| gravity = 4.33[19]
| luminosity = {{val|1.36|0.02}}[16]
| temperature = {{val|5,768|8}}[16]
| metal_fe = +0.20[19]
| rotation = {{nowrap|21.9 ± 0.4 days}}[23]
| age_gyr = {{val|6.1|0.6}}[16]
}}{{Starbox catalog
| names = Helvetios, 51 Peg, GJ 882, HR 8729, BD +19°5036, HD 217014, LTT 16750, GCTP 5568.00, SAO 90896, HIP 113357[25]
}}{{Starbox reference
| Simbad = 51+Peg
| NSTED = 51+Peg
| ARICNS = 01878
| EPE = 51+Peg
}}{{Starbox end}}51 Pegasi (abbreviated 51 Peg), also named Helvetios,[26] is a Sun-like star located {{Convert|50.45|ly|pc|abbr=off|lk=on}} from Earth in the constellation of Pegasus. It was the first main-sequence star found to have an exoplanet (designated 51 Pegasi b, officially named Dimidium, formerly unofficially dubbed Bellerophon) orbiting it.[27]Properties
The star is of apparent magnitude 5.49, and so is visible with the naked eye under suitable viewing conditions.
51 Pegasi was listed as a standard star for the spectral type G2IV in the 1989 The Perkins catalog of revised MK types for the cooler stars. Historically it was generally given a stellar classification of G5V,[17] and even in more modern catalogues it is usually listed as a main-sequence star.[29] It is generally considered to still be generating energy through the thermonuclear fusion of hydrogen at its core, but to be in a more evolved state than the sun.[16] The effective temperature of the chromosphere is about 5571 K, giving 51 Pegasi the characteristic yellow hue of a G-type star.[31] It is estimated to be 6.1–8.1 billion years old, somewhat older than the Sun, with a radius 24% larger and 11% more massive. The star has a higher proportion of elements other than hydrogen/helium compared to the Sun; a quantity astronomers term a star's metallicity. Stars with higher metallicity such as this are more likely to host planets.[17] In 1996 astronomers Baliunas, Sokoloff, and Soon measured a rotational period of 37 days for 51 Pegasi.[33]
Although the star was suspected of being variable during a 1981 study,[34] subsequent observation showed there was almost no chromospheric activity between 1977 and 1989. Further examination between 1994 and 2007 showed a similar low or flat level of activity. This, along with its relatively low X-ray emission, suggests that the star may be in a Maunder minimum period[17] during which a star produces a reduced number of star spots.
The star rotates at an inclination of 79{{±|11|30}} degrees relative to Earth.[23]
Nomenclature
51 Pegasi is the Flamsteed designation. On its discovery, the planet was designated 51 Pegasi b by its discoverers and unofficially dubbed Bellerophon by the astronomer Geoffrey Marcy, in keeping with the convention of naming planets after Greek and Roman mythological figures (Bellerophon was a figure from Greek mythology who rode the winged horse Pegasus).[37]
In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets and their host stars.[38] The process involved public nomination and voting for the new names.[39] In December 2015, the IAU announced the winning names were Helvetios for this star and Dimidium for its planet.[40]
The winning names were those submitted by the Astronomische Gesellschaft Luzern, Switzerland. 'Helvetios' is Latin for 'the Helvetian' and refers to the Celtic tribe that lived in Switzerland during antiquity; 'Dimidium' is Latin for 'half', referring to the planet's mass of at least half the mass of Jupiter.[41]
In 2016, the IAU organized a Working Group on Star Names (WGSN)[42] to catalog and standardize proper names for stars. In its first bulletin of July 2016,[43] the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.[26]
Planetary system
{{main|51 Pegasi b}}On October 6, 1995, Swiss astronomers Michel Mayor and Didier Queloz announced the discovery of an exoplanet orbiting 51 Pegasi.[27] The discovery was made at Observatoire de Haute-Provence in France.
