Astronomy:Kepler-93b

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Kepler-93b
An artist's impression comparing the size and internal structure of Earth (left) and Kepler-93b (right).
Discovery[1]
Discovered byGeoffrey W. Marcy et al.
Discovery dateFebruary 2014 (announced)
Transit method
Designations
KIC 3544595 b, KOI-69.01, BD+38 3583b, TYC 3134-218-1 b[2]
Orbital characteristics[3]
0.05343±0.00065 astronomical unit|AU
Eccentricity0
Orbital period4.72673978(97) d
Inclination89.183°±0.044°
Semi-amplitude1.89±0.21 m/s
StarKepler-93
Physical characteristics[3]
Mean radius1.478±0.019 R🜨
Mass4.66±0.53 M🜨
Mean density7.93+0.96
−0.94 g/cm3
Physics1133±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)[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]

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/cm3[9] thanks to its high mass of roughly 4 M⊕, 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⊕, 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 |♃|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 MJ 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 MJ, 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. ↑ 1.0 1.1 1.2 1.3 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. doi:10.1088/0067-0049/210/2/20. Bibcode: 2014ApJS..210...20M. 
  2. ↑ "The Extrasolar Planet Encyclopaedia — Kepler-93b". Extrasolar Planets Encyclopaedia. https://exoplanet.eu/catalog/kepler_93_b--2275/. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Bonomo, A. S. 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. doi:10.1051/0004-6361/202346211. Bibcode: 2023A&A...677A..33B. 
  4. ↑ Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  5. ↑ 5.0 5.1 5.2 "BD+38 3853". SIMBAD. https://simbad.u-strasbg.fr/simbad/sim-id?Ident=+BD%2B38+3583. 
  6. ↑ "SKY-MAP.ORG - Interactive Sky Map". Sky-Map.org. http://www.sky-map.org/. 
  7. ↑ 7.0 7.1 "Gauging an Alien World's Size". NASA. 2014-07-22. https://www.nasa.gov/image-article/gauging-an-alien-worlds-size/. 
  8. ↑ 8.0 8.1 8.2 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). doi:10.1088/0004-637X/790/1/12. 12. Bibcode: 2014ApJ...790...12B. 
  9. ↑ 9.0 9.1 9.2 9.3 Dressing, Courtney D. et al. (February 2015). "The Mass of Kepler-93b and The Composition of Terrestrial Planets". The Astrophysical Journal 800 (2). doi:10.1088/0004-637X/800/2/135. 135. Bibcode: 2015ApJ...800..135D. 
  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. ↑ 11.0 11.1 Li, Zeng et al. (March 2016). "Mass-Radius Relation for Rocky Planets based on PREM". The Astrophysical Journal 819 (2). doi:10.3847/0004-637X/819/2/127. 127. Bibcode: 2016ApJ...819..127Z. 
  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. https://periodictable.com/Elements/013/data.html. 
  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. doi:10.1126/science.1226919. PMID 23118187. Bibcode: 2012Sci...338..651C. (registration required)
  15. ↑ Williams, D.R. (1 July 2013). "Sun Fact Sheet". NASA Goddard Space Flight Center. http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html. 
  16. ↑ John E. Bortle (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. http://www.skyandtelescope.com/resources/darksky/3304011.html. 



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