HD 149026

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HD 149026
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hercules
Right ascension  16h 30m 29.6185s[1]
Declination +38° 20′ 50.308″[1]
Apparent magnitude (V) 8.15[2]
Spectral type G0 IV[2]
Apparent magnitude (B) 8.76[3]
B−V color index 0.611
Radial velocity (Rv)–18.1 ± 0.4[3] km/s
Proper motion (μ) RA: −77.900±0.075[1] mas/yr
Dec.: 52.694±0.088[1] mas/yr
Parallax (π)13.04 ± 0.22[1] mas
Distance250 ± 4 ly
(77 ± 1 pc)
Absolute magnitude (MV)3.65 ± 0.12[4]
Mass1.345 ± 0.020[4] M
Radius1.541 +0.046
[4] R
Luminosity3.03 +0.20
[4] L
Surface gravity (log g)4.189 +0.020
[4] cgs
Temperature6147 ± 50[2] K
Metallicity [Fe/H]0.36 ± 0.05[2] dex
Rotational velocity (v sin i)6.0 ± 0.5[2] km/s
Age2.6 +0.3
[4] Gyr
Other designations
Ogma, BD+38°2787, GSC 03063-01587, HIP 80838, SAO 65349[3]
Database references
Exoplanet Archivedata
Extrasolar Planets

HD 149026, also named Ogma /ˈɒɡmə/,[5] is a yellow subgiant star approximately 250 light-years from the Sun in the constellation of Hercules. An extrasolar planet (designated HD 149026 b, later named Smertrios) is believed to orbit the star.


HD 149026 in the star's identifier in the Henry Draper Catalog.[3] Following its discovery in 2005 the planet was designated HD 149026 b.

In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets and their host stars.[6] The process involved public nomination and voting for the new names.[7] In December 2015, the IAU announced the winning names were Ogma for this star and Smertrios for its planet.[8]

The winning names based on those submitted by the Club d'Astronomie de Toussaint of France; namely 'Ogmios' and 'Smertrios'. Ogmios was a Gallo-Roman deity and Smertrios was a Gallic deity of war. The IAU substituted the name of Ogma, a deity of eloquence, writing, and great physical strength in the Celtic mythologies of Ireland and Scotland, and who may be related to Ogmios, because 'Ogmios' is the name of an asteroid (189011 Ogmios).[9]

In 2016, the IAU organized a Working Group on Star Names (WGSN)[10] to catalog and standardize proper names for stars. In its first bulletin of July 2016,[11] 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.[5]


The star is thought to be much more massive, larger, and brighter than the Sun. The higher mass means that despite its 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. At a distance of 250 light-years,[1] the star is not visible to the unaided eye. However, it should be easily seen in binoculars or a small telescope.[2]

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.[12]

Planetary system[edit]

In 2005 an unusual extrasolar planet was discovered to be orbiting the star. Designated HD 149026 b, it was detected transiting the star allowing its diameter to be measured. It was found to be smaller than other known transiting planets, meaning it is unusually dense for a closely orbiting giant planet.[2] 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.[13]

The HD 149026 planetary system[14][15][2]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b (Smertrios) 0.324±0.011 MJ 0.042 2.87588874±0.00000059 0.0028+0.019
85.3±0.8° 0.725±0.03 RJ

See also[edit]


  1. ^ a b c d e f Brown, A. G. A; et al. (2016). "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties". Astronomy and Astrophysics. 595. A2. arXiv:1609.04172. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512.Gaia Data Release 1 catalog entry
  2. ^ a b c d e f g h 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.
  3. ^ a b c d "HD 149026". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2009-05-20.
  4. ^ 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.
  5. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016.
  6. ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
  7. ^ NameExoWorlds The Process
  8. ^ Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
  9. ^ NameExoWorlds The Approved Names
  10. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  11. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  12. ^ S.-L. Li; D. N. C. Lin; X.-W. Liu (2008). "Extent of pollution in planet-bearing stars". The Astrophysical Journal. 685 (2): 1210–1219. arXiv:0802.2359. Bibcode:2008ApJ...685.1210L. doi:10.1086/591122.
  13. ^ Imaginova, Sizzling Hot Planet Makes Some Stars Look Cool (5/9/07).
  14. ^ Knutson, Heather A.; et al. (2014). "Friends of Hot Jupiters. I. A Radial Velocity Search for Massive, Long-Period Companions to Close-In Gas Giant Planets". The Astrophysical Journal. 785 (2). 126. arXiv:1312.2954. Bibcode:2014ApJ...785..126K. doi:10.1088/0004-637X/785/2/126.
  15. ^ Zhang, Michael; et al. (2018). "Phase Curves of WASP-33b and HD 149026b and a New Correlation between Phase Curve Offset and Irradiation Temperature". The Astronomical Journal. 155 (2). 83. arXiv:1710.07642. Bibcode:2018AJ....155...83Z. doi:10.3847/1538-3881/aaa458.

External links[edit]

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