51 Pegasi b (51 Peg b) was the first discovered planetary-mass companion of a main-sequence parent star. It orbits very close to the star, experiences estimated temperatures around 1200 °C, and has a mass at least half that of Jupiter. At the time of its discovery, this close distance was not compatible with theories of planet formation and resulted in discussions of planetary migration.[46] However, several hot Jupiters are now known to be oblique relative to the stellar axis.[47]{{Clear}}{{OrbitboxPlanet begin
| table_ref = [48] }}{{OrbitboxPlanet
| exoplanet = b (Dimidium)
| mass = {{nowrap|≥ 0.472 ± 0.039}}
| period = {{nowrap|4.230785 ± 0.000036}}
| semimajor = {{nowrap|0.0527 ± 0.0030}}
| eccentricity = {{nowrap|0.013 ± 0.012}}
}}{{Orbitbox end}}See also
{{col-begin}}{{col-break}}- Star systems
- PSR 1257+12
- 55 Cancri
- 70 Virginis
- 47 Ursae Majoris
- Upsilon Andromedae
- Tau Boötis
{{col-break}}- Other articles
- List of extrasolar planets
- Solar twin
- Portal
{{col-end}}References
1. ^1 {{cite journal | last1=Baliunas | first1=Sallie | last2=Sokoloff | first2=Dmitry | last3=Soon | first3=Willie | title=Magnetic Field and Rotation in Lower Main-Sequence Stars: An Empirical Time-Dependent Magnetic Bode's Relation? | journal=The Astrophysical Journal Letters | volume=457 | issue=2 | date=1996 | pages=L99–L102 | doi=10.1086/309891 | bibcode=1996ApJ...457L..99B }}
2. ^1 2 {{cite journal | last1=Mayor | first1=Michael | last2=Queloz | first2=Didier | title=A Jupiter-mass companion to a solar-type star | journal=Nature | date=1995 | volume=378 | issue=6555 | pages=355–359 | doi=10.1038/378355a0 | bibcode = 1995Natur.378..355M }}
3. ^1 {{cite journal | display-authors=1 | last1=Butler | first1=R. P. | last2=Wright | first2=J. T. | last3=Marcy | first3=G. W. | last4=Fischer | first4=D. A. | last5=Vogt | first5=S. S. | last6=Tinney | first6=C. G. | last7=Jones | first7=H. R. A. | last8=Carter | first8=B. D. | last9=Johnson | first9=J. A. | title=Catalog of Nearby Exoplanets | journal=The Astrophysical Journal | volume=646 | issue=1 | pages=505–522 | date=2006 | doi=10.1086/504701 | bibcode=2006ApJ...646..505B | arxiv=astro-ph/0607493 }}
4. ^1 2 3 4 5 {{cite journal | display-authors=1 | last1=Monet | first1=David G. | last2=Levine | first2=Stephen E. | last3=Canzian | first3=Blaise | last4=Ables | first4=Harold D. | last5=Bird | first5=Alan R. | last6=Dahn | first6=Conard C. | last7=Guetter | first7=Harry H. | last8=Harris | first8=Hugh C. | last9=Henden | first9=Arne A. | title=The USNO-B Catalog | journal=The Astronomical Journal | volume=125 | issue=2 | pages=984–993 | doi=10.1086/345888 | bibcode=2003AJ....125..984M |arxiv = astro-ph/0210694 |date=February 2003}}
5. ^1 2 {{cite journal | display-authors=1 | last1=Frasca | first1=A. | last2=Covino | first2=E. | last3=Spezzi | first3=L. | last4=Alcalá | first4=J. M. | last5=Marilli | first5=E. | last6=Fżrész | first6=G. | last7=Gandolfi | first7=D. | title=REM near-IR and optical photometric monitoring of pre-main sequence stars in Orion. Rotation periods and starspot parameters | journal=Astronomy and Astrophysics | volume=508 | issue=3 | pages=1313–1330 | doi=10.1051/0004-6361/200913327 | bibcode=2009A&A...508.1313F |date=December 2009| arxiv=0911.0760 }}
6. ^1 2 3 4 5 {{Cite Gaia DR2|2835207319109249920}}
7. ^1 {{cite web | title=51 Peg – Star suspected of Variability | work=SIMBAD | publisher=Centre de Données astronomiques de Strasbourg | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=51+Pegasi | accessdate=2011-12-17 }}
8. ^1 2 {{cite journal | display-authors=1 | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | pages=99 | date=1966 | bibcode=1966CoLPL...4...99J }}
