Kepler-296e[1][2][3]
Planet K2-18 b and star (left), where picture can be equated to Kepler-296f (foreground), e (small planet in center) and star (left).
Discovery
Discovery siteKepler Space Observatory
Discovery date2014
Transit
Orbital characteristics
0.17400 AU (26,030,000 km)
Eccentricity<0.33[4]
34.14234700 d
Inclination89.950
StarKepler-296
Physical characteristics
Mean radius
1.530 R🜨 [4]
Mass4.51276 M🜨[5]
Temperature267 K (−6 Â°C; 21 Â°F)

    Kepler-296e (also known by its Kepler Object of Interest designation KOI-1422.05) is a confirmed super-Earth exoplanet orbiting within the habitable zone of Kepler-296. The planet was discovered by NASA's Kepler spacecraft using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. NASA announced the discovery of the exoplanet on 26 February 2014.[1]

    Characteristics

    Kepler-296e was assumed to be a super-Earth with a radius 1.75 times that of Earth. A more revised estimate puts the planet at 1.53 Earth-radii. The planet orbits Kepler-296 once every 34.1 days at a semimajor axis distance of 0.169 AU.[4] It would have a mass of 4.51276 Earth masses, with the higher-than-Earth density suggested by exoplanetkyoto.[6] With an Earth-like density, the mass would be 3.581577 Earth masses. The planet's equilibrium temperature is 267 K (–6 °C; 21 °F), much higher than that of Earth.

    Habitability

    The planet was announced as being located within the habitable zone of Kepler-296. In this region, liquid water could exist on the surface of the planet.[7] It is likely rocky, with its relatively low radius, in contrast to f, which is larger.[4][7] As of 2017, with an ESI of 0.85, it is the fifth-most Earth-like planet after Kepler-438b, TRAPPIST-1 d, and two Gliese-designated planets, GJ 3323 b and GJ 273 b, which were both discovered in 2017.[8] The planet receives 1.4 times the Earth's solar flux, putting it well within the habitable zone and just barely beyond the runaway G line.[8][9] According to Kopparapu et. al (2013), the planet is within the most conservative boundaries of the habitable zone.[10] However, it has an eccentric orbit,[4][11] with a maximum eccentricity of 0.33 to a confidence of 3-sigma.[4] The planet's equilibrium temperature varies depending on its albedo: for a non-tidally locked planet with an Earth-like albedo of 0.3, it is 234 K (–39 °C; –38 °F), and for a Venus-like albedo of 0.7, it is 189 K (–84 °C; -119 °F). For a tidally locked planet with an Earth-like albedo of 0.3, the equilibrium temperature is 278 K (5 °C; 41 °F).[6]

    Tidal locking

    According to [12], an Earth-size planet with eccentricity <0.1, no moons, and no obliquity orbiting at the Earth boundary within the habitable zone is tidally locked around a star with a mass of <0.42 solar masses (~M2 or later). When the Solar System is used as a yardstick, then the limit is 0.72 solar masses (~K3-4 or later). However, the orbit of planet e, is likely more eccentric than the modeled fictional planet, so the planet may not have had enough time to tidally lock.[4][11]

    See also

    References

    1. 1 2 Staff (26 February 2014). "715 Newly Verified Planets More Than Triples the Number of konfirmed Kepler Planets". NASA. Archived from the original on 4 March 2014. Retrieved 8 January 2015.
    2. ↑ Lissauer, Jack J.; et al. (25 February 2014). "Validation of Kepler's Multiple Planet Candidates. II: Refined Statistical Framework and Descriptions of Systems of Special Interest". The Astrophysical Journal. 784 (1): 44. arXiv:1402.6352. Bibcode:2014ApJ...784...44L. doi:10.1088/0004-637X/784/1/44. S2CID 119108651.
    3. ↑ Rowe, Jason F. (2014). "Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems". The Astrophysical Journal. 784 (1): 45. arXiv:1402.6534. Bibcode:2014ApJ...784...45R. doi:10.1088/0004-637X/784/1/45. S2CID 119118620.
    4. 1 2 3 4 5 6 7 content
    5. ↑ content
    6. 1 2 "Kepler-296 e". www.exoplanetkyoto.org. Retrieved 27 November 2023.
    7. 1 2 "New Study Reassesses Habitability of Exoplanets Around Multiple Star Systems - AmericaSpace". www.americaspace.com. 25 May 2015. Retrieved 27 November 2023.
    8. 1 2 "PHL @ UPR Arecibo – the Habitable Exoplanets Catalog". Archived from the original on 10 February 2022. Retrieved 20 March 2022.
    9. ↑ "The Five Planets in the Kepler-296 Binary System All Orbit the Primary: A Statistical and Analytical Analysis". IPAC. Retrieved 27 November 2023.
    10. ↑ "Kepler-296 e". www.exoplanetkyoto.org. Retrieved 27 November 2023.
    11. 1 2 Huffman, Darrell. "Gravity Simulator | Kepler-296 - System With 5 Exoplanets". gravitysimulator.org. Retrieved 27 November 2023.
    12. ↑ Barnes, Rory (1 December 2017). "Tidal locking of habitable exoplanets". Celestial Mechanics and Dynamical Astronomy. 129 (4): 509–536. doi:10.1007/s10569-017-9783-7. ISSN 1572-9478.
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