HD 102956 b

HD 102956 b or Isagel is an extrasolar planet discovered in 2010 by a team of American astronomers led by John Johnson using Doppler spectroscopy and the Keck Observatory in Hawaii. HD 102956 b is in the orbit of host star HD 102956. The planet is at least the mass of Jupiter, orbiting every 6.5 days at a distance of 12 million km. HD 202956 b has a very circular orbit.^[1] The system is roughly 399 light years from us.

HD 102956 b / Isagel

Discovery[1]
Discovered by	Johnson et al.
Discovery site	Keck Observatory
Discovery date	2010
Detection method	Doppler spectroscopy
Orbital characteristics[2]
Semi-major axis	0.0807±0.0073 AU
Eccentricity	0.037±0.019
Orbital period (sidereal)	6.49470±0.00019 d
Time of perihelion	2455351.45±0.64 JD
Argument of perihelion	301±33 º
Semi-amplitude	74.6±1.8 m/s
Star	HD 102956
Physical characteristics[2]
Mass	≥0.960±0.023 MJ

HD 102956

HD 102956 located inside the Big Dipper
Observation data Epoch J2000      Equinox J2000
Constellation	Ursa Major
Right ascension	11h 51m 22.5111s[3]
Declination	+57° 38′ 26.6427″[3]
Characteristics
Evolutionary stage	Main sequence
Spectral type	A
Astrometry
Radial velocity (Rv)	−25±83 km/s
Proper motion (μ)	RA: −11.24±0.049[3] mas/yr Dec.: −17.578±0.049[3] mas/yr
Parallax (π)	8.1753±0.0290 mas[3]
Distance	399 ± 1 ly (122.3 ± 0.4 pc)
Absolute magnitude (MV)	2.5
Details
Mass	1.68±0.11 M☉
Radius	4.4±0.1 R☉
Luminosity (visual, LV)	11.6±0.5 L☉
Temperature	5054±44 K
Metallicity [Fe/H]	+0.19±0.04 dex
Rotational velocity (v sin i)	0.30 km/s
Other designations
BD+58 1340, HIP 57820, SAO 28161, TYC 3839-00846-1, 2MASS J11512253+5738267[4]
Database references
SIMBAD	data
Exoplanet Archive	data

Discovery and nomenclature

The name HD 102956 derives directly from the fact that the star is the 102,956th star catalogued in the Henry Draper catalog. The designation of b is given to the first planet orbiting a given star.

The star is one of the 2.5 million brightest stars in the sky and is part of the Tycho-2 Catalogue. It is not visible to the naked eye with an apparent magnitude of 8.

NameExoWorlds

In 2019 this planet was announced as part of the IAU NameExoWorlds project^[5] where it was designated as the planet that will be named by Sweden. The winning proposal was Isagel, from Nobel laureate Harry Martinson's space poem Aniara.^[6]

Host star

HD 102956 (Aniara) is an orange subgiant with a mass and radius of 1.68 M_☉ and 4.4 R_☉, respectively. The surface temperature is about 5,054 K (4,781 °C). The star is 11.6 times brighter than the Sun. The star's age is estimated at 2.3 billion years.