Eta2 Hydri

From Wikipedia, the free encyclopedia
  (Redirected from HD 11977)
Jump to: navigation, search
Eta2 Hydri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hydrus
Right ascension 01h 54m 56.132s[1]
Declination –67° 38′ 50.29″[1]
Apparent magnitude (V) +4.68
Characteristics
Spectral type G8.5III
B−V color index 0.931
Variable type Suspected
Astrometry
Radial velocity (Rv) –16.2 km/s
Proper motion (μ) RA: 76.22 ± 0.14[1] mas/yr
Dec.: 72.94 ± 0.17[1] mas/yr
Parallax (π) 14.91 ± 0.16[1] mas
Distance 219 ± 2 ly
(67.1 ± 0.7 pc)
Absolute magnitude (MV) 0.57 ± 0.07[2]
Details
Mass 1.87 ± 0.30[2] M
Radius 10.2 ± 0.5[2] R
Surface gravity (log g) 2.66 ± 0.10[2] cgs
Temperature 4,975[2] K
Metallicity [Fe/H] –0.21[2] dex
Age 1.30 ± 0.48[2] Gyr
Other designations
HD 11977, HIP 8928, HR 570
Database references
SIMBAD data

Eta2 Hydri2 Hyi, η2 Hydri), often catalogued as HD 11977, is a giant yellow star approximately 219[1] light-years away in the constellation of Hydrus. Based on its mass, it was probably a class A star (similar to Vega or Fomalhaut) when it was on the main sequence, though it is now in the giant stage of its evolution. It is thought to be around 1.3 billion years old and has expanded to 10 times the Sun's diameter, though is only around 1.8 times as massive as the Sun.[2] As of 2005, an extrasolar planet was confirmed to be orbiting the star.

Planetary system[edit]

In 2005, the giant planet Eta2 Hydri b was found in orbit around Eta2 Hydri.[3]

The Eta2 Hydri planetary system[3]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b >6.54 MJ 1.93 711±8 0.40±0.07

See also[edit]

References[edit]

  1. ^ a b c d e f van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. ^ a b c d e f g h da Silva, L. et al. (November 2006), "Basic physical parameters of a selected sample of evolved stars", Astronomy and Astrophysics 458 (2): 609–623, arXiv:astro-ph/0608160, Bibcode:2006A&A...458..609D, doi:10.1051/0004-6361:20065105 
  3. ^ a b Setiawan et al. (2005). "A substellar companion around the intermediate-mass giant star HD 11977". Astronomy & Astrophysics 437 (2): L31–L34. arXiv:astro-ph/0505510. Bibcode:2005A&A...437L..31S. doi:10.1051/0004-6361:200500133. 

External links[edit]

Coordinates: Sky map 01h 54m 56s, −67° 38′ 50″