Kepler-93b

Kepler-93b (KOI-69b) is a hot, dense transiting Super-Earth exoplanet located approximately 313 light-years (96 parsecs)^[4] away in the constellation of Lyra,^[5][6] orbiting the G-type star^[5] Kepler-93. Its discovery was announced in February 2014 by American astronomer Geoffrey Marcy and his team.^[1] In July 2014, its radius was determined with a mere 1.3% margin of error, the most precise measurement ever made for an exoplanet's radius at the time.^[7]

Kepler-93b

An artist's impression comparing the size and internal structure of Earth (left) and Kepler-93b (right).
Discovery[1]
Discovered by	Geoffrey W. Marcy et al.
Discovery date	February 2014 (announced)
Detection method	Transit method
Designations
Alternative names	KIC 3544595 b, KOI-69.01, BD+38 3583b, TYC 3134-218-1 b[2]
Orbital characteristics[3]
Semi-major axis	0.05343±0.00065 AU
Eccentricity	0
Orbital period (sidereal)	4.72673978(97) d
Inclination	89.183°±0.044°
Semi-amplitude	1.89±0.21 m/s
Star	Kepler-93
Physical characteristics[3]
Mean radius	1.478±0.019 R🜨
Mass	4.66±0.53 M🜨
Mean density	7.93+0.96 −0.94 g/cm3
Temperature	1133±17 K (860 °C; 1,580 °F, equilibrium)

Physical properties

The planet has a radius of around 1.478 R_🜨 (9,416 km), with an uncertainty of just 0.019 R_🜨 (121 km),^[8] making it the most precisely measured exoplanet ever in terms of radius as of July 2014.^[7] The planet is substantially denser than Earth at 6.88±1.18 g/cm^3[9] thanks to its high mass of roughly 4 M_E, consistent with a rocky composition of iron and magnesium silicate.^[9] In 2023, the planet's mass was revised upward to 4.66±0.53 M_E, placing its density at 7.93^+0.96
_−0.94 g/cm³,^[3] roughly the same as the metal iron (7.874 g/cm³).^[10]

Based on these findings, the interior of the planet is likely similar to that of Earth and Venus, with an iron core making up around 26% of its total mass (albeit with a large uncertainty of ±20%),^[11] compared to the 32.5 ± 0.1% of Earth and 31 ± 1% of Venus.^[11]

The planet orbits its host star every 4.73 days^[8] at a distance of 0.05343 AU (7,993,000 km),^[3] less than one-seventh the radius of Mercury's orbit. Its equilibrium temperature is approximately 1,133 K (860 °C; 1,580 °F),^[3] which is as hot as lava and well above the melting point of aluminium.^{[lower-alpha 1]}

Host star

The planet orbits a Sun-like (spectral type G5V)^[5] star named Kepler-93. The star has a mass of 0.911 M_☉ and a radius of 0.919 R_☉. It has a temperature of 5,669 K (5,396 °C; 9,745 °F) and is 6.6 billion years old.^[8] In comparison, the Sun is 4.6 billion years old,^[14] has a temperature of 5,772 K (5,499 °C; 9,930 °F) and a spectral type of G2V.^[15] The apparent magnitude of the star is 9.931,^[9] making it too dim to be visible from Earth by the naked eye.^[16]

The star is host to an additional non-transiting confirmed companion, Kepler-93c, which was discovered using the radial-velocity method and announced in 2014, concurrently with Kepler-93b.^[1] The object is most likely a brown dwarf orbiting much farther out than Kepler-93b, though its precise nature remains uncertain. The discovery paper reported a lower limit on the mass of 3 M_J and a minimal orbital period of 1,460 days (4.0 years),^[1] while a subsequent study in 2015 weighed the planet at >8.5 M_J and presented an orbital period of >10 years, placing its orbit beyond 4.5 AU from the star,^[9] and a 2023 study increased these lower limits further, to a mass >21 M_J, an orbital period >48.6 years, and a semi-major axis >13 AU.^[3]

See also

• List of exoplanets discovered by the Kepler space telescope
• List of transiting exoplanets
• Other dense super-Earths orbiting close to their parent stars:
  • CoRoT-7b, has a similar radius to Kepler-93b, but is more massive and much hotter.
  • HD 219134 b, has a similar radius, mass and temperature.
  • Kepler-10b, has a similar radius, but is slightly less massive and much hotter.
  • Kepler-36b, has a similar radius, mass and temperature.

