Astronomy:K2-155d

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K2-155d
Discovery
Discovered byTeruyuki Hirano et al. [1]
Discovery siteTokyo Institute of Technology
Discovery dateMarch 2018
Transit method
Designations
LP 415-17 c, EPIC 210897587 c[2]
Orbital characteristics
0.1886 (± 0.0066)[3] AU
Eccentricityunknown
Orbital period40.6835 (± 0.0031)[3] d
Inclinationunknown
StarK2-155
Physical characteristics
Mean radius1.64 +0.18−0.17[3] R⊕
Mean density5.41±1.11 g/cm3
Physics289 K (16 °C; 61 °F)[4]


K2-155d is a potentially habitable Super-Earth exoplanet in the K2-155 system.[5] It is the outermost of three known planets orbiting around the K-type star K2-155 in the constellation Taurus, approximately 290 light years (90 parsecs) from Earth.[6] It is one of 15 new exoplanets around red dwarf stars discovered by Japanese astronomer Teruyuki Hirano of the Tokyo Institute of Technology and his team.[1] The team used data from NASA's Kepler Space Telescope during its extended K2 "Second Light" mission. K2-155d orbits near the so-called habitable zone of its system, and has the potential to host liquid water.[7][5]

Discovery and observations

K2-155d is one of 15 exoplanets discovered by a team of Japanese astronomers led by Teruyuki Hirano at the Tokyo Institute of Technology.[5] Its discovery is based on data from the K2 mission of NASA's Kepler spacecraft.[5] The exoplanet has also been observed from ground-based telescopes including the Nordic Optical Telescope (NOT) in La Palma and the Subaru Telescope in Hawaii.[5] Its characteristics were confirmed using speckle imaging and high-dispersion optical spectroscopy.[3] The mass of K2-155d and the brightness of its host star may be measured by future observations from the W. M. Keck Observatory and the James Webb Space Telescope.[3] The brightness of its host star makes K2-155d a good target for future studies using instruments such as the James Webb Space Telescope.[3]

Characteristics

K2-155d is a super-Earth exoplanet with a radius 1.64 times that of Earth, near the transition zone between small rock-based and larger gaseous planets.[8][3][7] Climate models predict that it is located near its star's habitable zone and has an insolation 1.67 ± 0.38 (between 1.29 and 2.05) times that of Earth.[3] Its physical temperature is estimated to be 289 K (16 degrees Celsius or 61 degrees Fahrenheit).[4] Studies have shown that the planet would maintain a moderate surface temperature if its insolation is smaller than ~1.5 times that of Earth.[3]

K2-155d is one of three known planets in the system orbiting K2-155, a red dwarf star located 62.3 parsecs (203 ly) from Earth.[3] Its parent star has 88% less volume than the Sun.[9] K2-155d orbits its star with a 40.7 day period, but as the planet is tidally locked the same side always faces its sun.[5] K2-155d has an orbital radius of 0.1886 AU[8] and studies suggest that the planet has a low orbital eccentricity.[10]

Potential habitability

K2-155d has been labeled a potentially habitable planet that may be able to harbor liquid water.[7][5] A three-dimensional climate simulation was used to confirm the possibility of the existence of water.[5] However, its discoverer Teruyuki Hirano was cautious about the findings, stating that they do not guarantee K2-155d is habitable, as the ranges in its orbit and temperature allow the possibility of it being outside the habitable zone.[7] Factors such as the absence of solar flares could also decide if K2-155d is habitable.[5]

Size comparison of the planet K2-155 d (artistic concept) with Earth

References

  1. ↑ 1.0 1.1 "15 new planets confirmed around cool dwarf stars". Tokyo Tech News. March 12, 2018. https://www.titech.ac.jp/english/news/2018/040761.html. 
  2. ↑ "The Extrasolar Planet Encyclopaedia — K2-155 d". Extrasolar Planets Encyclopaedia. https://exoplanet.eu/catalog/k2_155_d--6709/. Retrieved 2024-04-29. 
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 Hirano, Teruyuki et al. (March 2018). "K2-155: A Bright Metal-poor M Dwarf with Three Transiting Super-Earths". The Astronomical Journal 155 (3): 11. doi:10.3847/1538-3881/aaaa6e. 124. Bibcode: 2018AJ....155..124H. 
  4. ↑ 4.0 4.1 "HEC: Exoplanets Calculator (K2-155d)". Planetary Habibility Laboratory. http://phl.upr.edu/projects/habitable-exoplanets-catalog/calculators. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Mack, Eric (March 13, 2018). "A super-Earth around a red star could be wet and wild". https://www.cnet.com/news/super-earth-exoplanet-k2-155d-found-could-be-habitable-nasa/. 
  6. ↑ "K2-155 PLANET HOST OVERVIEW PAGE". NASA Exoplanet Archive. https://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=K2-155. 
  7. ↑ 7.0 7.1 7.2 7.3 Dovey, Dana (March 14, 2018). "Super Earth 200 Light-Years Away May Hold Ideal Temperatures For Liquid Water And Life". Newsweek. http://www.newsweek.com/space-exoplanet-dwarf-star-k2-155d-843565. 
  8. ↑ 8.0 8.1 "Confirmed Planet Overview Page: K2-155d". NASA Exoplanet Archive. 2018. https://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=K2-155+d&type=CONFIRMED_PLANET. 
  9. ↑ "K2-155d". Exoplanet Data Explorer. 2018. http://exoplorer.org/en/exoplanets/k2-155-d. 
  10. ↑ Eylen, Vincent; Albrecht, Simon (May 11, 2015). "Eccentricity from transit photometry: small planets in Kepler multi-planet systems have low eccentricities". The Astrophysical Journal 808 (2): 126. doi:10.1088/0004-637X/808/2/126. Bibcode: 2015ApJ...808..126V. 



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