Kepler-1520

Kepler-1520 (initially published as KIC 12557548) is a K-type main-sequence star located in the constellation Cygnus. The star is particularly important, as measurements taken by the Kepler spacecraft indicate that the variations in the star's light curve cover a range from about 0.2% to 1.3% of the star's light being blocked.[2] This indicates that there may be a rapidly disintegrating planet, a prediction not yet conclusively confirmed, in orbit around the star, losing mass at a rate of 1 Earth mass every billion years.[2] The planet itself is about 0.1 Earth masses,[8] or just twice the mass of Mercury, and is expected to disintegrate in about 100[8]-200 million years.[2] The planet orbits its star in just 15.7 hours,[2] at a distance only two stellar diameters away from the star's surface,[9] and has an estimated effective temperature of about 2255 K.[8] The orbital period of the planet is one of the shortest ever detected in the history of the extrasolar planet search.[10] In 2016, the planet was confirmed as part of a data release by the Kepler spacecraft.

Kepler-1520
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 19h 23m 51.8899s[1]
Declination +51° 30′ 16.98″[1]
Apparent magnitude (V) 16.7[2]
Characteristics
Spectral type K4V[3]
Apparent magnitude (V) 16.7[2]
Apparent magnitude (J) 14.021±0.035[4]
Apparent magnitude (H) 13.433±0.035[4]
Apparent magnitude (K) 13.319±0.035[4]
Astrometry
Proper motion (μ) RA: 0.321±0.065[1] mas/yr
Dec.: 11.146±0.055[1] mas/yr
Parallax (π)1.6167 ± 0.0302[1] mas
Distance2,020 ± 40 ly
(620 ± 10 pc)
Absolute magnitude (MV)7.6[2]
Details
Mass0.76 ± 0.03[5] M☉
Radius0.71 ± 0.026[5] R☉
Luminosity0.14[2] L☉
Surface gravity (log g)4.610+0.018
−0.031[5] cgs
Temperature4677+82
−71[5] K
Metallicity [Fe/H]0.04 ± 0.15[5] dex
Rotation22.91±0.24 d[6]
Age4.47[5] Gyr
Other designations
Gaia DR2 2136216647412563840, KIC 12557548, 2MASS J19235189+5130170[7]
Database references
SIMBADdata
KICdata

Nomenclature and history

Prior to Kepler observation, Kepler-1520 had the 2MASS catalogue number 2MASS J19235189+5130170. In the Kepler Input Catalog it has the designation of KIC 12557548, and when it was found to have transiting planet candidates it was given the Kepler object of interest number of KOI-3794.

The star's planetary companion were discovered by NASA's Kepler Mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits move in front of their stars from the perspective of Earth. The name Kepler-1520 derives directly from the fact that the star is the catalogued 1,520th star discovered by Kepler to have confirmed planets.

The designation b, derive from the order of discovery. The designation of b is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet.[11] In the case of Kepler-1520, there was only one planet detected, so only the letter b is used.

Stellar characteristics

Kepler-1520 is a K-type star that is approximately 76% the mass of and 71% the radius of the Sun. It has a surface temperature of 4677 K and is about 4.47 billion years old.[5] In comparison, the Sun is about 4.6 billion years old[12] and has a surface temperature of 5778 K.[13]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 15. Therefore, it is too dim to be seen with the naked eye.

Planetary system

The planetary system of KIC 12557548 consists of one extrasolar planet, named Kepler-1520 b. This planet may possess a tail of dust and gas formed in a similar fashion to that of a comet[9] but, as opposed to the tail of a comet, containing molecules of pyroxene and aluminium(III) oxide. Based on the rate at which the particles in the tail are emitted, the mass of the planet has been constrained to less than 0.02 Earth masses — a higher-mass planet would have too much gravity to sustain the observed rate of mass loss.[14][2]

The Kepler-1520 planetary system[2][14] [15]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b <0.02 M⊕ 0.013 (1208425.494 miles) 0.6535538±0.0000001 ~0 — <1 (for albedo of 0.5) R⊕

Simulations show that the density of dust falls off rapidly with increasing distance from the planet.[2] Calculations conducted by Rappaport et al. show that the dust tail, in addition to absorbing light directly, may scatter some of the light which reaches it, contributing to a small apparent rise in stellar flux before the planet and its tail pass in front of the star, and a small apparent reduction in the stellar flux as the planet exits the plane of the stellar disk.[2]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Rappaport, S.; et al. (2012). "Possible Disintegrating Short-Period Super-Mercury Orbiting KIC 12557548". The Astrophysical Journal. 752 (1). 1. arXiv:1201.2662. Bibcode:2012ApJ...752....1R. doi:10.1088/0004-637X/752/1/1.
  3. "KIC 12557548 b". Retrieved 2 August 2016. Note: The EPE has not fully updated this data to be renamed Kepler-1520, but the spectral type is listed, hence this is the reference for it.
  4. Skrutskie, M. F.; et al. (2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode:2006AJ....131.1163S. doi:10.1086/498708.Vizier catalog entry
  5. "NASA Exoplanet Archive". NASA Exoplanet Science Institute. Retrieved 2016-08-02.
  6. Kawahara, Hajime; et al. (2013). "Starspots-Transit Depth Relation of the Evaporating Planet Candidate KIC 12557548b". The Astrophysical Journal Letters. 776 (1). L6. arXiv:1308.1585. Bibcode:2013ApJ...776L...6K. doi:10.1088/2041-8205/776/1/L6.
  7. "KOI-3794". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-08-19.
  8. Ouellette, Jennifer (May 26, 2012). "Dust to Dust: The Death of an Exoplanet". Discovery News. Discovery Communications, LLC. Retrieved June 9, 2012.
  9. Staff, Space.com (24 March 2012). "Possible Newfound Alien Planet is Falling to Pieces". Space.com. Retrieved June 9, 2012.
  10. "NASA's Kepler Detects Potential Evaporating Planet" (Press release). Jet Propulsion Laboratory. May 21, 2012. Retrieved June 11, 2012.
  11. Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  12. Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
  13. Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
  14. Perez-Becker, Daniel; Chiang, Eugene (2013). "Catastrophic evaporation of rocky planets". Monthly Notices of the Royal Astronomical Society. 433 (3): 2294–2309. arXiv:1302.2147. Bibcode:2013MNRAS.433.2294P. doi:10.1093/mnras/stt895.
  15. Van Werkhoven, T. I. M.; et al. (2014). "Analysis and interpretation of 15 quarters of Kepler data of the disintegrating planet KIC 12557548 b". Astronomy and Astrophysics. 561. A3. arXiv:1311.5688. Bibcode:2014A&A...561A...3V. doi:10.1051/0004-6361/201322398.
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