HD 149026

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HD 149026
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hercules
Right ascension 16h 30m 29.620s[1]
Declination +38° 20′ 50.31″[1]
Apparent magnitude (V) 8.15
Spectral type G0IV[2]
Apparent magnitude (B) 8.76[2]
B−V color index 0.611
Radial velocity (Rv) –18.1 ± 0.4[2] km/s
Proper motion (μ) RA: –76.27 ± 0.54[1] mas/yr
Dec.: 53.07 ± 0.69[1] mas/yr
Parallax (π) 12.59 ± 0.70[1] mas
Distance 260 ± 10 ly
(79 ± 4 pc)
Absolute magnitude (MV) 3.65 ± 0.12[3]
Mass 1.345 ± 0.020[3] M
Radius 1.541 +0.046
[3] R
Luminosity 3.03 +0.20
[3] L
Surface gravity (log g) 4.189 +0.020
[3] cgs
Temperature 6147 ± 50[4] K
Metallicity [Fe/H] 0.36 ± 0.05[4] dex
Rotational velocity (v sin i) 6.0 ± 0.5[4] km/s
Age 2.6 +0.3
[3] Gyr
Other designations
BD+38°2787, GSC 03063-01587, HIP 80838, SAO 65349
Database references
Exoplanet Archive data
Extrasolar Planets

HD 149026 is a yellow subgiant star approximately 260 light-years away in the constellation of Hercules. The star is thought to be much more massive, larger, and brighter than the Sun. As of 2005, an extrasolar planet has been confirmed to be orbiting the star. The name of this star comes from its identifier in the Henry Draper Catalog.[2]

The star[edit]

The star is thought to be much more massive, larger, and brighter than the Sun. The higher mass of the star causes that despite considerably younger age (2.0 Ga) it is already much more evolved than the Sun. The internal fusion of hydrogen in the core of the star is coming to an end, and it is beginning to evolve towards red gianthood. HD 149026 is about 260 light-years distant,[1] which means the star is not visible to the unaided eye. However, it should be an easy target to binoculars or a small telescope.[4]

The star is over twice as enriched with chemical elements heavier than hydrogen and helium as the Sun. Because of this and the fact that the star is relatively bright, a group of astronomers in N2K Consortium began to study the star. The star's anomalous composition as measured may be surface pollution only, from the intake of heavy-element planetesimals.[5]

Planetary system[edit]

In 2005 they discovered an unusual extrasolar planet orbiting the star. The planet, designated HD 149026 b, was detected transiting the star allowing its diameter to be measured. It was found to be smaller than other known transiting planets, meaning the planet is unusually dense for a closely orbiting giant planet.[4] The temperature of the giant planet is calculated to be 3,700 °F (2,040 °C), generating so much infrared heat that it glows. Scientists believe the planet absorbs nearly all the sunlight and radiates it into space as heat.[6]

The HD 149026 planetary system
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b 0.36 ± 0.03 MJ 0.042 2.8766 ± 0.001 0

The planet and its host star is one of the planetary systems selected by the International Astronomical Union as part of their public process for giving proper names to exoplanets and their host star (where no proper name already exists).[7][8] The process involves public nomination and voting for the new names, and the IAU plans to announce the new names in mid-November 2015.[9]

See also[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 "SIMBAD query result: HIP 80838 -- Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2009-05-20. 
  3. ^ a b c d e f Carter, Joshua A.; et al. (2009). "Near-Infrared Transit Photometry of the Exoplanet HD 149026b". The Astrophysical Journal 696 (1): 241–253. arXiv:0902.1542. Bibcode:2009ApJ...696..241C. doi:10.1088/0004-637X/696/1/241. 
  4. ^ a b c d e Sato, Bun'ei; et al. (2005). "The N2K Consortium. II. A Transiting Hot Saturn around HD 149026 with a Large Dense Core". The Astrophysical Journal 633 (1): 465–473. arXiv:astro-ph/0507009. Bibcode:2005ApJ...633..465S. doi:10.1086/449306. 
  5. ^ S.-L. Li, D. N. C. Lin, and X.-W. Liu (2008). "Extent of pollution in planet-bearing stars". The Astrophysical Journal 685 (2): 1210–1219. arXiv:0802.2359v1. Bibcode:2008ApJ...685.1210L. doi:10.1086/591122. 
  6. ^ Imaginova, Sizzling Hot Planet Makes Some Stars Look Cool (5/9/07).
  7. ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
  8. ^ NameExoWorlds.
  9. ^ NameExoWorlds.

External links[edit]

Coordinates: Sky map 16h 30m 29.619s, +38° 20′ 50.31″