|The red circle marks the position of Helvetios (51 Pegasi) in the constellation Pegasus.|
dates equinox : J2000.0 , epoch : J2000.0
|Right ascension||22 h 57 m 27.98 s|
|declination||+ 20 ° 46 ′ 7.8 ″|
|Apparent brightness||5.46 likes|
|B − V color index||0.67|
|U − B color index||0.21|
|R − I index||0.34|
|Spectral class||G2 IV|
|Radial velocity||(−33.24 ± 0.43) km / s|
|parallax||(64.65 ± 0.12) mas|
|distance||(50.43 ± 0.09) ly
(15.47 ± 0.03) pc
|Visual absolute brightness M vis||+4.51 mag|
|Rec. Share:||(207.36 ± 0.21) mas / a|
|Dec. portion:||(62.09 ± 0.17) mas / a|
|Dimensions||(1.158 ± 0.058) M ☉|
|radius||(1.183 ± 0.059) R ☉|
1.30 L ☉
|Effective temperature||(5793 ± 70) K.|
|Metallicity [Fe / H]||(0.2 ± 0.07)|
|Rotation time||3 - 7 Days|
|Age||(4.0 ± 2.5) 10 9 a|
and catalog entries
Helvetios ( 51 Pegasi ) is a sun-like star in the constellation Pegasus, 50 light-years away . Its apparent brightness is 5.46 mag, so that it can barely be seen with the naked eye on dark nights. Its mass is about 10% higher than that of the sun and it has a greater metallicity than it because its hydrogen supplies are slowly running out.
Around Helvetios, Michel Mayor and Didier Queloz from the Department of Astronomy at the University of Geneva discovered the first planet outside the solar system ( exoplanet ) that orbits a sun-like star. The planet called Dimidium has about 0.46 Jupiter masses and orbits the star in about 4.2 days at a distance of only 0.052 astronomical units (AU). A second planet was suspected.
The star was named Helvetios by the IAU on December 15, 2015 after a public competition to name exoplanets and their central stars . The name proposed by the youth group of the Lucerne Astronomical Society is Latin and refers to the Celtic tribe of the Helvetii , who settled in what is now Switzerland .
- 51 Peg. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed April 20, 2019 .
- Bright Star Catalog
- 51 Peg b. In: Extrasolar Planets Encyclopaedia . Retrieved April 20, 2019 .
- P. E. Kervella, F. Arenou, F. Mignard, F. Thévenin: Stellar and substellar companions of nearby stars from Gaia DR2. Binarity from proper motion anomaly . In: Astronomy & Astrophysics . 623, p. A72. arxiv : 1811.08902 . bibcode : 2019A & A ... 623A..72K . doi : 10.1051 / 0004-6361 / 201834371 .
- University Corporation for Atmospheric Research: Will a Second Planet Be Discovered around 51 Pegasi? - NCAR Data Suggest Not a Giant One. (No longer available online.) Archived from the original on May 7, 2013 ; accessed on May 9, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- International Astronomical Union: NameExoWorlds - The Approved Names. Retrieved January 3, 2016 .
- SolStation.com: 51 Pegasi. Retrieved May 12, 2015 .