9. ^1 {{Cite journal | display-authors=1 | last1=Kukarkin | first1=B. V. | last2=Kholopov | first2=P. N. | last3=Artiukhina | first3=N. M. | last4=Fedorovich | first4=V. P. | last5=Frolov | first5=M. S. | last6=Goranskij | first6=V. P. | last7=Gorynya | first7=N. A. | last8=Karitskaya | first8=E. A. | last9=Kireeva | first9=N. N. | title=Nachrichtenblatt der Vereinigung der Sternfreunde e.V. (Catalogue of suspected variable stars) | journal=Nachrichtenblatt der Vereinigung der Sternfreunde | pages=0 | date=1981 | bibcode=1981NVS...C......0K }}
10. ^1 2 3 4 {{citation | display-authors=1 | last1=Poppenhäger | first1=K. | last2=Robrade | first2=J. | last3=Schmitt | first3=J. H. M. M. | last4=Hall | first4=J. C. | title=51 Pegasi – a planet-bearing Maunder minimum candidate | journal=Astronomy and Astrophysics | volume=508 | issue=3 | pages=1417–1421 | doi=10.1051/0004-6361/200912945 | bibcode=2009A&A...508.1417P |arxiv = 0911.4862 |date=December 2009}}
11. ^1 2 {{citation | display-authors=1 | last1=Simpson | first1=E. K. | last2=Baliunas | first2=S. L. | last3=Henry | first3=G. W. | last4=Watson | first4=C. A. | title=Rotation periods of exoplanet host stars | journal=Monthly Notices of the Royal Astronomical Society | volume=408 | issue=3 | pages=1666–1679 | doi=10.1111/j.1365-2966.2010.17230.x | bibcode=2010MNRAS.408.1666S |arxiv = 1006.4121 |date=November 2010}} [as "HD 217014"]
12. ^1 {{cite web|title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |accessdate=2012-01-16 |deadurl=yes |archiveurl=https://www.webcitation.org/6630AbtJZ?url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archivedate=March 10, 2012}}
13. ^1 {{cite journal|bibcode=1989ApJS...71..245K|title=The Perkins Catalog of Revised MK Types for the Cooler Stars|journal=The Astrophysical Journal Supplement Series|volume=71|pages=245|last1=Keenan|first1=Philip C.|last2=McNeil|first2=Raymond C.|year=1989}}
14. ^1 {{cite journal|bibcode=2014yCat....1.2023S|title=VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2016)|journal=VizieR On-line Data Catalog|last1=Skiff|first1=B. A.|year=2014}}
15. ^1 2 3 4 5 {{cite journal|doi=10.1051/0004-6361/201527542|bibcode=2016A&A...591A..89M|arxiv=1607.01279|title=Chromospheric activity and evolutionary age of the Sun and four solar twins|journal=Astronomy & Astrophysics|volume=591|pages=A89|year=2016|last1=Mittag|first1=M.|last2=Schröder|first2=K.-P.|last3=Hempelmann|first3=A.|last4=González-Pérez|first4=J. N.|last5=Schmitt|first5=J. H. M. M.}}
16. ^1 {{Cite web|url=http://exoplanet.eu/catalog/51_peg_b/|title=51_peg_b|publisher= Extrasolar Planet Encyclopaedia|accessdate=November 12, 2012}}
17. ^1 2 {{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |accessdate=28 July 2016}}
18. ^1 {{cite web|url=http://www.berkeley.edu/news/media/releases/96legacy/releases.96/14301.html |title=University of California at Berkeley News Release |date=1996-11-17 |accessdate=2018-09-27}}
19. ^1 {{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|accessdate=22 May 2016}}
20. ^1 {{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 1 |accessdate=28 July 2016}}
21. ^1 {{cite journal|title=Starspots and spin-orbit alignment for Kepler cool host stars|journal=Astronomische Nachrichten|volume=334|issue=1–2|pages=180|author=Roberto Sanchis-Ojeda|author2=Josh N. Winn|author3=Daniel C. Fabrycky|date=2012|arxiv=1211.2002|bibcode = 2013AN....334..180S |doi = 10.1002/asna.201211765 |citeseerx=10.1.1.759.5082}}
22. ^1 {{cite press release|url=http://www.iau.org/news/pressreleases/detail/iau1404/ |title=NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars] |publisher=IAU |date=9 July 2014 |accessdate=2018-09-27}}
23. ^1 {{cite web|url=http://nameexoworlds.iau.org/process |title=NameExoWorlds The Process |accessdate=2018-09-27}}
24. ^1 {{cite press release |url=http://www.iau.org/news/pressreleases/detail/iau1514/ |title=Final Results of NameExoWorlds Public Vote Released] |publisher=International Astronomical Union |date=15 December 2015 |accessdate=2018-09-27}}
25. ^1 {{cite web| url=http://nameexoworlds.iau.org/names |title=NameExoWorlds The Approved Names |accessdate=2018-09-27}}