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BD+20° 1790
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Gemini
Right ascension 07h 23m 43.592s
Declination +20° 24′ 58.66″
Apparent magnitude (V) 9.93
Spectral type K5Ve[1]
Apparent magnitude (B) 11.08
Apparent magnitude (R) 9.43
Apparent magnitude (I) 8.9
Apparent magnitude (J) 7.643
Apparent magnitude (H) 7.032
Apparent magnitude (K) 6.879
B−V color index 1.15
V−R color index 0.50
R−I color index 0.5
Radial velocity (Rv) +9.3 km/s
Proper motion (μ) RA: −65.8 mas/yr
Dec.: −228.1 mas/yr
Distance 84.76 ly
(26[1] pc)
Absolute magnitude (MV) 7.86
Mass 0.63[2] M
Radius 0.71[2] R
Luminosity 0.17[2] L
Surface gravity (log g) 4.53[2] cgs
Temperature 4410[2] K
Metallicity 0.30[2]
Rotation 3.59 days
Rotational velocity (v sin i) 10.03[2] km/s
Age 35-80[2][3]million years
Other designations
TYC 1355-214-1, USNO-B1.0 1104-00142035,2MASS J07234358+2024588, 1SWASP J072343.59+202458.6
Database references
Exoplanet Archive data
Extrasolar Planets

BD+20°1790 is a young late orange dwarf star in the constellation Gemini, located nearly 85 light years away from Sun. The star is young and very active and is a member of the AB Doradus Moving Group.[4] The star has also been studied and monitored by SuperWASP group and found to coincide with the ROSAT source 1RXS J072343.6+202500.[5] The planet candidate was announced in December 2009.[2]

Disproven planet[edit]

The Keplerian fit of the RV data suggested an orbital solution for a close-in massive planet with an orbital period of 7.7834 days. Moreover the presence of a close-in massive jovian planet could explain the high level of stellar activity detected.[2] However, further study suggests that this planet may not exist because the radial velocity variations are strongly correlated to stellar activity, suggesting this activity is the cause of the variations.[6] This echoes the similar case of the disproven planet detection around TW Hydrae, which was also found to be due to stellar activity rather than orbital motion.[7]


  1. ^ a b Torres & Quast; Quast, G. R.; Melo, C. H. F.; Sterzik, M. F. (2008). "Young Nearby Loose Associations". Handbook of Star Forming Regions, Volume II: the Southern Sky ASP Monograph Publications 5: 1–757. arXiv:0808.3362. 
  2. ^ a b c d e f g h i j Hernán-Obispo et al.; Gálvez-Ortiz, M. C.; Anglada-Escudé, G.; Kane, S. R.; Barnes, J. R.; de Castro, E.; Cornide, M. (2009). "Evidence of a massive planet candidate orbiting the young active K5V star BD+20 1790". arXiv:0912.2773 [astro-ph.EP].
  3. ^ Carpenter et al.; Bouwman, Jeroen; Mamajek, Eric E.; Meyer, Michael R.; Hillenbrand, Lynne A.; Backman, Dana E.; Henning, Thomas; Hines, Dean C. et al. (2009). "Formation and Evolution of Planetary Systems: Properties of Debris Dust Around Solar-Type Stars". The Astrophysical Journal Supplement 181 (1): 197–226. arXiv:0810.1003. Bibcode:2009ApJS..181..197C. doi:10.1088/0067-0049/181/1/197. 
  4. ^ Lopez-Santiago et al.; Montes, D.; Crespo-Chacón, I.; Fernández-Figueroa, M. J. (2006). "The Nearest Young Moving Groups". The Astrophysical Journal 643 (2): 1160–1165. arXiv:astro-ph/0601573. Bibcode:2006ApJ...643.1160L. doi:10.1086/503183. 
  5. ^ Norton et al.; Wheatley, P. J.; West, R. G.; Haswell, C. A.; Street, R. A.; Collier Cameron, A.; Christian, D. J.; Clarkson, W. I. et al. (2007). "New periodic variable stars coincident with ROSAT sources discovered using SuperWASP". Astronomy and Astrophysics 467 (2): 785–905. arXiv:astro-ph/0702631. Bibcode:2007A&A...467..785N. doi:10.1051/0004-6361:20077084. 
  6. ^ Figueira et al.; Marmier; Bonfils; di Folco; Udry; Santos; Lovis; Megevand et al. (2010). "Evidence against the young hot-Jupiter around BD +20 1790". arXiv:1003.3678 [astro-ph.EP].
  7. ^ Huelamo, N. et al.; Figueira, P.; Bonfils, X.; Santos, N. C.; Pepe, F.; Gillon, M.; Azevedo, R.; Barman, T.; Fernández, M.; Di Folco, E.; Guenther, E. W.; Lovis, C.; Melo, C. H. F.; Queloz, D.; Udry, S. (2008). "TW Hydrae: evidence of stellar spots instead of a Hot Jupiter". Astronomy and Astrophysics 489 (2): L9–L13. arXiv:0808.2386. Bibcode:2008A&A...489L...9H. doi:10.1051/0004-6361:200810596. Retrieved 2008-10-02. 

See also[edit]

Coordinates: Sky map 07h 23m 44s, +20° 24′ 51″