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Kepler-93b

An artist's impression comparing the size and internal structure of Earth (left) and Kepler-93b (right).
Discovery
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
Orbital characteristics
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
Mean radius	1.478±0.019 R🜨
Mass	4.66±0.53 M🜨
Mean density	7.93+0.96 −0.94 g/cm
Temperature	1133±17 K (860 °C; 1,580 °F, equilibrium)

Kepler-93b (KOI-69b) is a hot, dense transiting Super-Earth exoplanet located approximately 313 light-years (96 parsecs) away in the constellation of Lyra, orbiting the G-type star Kepler-93. Its discovery was announced in February 2014 by American astronomer Geoffrey Marcy and his team. 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.

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), making it the most precisely measured exoplanet ever in terms of radius as of July 2014. The planet is substantially denser than Earth at 6.88±1.18 g/cm thanks to its high mass of roughly 4 M_E, consistent with a rocky composition of iron and magnesium silicate. In 2023, the planet's mass was revised upward to 4.66±0.53 M_E, placing its density at 7.93
_−0.94 g/cm, roughly the same as the metal iron (7.874 g/cm).

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%), compared to the 32.5 ± 0.1% of Earth and 31 ± 1% of Venus.

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

Host star

The planet orbits a Sun-like (spectral type G5V) 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. In comparison, the Sun is 4.6 billion years old, has a temperature of 5,772 K (5,499 °C; 9,930 °F) and a spectral type of G2V. The apparent magnitude of the star is 9.931, making it too dim to be visible from Earth by the naked eye.

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. 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), 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, 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.

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); aluminium melts at 660.32 °C (933.47 K; 1,220.58 °F).

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.

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