Changes

| image          =Pegasus_51_location.png

| image          =Pegasus_51_location.png

| designation    =51 Pegasi<br/>HD 217014<br/>HIP 113357

| designation    =51 Pegasi<br/>HD 217014<br/>HIP 113357

| rightascension  =22^h 57^m 27.98^s  

| rightascension  =22^h 57^m 27.9804^s<ref name=simbad>{{cite web|url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=51%20Pegasi|title=51 Pegasi|accessdate=2019-07-25|work=Simbad Astronomical Database|publisher=simbad.u-strasbg.fr}}</ref><ref name=vizie>Gaia Colaboration. VizieR Online Data Catalog: Gaia DR2 (Gaia Collaboration, 2018). (2018). ''VizieR Online Data Catalog''. [https://ui.adsabs.harvard.edu/#abs/2018yCat.1345....0G/abstract Bibcode:2018yCat.1345....0G]</ref>

| declination    =+20^o 46′ 07.8″

| declination    =+20° 46′ 07.7822″<ref name=simbad/><ref name=vizie/>

| distance        =50.1 ly

| distance        =50.1 ly<ref name=solstation>{{cite web|url=http://www.solstation.com/stars2/51pegasi.htm|title=51 Pegasi|accessdate=2019-07-25|publisher=solstation.com}}</ref>

| constellation  =Pegasus

| constellation  =Pegasus

| type            =Star

| type            =Star

| dimensions      =

| dimensions      =

| magnitude      =Apparent Mag: 5.94<br/>Absolute Mag: 4.51

| magnitude      =Apparent Mag: 5.49<ref name=illinois>{{cite web|url=http://stars.astro.illinois.edu/sow/51peg.html|title=51 Pegasi|accessdate=2019-07-25|work=Stars|author=Jim Kaler|publisher=stars.astro.illinois.edu}}</ref><br/>Absolute Mag: 4.51

| redshift        =

| redshift        =

| radvelocity    =<nowiki>-33.7 km/s</nowiki>

| radvelocity    =<nowiki>-33.24±0.43 km/s</nowiki><ref name=simbad/><ref name=vizie/>

| propmotion      =RA: 207.25 ± 0.31 mas/yr<br/>Dec.: 60.34 ± 0.30 mas/yr

| propmotion      =RA: 207.363 ± 0.31 mas/yr<ref name=simbad/><ref name=vizie/><br/>Dec.: 62.094 mas/yr<ref name=simbad/><ref name=vizie/>

| parallax        =64.07 ± 0.38 mas

| parallax        =64.64 ± 0.12 mas<ref name=simbad/><ref name=vizie/>

}}

}}

'''51 Pegasi''' is a star located 50.1 light years away in the constellation [[Pegasus]], which is known for both being very much like our own sun and for the being the first star system outside our own where an [[extrasolar planet]] was discovered, in 1995.

'''51 Pegasi''' is a [[star]] located 50.1 light years away in the [[constellation]] [[Pegasus]], which is known for both being very much like our own [[sun]] and for the being the first star system outside our own where an [[extrasolar planet]] was discovered, in 1995.<ref name=britannica>{{cite web|url=https://www.britannica.com/place/51-Pegasi|title=51 Pegasi|accessdate=2019-07-25|publisher=britannica.com}}</ref><ref name=journal>

From Earth, the [[star]] has an apparent magnitude of 5.49 allowing it to be seen by the unaided eye under very dark conditions, or with binoculars.

From Earth, the [[star]] has an apparent magnitude of 5.49 allowing it to be seen by the unaided eye under very dark conditions, or with [[binoculars]].

==The Star==

==The Star==

51 Pegasi is a yellow-orange main sequence star of spectral class of G4-5 Va, although it has been previously classified as G2IV-V (meaning either a dwarf or a subgiant). The [[star]] is remarkably similar to our own [[sun]], having 1.06 times the mass, 1.15 to 1.4 times the diameter, and 1.30 times the visual luminosity. The star is also 60% more abundant in elements heavier then [[hydrogen]] and [[helium]] ([[metallicity]]).<ref>http://solstation.com/stars2/51pegasi.htm</ref> 51 Pegasi rotates once every 37 days, somewhat slower then the Sun's 25 day rotation.

51 Pegasi is a yellow-orange main sequence star of spectral class of G4-5 Va, although it has been previously classified as G2IV-V (meaning either a dwarf or a subgiant). The [[star]] is remarkably similar to our own [[sun]], having 1.06 times the mass, 1.15 to 1.4 times the diameter, and 1.30 times the visual luminosity. The star is also 60% more abundant in elements heavier then [[hydrogen]] and [[helium]] ([[metallicity]]).<ref name=solstation/> 51 Pegasi rotates once every 37 days, somewhat slower then the Sun's 25 day rotation.

