others were unable to confirm it; indeed, the proponents themselves were sometimes unable to duplicate their results. Observations since have ruled out the likelihood of a visible companion to Rigel B. ^[13],^[14]

Etymology and cultural significance

The star's name comes from its location at the "left foot" of Orion. It is a contraction of Riǧl Ǧawza al-Yusra, this being Arabic for "Left Foot of the Central One". Arabic (ar الْعَرَبيّة (informally ar عَرَبيْ) in terms of the number of speakers is the largest living member of the Semitic language Another Arabic name is رجل الجبار riǧl al-ǧabbār, "the foot of the great one" (giant, conqueror, etc. ), which is also the source of the variant name Algebar. It also has the alternative traditional names Algebar or Elgebar, but these are rarely used.

It is known as 参宿七 (Shēnxiù Qī, "The Seventh of the Three Stars") in Chinese. This mathematically questionable name is due to the fact that the Asterism of Three Stars was originally composed of just three stars, all of them in the girdle of the Orion. Later, four more stars were added to this asterism, but the name remained unchanged.

In stellar navigation, Rigel is one of the most important navigation stars, since it is bright, easily located and equatorial, which means it is visible all around the world's oceans. Celestial navigation, also known as astronavigation, is a Position fixing technique that was devised to help sailors cross the featureless oceans without having to A nautical almanac is a publication describing the positions and movements of Celestial bodies for the purpose of enabling navigators to use Celestial navigation

See also

• Rigel in fiction

References

External links

• Bright star Catalogue
• Rigel