Footnotes

1. The temperature of lava is typically at 800–1,200 °C (1,070–1,470 K; 1,470–2,190 °F);^[12] aluminium melts at 660.32 °C (933.47 K; 1,220.58 °F).^[13]

References

1. Marcy, Geoffrey W.; et al. (February 2014). "Masses, Radii, and Orbits of Small Kepler Planets: The Transition from Gaseous to Rocky Planets". The Astrophysical Journal Supplement Series. 210 (2): 20. arXiv:1401.4195. Bibcode:2014ApJS..210...20M. doi:10.1088/0067-0049/210/2/20. hdl:1721.1/92945. S2CID 10760418.
2. "The Extrasolar Planet Encyclopaedia — Kepler-93b". Extrasolar Planets Encyclopaedia. Retrieved 2024-05-04.
3. Bonomo, A. S.; Dumusque, X.; et al. (September 2023). "Cold Jupiters and improved masses in 38 Kepler and K2 small planet systems from 3661 HARPS-N radial velocities. No excess of cold Jupiters in small planet systems". Astronomy & Astrophysics. 677: A33. arXiv:2304.05773. Bibcode:2023A&A...677A..33B. doi:10.1051/0004-6361/202346211. S2CID 258078829.
4. 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.
5. "BD+38 3853". SIMBAD. Retrieved 2024-05-08.
6. "SKY-MAP.ORG - Interactive Sky Map". Sky-Map.org. Retrieved 2024-05-08.
7. "Gauging an Alien World's Size". NASA. 2014-07-22. Retrieved 2024-05-07.
8. Ballard, Sarah; et al. (July 2014). "Kepler-93b: A Terrestrial World Measured to within 120 km, and a Test Case for a New Spitzer Observing Mode". The Astrophysical Journal. 790 (1). arXiv:1405.3659. Bibcode:2014ApJ...790...12B. doi:10.1088/0004-637X/790/1/12. S2CID 12644226. 12.
9. Dressing, Courtney D.; et al. (February 2015). "The Mass of Kepler-93b and The Composition of Terrestrial Planets". The Astrophysical Journal. 800 (2). arXiv:1412.8687. Bibcode:2015ApJ...800..135D. doi:10.1088/0004-637X/800/2/135. S2CID 53471038. 135.
10. Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
11. Li, Zeng; et al. (March 2016). "Mass-Radius Relation for Rocky Planets based on PREM". The Astrophysical Journal. 819 (2). arXiv:1512.08827. Bibcode:2016ApJ...819..127Z. doi:10.3847/0004-637X/819/2/127. S2CID 119111854. 127.
12. Philpotts, Anthony R.; Ague, Jay J. (2009). Principles of igneous and metamorphic petrology (2nd ed.). Cambridge, UK: Cambridge University Press. pp. 53–55. ISBN 9780521880060.
13. "Technical data for the element Aluminum in the Periodic Table". The Photographic Periodic Table of the Elements. Retrieved 2024-05-31.
14. Connelly, JN; Bizzarro, M; Krot, AN; Nordlund, Å; Wielandt, D; Ivanova, MA (2 November 2012). "The Absolute Chronology and Thermal Processing of Solids in the Solar Protoplanetary Disk". Science. 338 (6107): 651–655. Bibcode:2012Sci...338..651C. doi:10.1126/science.1226919. PMID 23118187. S2CID 21965292.(registration required)
15. Williams, D.R. (1 July 2013). "Sun Fact Sheet". NASA Goddard Space Flight Center. Archived from the original on 2010-07-15. Retrieved 2013-08-12.
16. John E. Bortle (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Archived from the original on 2009-03-23. Retrieved 2009-11-18.