 This diagram compares our own solar system to Kepler-47, a double-star system containing two planets, one orbiting in the so-called "habitable zone." | |
| Discovery | |
|---|---|
| Discovered by | Kepler spacecraft |
| Discovery date | August 3, 2012[1] |
| Transit (Kepler Mission) | |
| Orbital characteristics | |
| 0.2962 (± 0.004)[2] AU | |
| Eccentricity | <0.035[2] |
| 49.532+0.04 −0.027[2] d | |
| Inclination | 89.70+0.5 −0.16[2] |
| Star | Kepler-47 (KOI-3154) |
| Physical characteristics | |
Mean radius | 3.03 (± 0.12)[2] R🜨 |
| Mass | 8.427 (± 0.62)[3] ME |
| Temperature | 449 K (176 °C; 349 °F) |
Kepler-47b (also known as Kepler-47 (AB) b and by its Kepler Object of Interest designation KOI-3154.01) is an exoplanet orbiting the binary star system Kepler-47, the innermost of three such planets discovered by NASA's Kepler spacecraft. The system, also involving two other exoplanets, is located about 3,400 light-years (1,060 parsecs) away.
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Kepler: Planet Occurence and the Habitable Zone -- Chris Burke (SETI Talks)
Transcription
Narrator: NASA's Kepler Mission has discovered the first system of multiple planets orbiting a pair of stars, or as astronomers call it, a circumbinary system. Located in the constellation of Cygnus, about 4,900 light-years from Earth, the discovery of Kepler-47 proves that more than one planet can form and persist while orbiting two stars. One star is similar to the sun in size but only 84 percent as bright. The second star is only one-third the size of the sun and less than one percent as bright. The inner planet, Kepler-47b, is the smallest known in orbit around two stars. The outer planet, Kepler-47c, is a gaseous giant, more than four times the size of Earth. Astrophysicists believe it might have an atmosphere blanketed with thick bright water clouds. It orbits its host stars every 303 days, placing it in the so-called "habitable zone." This is the region in a planetary system where liquid water could exist on the surface of an orbiting planet. While not a world thought to be hospitable for life, Kepler-47c is the first known circumbinary planet found in the habitable zone of its stars and it demonstrates the diversity of planetary systems in our galaxy. This discovery represents an important step for the Kepler mission in the effort to find Earth-size planets in the habitable zone of their host stars. (Electronic Sounds of Data) (Musical Tones)
Characteristics
Mass, radius and temperature
Kepler-47b is a gas giant, an exoplanet that is near the same mass and radius as the planets Jupiter and Saturn.[4] It has a temperature of 449 K (176 °C; 349 °F).[5] The planet has a radius of 3.03 R🜨, and is thought to have no solid surface.[6] It has a mass of 8.43 M🜨.
Host stars
The planet orbits in a circumbinary orbit around a (G-type) and (M-type) binary star system. The stars orbit each other about every 7.45 days.[2] The stars have masses of 1.04 M☉ and 0.35 M☉ and radii of 0.96 R☉ and 0.35 R☉, respectively.[2][1] They have temperatures of 5636 K and 3357 K.[2][1] Based on the stellar characteristics and orbital dynamics, an estimated age of 4–5 billion years for the system is possible. In comparison, the Sun is about 4.6 billion years old[7] and has a temperature of 5778 K.[8] The primary star is somewhat metal-poor, with a metallicity ([Fe/H]) of −0.25, or 56% of the solar amount.[1] The stars' luminosities (L☉) are 84% and 1% that of the Sun.[2][1]
The apparent magnitude of the system, or how bright it appears from Earth's perspective, is about 15.8. Therefore, it is too dim to be seen with the naked eye.
Orbit
Kepler-47b orbits around its parent stars every 45 days at a distance of 0.29 AU from its stars (close to where Mercury orbits from the Sun, which is about 0.39 AU).[9] It receives about 9.6 times as much sunlight that Earth does from the Sun.[5]
Discovery
Kepler-47b, as well as Kepler-47c, was first discovered by scientists, from both NASA and the Tel-Aviv University in Israel, using the Kepler space telescope.[10] Additionally, the planetary characteristics of both objects were identified by a team of astronomers at the University of Texas at Austin's McDonald observatory.[6] Both planets were discovered after transiting their parent stars, and they both seem to be orbiting along the same plane.[10]
Significance
Prior to the discovery of Kepler-47c, it was thought that binary stars with multiple planets could not exist. Gravitational issues caused by the parent stars would, it was believed, cause any circumbinary planets to either collide with each other, collide with one of the parent stars, or be flung out of orbit.[9] However, this discovery shows that multiple planets can form around binary stars, even in their habitable zones;[9] and while Kepler-47c is most likely unable to harbor life because it gas giant, other planets that could support life may orbit binary systems such as Kepler-47.[4]
See also
References
- ^ a b c d e Orosz, Jerome A.; Welsh, William F.; Carter, Joshua A.; Fabrycky, Daniel C.; Cochran, William D.; Endl, Michael; Ford, Eric B.; Haghighipour, Nader; MacQueen, Phillip J.; Mazeh, Tsevi; Sanchis-Ojeda, Roberto; Short, Donald R.; Torres, Guillermo; Agol, Eric; Buchhave, Lars A.; Doyle, Laurance R.; Isaacson, Howard; Lissauer, Jack J.; Marcy, Geoffrey W.; Shporer, Avi; Windmiller, Gur; Barclay, Thomas; Boss, Alan P.; Clarke, Bruce D.; Fortney, Jonathan; Geary, John C.; Holman, Matthew J.; Huber, Daniel; Jenkins, Jon M.; et al. (2012). "Kepler-47: A Transiting Circumbinary Multi-Planet System". Science. 337 (6101): 1511–4. arXiv:1208.5489v1. Bibcode:2012Sci...337.1511O. doi:10.1126/science.1228380. PMID 22933522. S2CID 44970411.
- ^ a b c d e f g h i "Kepler-47 b". NASA Exoplanet Archive. Retrieved August 5, 2016.
- ^ "Kepler-47". Exoplanets Data Explorer. Retrieved August 5, 2016.
- ^ a b "Newfound 'Tatooine' Alien Planet Bodes Well for E.T. Search". space.com. September 4, 2012. Retrieved January 5, 2013.
- ^ a b Kepler-47 (AB) hpcf.upr.edu
- ^ a b "Astronomers Find First Multi-Planet System Around a Binary Star". spacedaily.com. September 3, 2012. Retrieved January 5, 2013.
- ^ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
- ^ Fraser Cain (September 15, 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
- ^ a b c "Tatooine-like double-star systems can host planets". bbc.co.uk. August 29, 2012. Retrieved January 5, 2013.
- ^ a b "New worlds discovered, courtesy of US-Israel team". timesorisrael.com. August 30, 2012. Retrieved January 5, 2013.
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This page was last edited on 10 April 2024, at 08:45