GSC 03549-02811 (sometimes referred to as Kepler-1, or either TrES-2A or TrES-2 parent star in reference to its exoplanet TrES-2b)[7] is a binary star system containing a G-type main-sequence star similar to the Sun. This star is located approximately 704 light-years away in the constellation of Draco. The apparent magnitude of this star is 11.41, which means it is not visible to the naked eye but can be seen with a medium-sized amateur telescope on a clear dark night. The age of this star is about 5 billion years.[4]
Nomenclature
The designation GSC 03549-02811 comes from the Guide Star Catalog.
The star is often called TrES-2,[8] in reference to its planet discovered by the Trans-Atlantic Exoplanet Survey (TrES). The discovery paper[2] and the SIMBAD database[4] use this designation for the planet itself, but other sources call the star TrES-2 (or TrES-2A)[9] and the planet TrES-2b,[10] following the standard exoplanet naming convention. In keeping with the planet being component b, the companion star is designated TrES-2C, although it is also designated Kepler-1B.[4]
The planet was also observed by the Kepler space telescope, and so the star is also known as Kepler-1.[4] Since the planet transits the star, the star is classified as a planetary transit variable and has received the variable star designation V581 Draconis.[11]
Binary star
In 2008 a study was undertaken of fourteen stars with exoplanets that were originally discovered using the transit method through relatively small telescopes. These systems were re-examined with the 2.2M reflector telescope at the Calar Alto Observatory in Spain. This star system, along with two others, was determined to be a previously unknown binary star system. The previously unknown secondary star is a dim magnitude 15 K-type star separated by about 232 AU from the primary, appearing offset from the primary by about one arc second in the images. This discovery resulted in a significant recalculation of parameters for both the planet and the primary star.[3]
Planetary system

In 2006, the exoplanet TrES-2b was discovered by the Trans-Atlantic Exoplanet Survey using the transit method. It was also within the field of view of the Kepler Mission planet-hunter spacecraft.[2] This system continues to be studied by other projects and the parameters are continuously improved.[13] The planet orbits the primary star.[3]
TrES-2b is a hot Jupiter, with a mass and size similar to those of Jupiter but an orbital period of only two days. Its orbit is prograde relative to its star's rotation.[10] In 2011, TrES-2b was found to have a very low albedo, reflecting less than 1 percent of the light from its star, making it the darkest known exoplanet at the time. However, it also emits a significant amount of light because its surface temperature is so hot that it glows red.[14] Due to its close orbit, it is assumed to be tidally locked to its parent star.[15]
Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | 1.199(52) MJ | 0.03555(75) | 2.4706133738(187) | 0 (assumed) | 83.908(9)° | 1.189(25) RJ |
The Kepler mission

In March 2009, NASA launched the Kepler spacecraft. This spacecraft was a dedicated mission to discover extrasolar planets by the transit method from solar orbit. In April 2009 the project released the first light images from the spacecraft, and TrES-2b was one of two objects highlighted in these images. Although TrES-2b was not the only known exoplanet in the field of view of this spacecraft, it was the only one identified in the first-light images. This object was important for calibration and check-out.[17]
See also
References
- ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c d e O'Donovan, Francis T.; et al. (2006). "TrES-2: The First Transiting Planet in the Kepler Field". The Astrophysical Journal Letters. 651 (1): L61 – L64. arXiv:astro-ph/0609335. Bibcode:2006ApJ...651L..61O. doi:10.1086/509123.
- ^ a b c d e f g h i j k Daemgen, S.; et al. (2009). "Binarity of transit host stars. Implications for planetary parameters". Astronomy and Astrophysics. 498 (2): 567–574. arXiv:0902.2179. Bibcode:2009A&A...498..567D. doi:10.1051/0004-6361/200810988. S2CID 9893376.
- ^ a b c d e f g "Kepler-1". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2009-04-22.
- ^ a b c Skrutskie, Michael F.; et al. (1 February 2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode:2006AJ....131.1163S. doi:10.1086/498708. Vizier catalog entry
- ^ Bonomo, A. S.; Desidera, S.; et al. (June 2017). "The GAPS Programme with HARPS-N at TNG. XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets". Astronomy & Astrophysics. 602: A107. arXiv:1704.00373. Bibcode:2017A&A...602A.107B. doi:10.1051/0004-6361/201629882.
- ^ Mislis, D.; Schröter, S.; Schmitt, J. H. M. M.; Cordes, O.; Reif, K. (February 2010). "Multi-band transit observations of the TrES-2b exoplanet". Astronomy and Astrophysics. 510: A107. arXiv:0912.4428. Bibcode:2010A&A...510A.107M. doi:10.1051/0004-6361/200912910.
- ^ "TrES-2 Overview". NASA Exoplanet Archive. Retrieved 10 March 2025.
- ^ Barclay, Thomas; Huber, Daniel; et al. (December 2012). "Photometrically Derived Masses and Radii of the Planet and Star in the TrES-2 System". The Astrophysical Journal. 761 (1): 53. arXiv:1210.4592. Bibcode:2012ApJ...761...53B. doi:10.1088/0004-637X/761/1/53.
- ^ a b Winn, Joshua N.; Johnson, John Asher; et al. (August 2008). "The Prograde Orbit of Exoplanet TrES-2b". The Astrophysical Journal. 682 (2): 1283–1288. arXiv:0804.2259. Bibcode:2008ApJ...682.1283W. doi:10.1086/589235.
- ^ "V581 Dra". General Catalog of Variable Stars - VizieR. Retrieved 10 March 2025.
- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 12 March 2025.
- ^ Alessandro Sozzetti; Torres, Guillermo; Charbonneau, David; Latham, David W.; Holman, Matthew J.; Winn, Joshua N.; Laird, John B.; o’Donovan, Francis T. (August 1, 2007). "Improving Stellar and Planetary Parameters of Transiting Planet Systems: The Case of TrES-2". The Astrophysical Journal. 664 (2): 1190–1198. arXiv:0704.2938. Bibcode:2007ApJ...664.1190S. doi:10.1086/519214. S2CID 17078552.
- ^ Kipping, David M.; Spiegel, David S. (October 2011). "Detection of visible light from the darkest world". Monthly Notices of the Royal Astronomical Society: Letters. 417 (1): L88 – L92. arXiv:1108.2297. Bibcode:2011MNRAS.417L..88K. doi:10.1111/j.1745-3933.2011.01127.x.
- ^ "Coal-Black Alien Planet is Darkest Ever Seen". 11 August 2011.
- ^ Raetz, St.; et al. (2014). "Transit timing of TrES-2: A combined analysis of ground- and space-based photometry". Monthly Notices of the Royal Astronomical Society. 444 (2): 1351–1368. arXiv:1408.7022. Bibcode:2014MNRAS.444.1351R. doi:10.1093/mnras/stu1505.
- ^ "Kepler Eyes Cluster and Known Planet". NASA. 2009-04-16. Retrieved 2009-05-09.
External links
- "Host to 'Hot Jupiter' (labeled)". multimedia/images. NASA. 2009-04-16. Retrieved 2009-04-28.
- "TrES-2". Exoplanets. Archived from the original on 2009-11-25. Retrieved 2009-04-28.
- KIC 11446443
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