Kepler-22b
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Kepler-22b (also known by its Kepler Object of Interest designation KOI-087.01) is an
Kepler-22b's radius is roughly twice that of Earth.
The planet's first
Physical characteristics
Mass, radius and temperature
Kepler-22b's radius was initially thought to be 2.4 times that of Earth, but has since been revised to 2.1 R🜨 as of 2023[update].[6][3] Its mass and surface composition remain unknown,[2][7] with only some rough estimates established: at the time of the discovery announcement, it was known to have fewer than 124 Earth masses at the 3-sigma confidence limit, and fewer than 36 Earth masses at 1-sigma confidence.[1] The adopted model in Kipping et al. (2013) does not reliably detect the mass (the upper limit is 52.8 ME).[8] As of 2023[update], the upper limit has been constrained to at most 9.1 ME.[3]
Kepler-22b, dubbed by scientists as a 'water world', might be an
In the absence of an atmosphere, its
Host star
The host star, Kepler-22, is a G-type star that is 3% less massive than the Sun and 2% smaller in volume. It has a surface temperature of 5,518 K (5,245 °C; 9,473 °F) compared with the Sun, which has a surface temperature of 5,778 K (5,505 °C; 9,941 °F).[13] The star is about 4 billion years old.[14] In comparison, the Sun is 4.6 billion years old.[15]
The apparent magnitude of Kepler-22 is 11.5, which means it is too dim to be seen with the naked eye.
Orbit
The only parameters of the planet's orbit that are currently available are its orbital period, which is about 290 days, and its inclination, which is approximately 90°. From Earth, the planet appears to make a transit across the disk of its host star.[16] In order to obtain further information about the details of the planet's orbit, other methods of planetary detection, such as the radial velocity method, need to be used. While such methods have been performed on the planet since its discovery, these methods have not yet detected an accurate value for the eccentricity of the planet and so (as of 2023) only an upper limit for the eccentricity of the planet has been set by astronomers.[3]
Habitability
The average distance from Kepler-22b to its host star
If Kepler-22b moves in a highly elliptical orbit, its surface temperature variance will be very high.
Climate
Scientists can estimate the possible surface conditions as follows:
- In the absence of an atmosphere, its
- If the atmosphere provides a greenhouse effect similar in magnitude to the one on Earth, it would have an average surface temperature of 295 K (22 °C).[17]
- If the atmosphere has a greenhouse effect similar in magnitude to the one on Venus, it would have an average surface temperature of 733 K (460 °C).
Recent estimates suggest that Kepler-22b has more than a 95% probability of being located in the empirical habitable zone defined by the recent Venus and early
Limits on satellites
The Hunt for Exomoons with Kepler (HEK) project has studied the Kepler photometry of the planet, to find any evidence of transit timing and duration variations that may be caused by an orbiting satellite. Such variations were not found, so ruling out the existence of any satellites of Kepler-22b with a mass greater than 0.54 Earth masses.[8]
Discovery and observation
The planet's first transit in front of its host star was observed on Kepler's third day of scientific operations, on 12 May 2009.[18] The third transit was detected on 15 December 2010. Additional confirmation data was provided by the Spitzer Space Telescope and ground-based observations. Confirmation of the existence of Kepler-22b was announced on 5 December 2011.[7]
Past transit dates
Transits of Kepler-22b | |||||
---|---|---|---|---|---|
Date(s) of transit[1] |
Time ( UTC )
|
Notes | |||
Start | Mid | End | |||
15 May 2009 | First observed transit by Kepler space telescope | ||||
1 March 2010 | Observed by Spitzer[19] | ||||
15 December 2010 | 3rd transit observed by Kepler | ||||
1 October 2011 | 7.4 hour transit observed by Spitzer space telescope, confirming the planet |
See also
References
- ^ S2CID 50813889. The article gives Julian dates, which are converted at imcce.fr Archived 22 October 2011 at the Wayback Machine(all dates in Univ. Time)
- ^ a b "NASA – NASA's Kepler Confirms Its First Planet in Habitable Zone of Sun-like Star". NASA Press Release. Retrieved 6 December 2011.
- ^ S2CID 258078829.
- ^ Dunbar, Brian (5 December 2011). "NASA's Kepler Mission Confirms Its First Planet in Habitable Zone of Sun-like Star". NASA. Retrieved 7 January 2022.
- ^ Brennan, Pat (n.d.). "Kepler-22b". Exoplanet Exploration: Planets Beyond our Solar System. NASA. Retrieved 23 November 2020.
- ^ "Kepler-22 b". NASA Exoplanet Archive. Retrieved 4 July 2016.
- ^ a b c "Kepler 22-b: Earth-like planet confirmed". BBC Online. 5 December 2011. Retrieved 6 December 2011.
- ^ S2CID 119256408.
- ^ Scharf, Caleb A. (8 December 2011). "You Can't Always Tell An Exoplanet By Its Size". Scientific American. Retrieved 5 April 2024.: "If it [Kepler-22b] had a similar composition to the Earth, then we’re looking at a world in excess of about 40 Earth masses".
- ^ Angus, Ruth (31 July 2014). "Most 1.6 Earth-radius planets are not rocky". Astrobites.
- ^ Rincon, Paul (5 December 2011). "A home from home: Five planets that could host life". BBC News. Retrieved 26 November 2016.
- Discovery News. Archived from the originalon 30 August 2012. Retrieved 9 November 2020.
- ^ Cain, Fraser (15 September 2008). "Temperature of the Sun". Universe Today. Archived from the original on 29 August 2010. Retrieved 19 February 2011.
- S2CID 20205600.
- ^ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
- ^ a b "Notes for-22 b". Extrasolar Planets Encyclopaedia. Retrieved 6 December 2011.
- ^ "NASA Telescope Confirms Alien Planet in Habitable Zone". Space.com. 12 May 2011
- Dr. Tony Phillips (5 December 2011). "Kepler Confirms First Planet in Habitable Zone of Sun-like Star". NASA science news. Retrieved 31 January 2012.
The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season.
- ^ NASA (7 June 2013). "NASA's Kepler Mission Confirms Its First Planet in Habitable Zone of Sun-like Star". NASA. Retrieved 19 April 2018.
External links
- "NASA's Kepler Confirms Its First Planet In Habitable Zone" Archived 5 May 2012 at the Wayback Machine (NASA)
- "Kepler discoveries: Kepler-22b: 'a yearly orbit of 289 days'" (NASA)
- "View of Kepler 22-b Sky Location" (Worldwide Telescope)
- Kepler-22b – First Discovered Planet In Habitable Zone on YouTube
- Kepler 22b – a planet in a star's habitable zone on YouTube
- Kepler mission newsfeed