The star is believed to be farther along on its path of stellar evolution and appears to be running low on its hydrogen fuel needed for [[stellar fusion]]. The star is estimated to be between 7.5 billion and 8.5 billion years of age.<ref>http://www.aip.org/baas/vol_31/030901bas.pdf</ref>

The star is believed to be farther along on its path of stellar evolution and appears to be running low on its hydrogen fuel needed for [[stellar fusion]].

==Planets==

==Planets==

51 Pegasi was the star where the first extrasolar world was discovered using radial-velocity methods; astronomers Michel Mayor and Didier Queloz announced the discovery the Jupiter class gas giant on October 12, 1995.<ref>http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995Natur.378..355M&db_key=AST&high=3b4b5e274020634</ref> Independent confirmation of the world came from [[San Francisco State University]], [[University of California]], and the Lick Observatory. The world is nicknamed "Bellerophon", although its official astronomical designation is ''51 Pegasi b''.<ref>http://jumk.de/astronomie/exoplanets/51-pegasi.shtml</ref>

51 Pegasi was the star where the first extrasolar world was discovered using radial-velocity methods; astronomers Michel Mayor and Didier Queloz announced the discovery the Jupiter class gas giant on October 12, 1995.<ref name=journal/> Independent confirmation of the world came from [[San Francisco State University]], [[University of California]], and the Lick Observatory. The world is nicknamed "Bellerophon", although its official astronomical designation is ''51 Pegasi b''.<ref>{{cite web|url=https://jumk.de/astronomie/exoplanets/51-pegasi.shtml|title=51 Pegasi and Bellerophon|accessdate=2019-07-25|publisher=jumk.de}}</ref>

The planet itself has at least 46 percent of [[Jupiter|Jupiter’s]] mass and maintains a very close orbit of 0.052 AUs from its parent star.   Because of how close the planet is to 51 Pegasi, its orbit only takes 4.2 days to complete. Because of this distance, the world is tidally locked to its parent star. Temperatures are estimated to be 1265K (around 1000 degrees Celsius / 1800 degrees Fahrenheit) on average.   

The planet itself has at least 46 percent of [[Jupiter|Jupiter’s]] mass and maintains a very close orbit of 0.052 AUs from its parent star. Due to how close the planet is to 51 Pegasi, its orbit only takes 4.2 days to complete. Because of this distance, the world is tidally locked to its parent star. Temperatures are estimated to be 1,265&nbsp;[[kelvin]] (around 1,000 degrees Celsius / 1,800 degrees Fahrenheit) on average.   

The world is also remarkable because a world so close to its parent star was not compatible with planet formation theories at the time, and the planet was considered an anomaly.  Since then other such “hot Jupiters” have been discovered challenging astronomers to revise the theories of planetary formation, one way is by studying orbit migration.

The world is also remarkable because a world so close to its parent star was not compatible with planet formation theories at the time, and the planet was considered an anomaly.  Since then other such “hot Jupiters” have been discovered challenging astronomers to revise the theories of planetary formation, one way is by studying orbit migration.

A [[terrestrial planet]] that could maintain liquid water on its surface could hypothetically exist in a [[habitable zone]] that ranges from 1.2 AU to 2.0 AUs away for 51 Pegasi.<ref>http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001AAS...199.0310N&db_key=AST&high=3cab10bb0312474</ref> The star is a target for NASA’s Terrestrial Planet Finder (TPF) and the ESA's Darwin in the future.   

A [[terrestrial planet]] that could maintain liquid water on its surface could hypothetically exist in a [[habitable zone]] that ranges from 1.2 AU to 2.0 AUs away for 51 Pegasi.<ref>

|last2=Musielak |first2=Z. E.

|last3=Cuntz |first3=M.

|display-authors=3

|title=Orbital Stability of Earth-like Planets in Stellar Habitable Zones

|bibcode=2001AAS...199.0310N

|ref=harv

</ref> The star is a target for NASA’s Terrestrial Planet Finder (TPF) and the ESA's Darwin in the future.   

No other worlds are known at this time.

No other worlds are known at this time.

==References==

==References==

{{reflist}}

{{reflist}}

==Links==

==External links==

*[http://exoplanet.eu/ Extrasolar Planets Encyclopaedia]

*[https://exoplanet.eu/ Extrasolar Planets Encyclopaedia]

*[http://exoplanets.org/ ExoPlanets]

*[https://exoplanets.org/ ExoPlanets]

 

 

[[Category:Stars]]