KIC 12557548

KIC 12557548

Artist's concept of the unconfirmed extrasolar planet KIC 12557548 b orbiting its host star. The planet is rapidly losing mass through the sublimation of its planetary surface and has a tail of dust.
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 19h 23m 51.891s[1]
Declination +51° 30′ 17.00″[1]
Apparent magnitude (V) 16.7[2]
Characteristics
Spectral type K4V—K7V[2]
Apparent magnitude (V) 16.7[2]
Apparent magnitude (J) 14.02[1]
Apparent magnitude (H) 13.43[1]
Apparent magnitude (K) 13.32[1]
Astrometry
Distance1500 ± ly
(470 ± pc)
Absolute magnitude (MV)7.6[2]
Details
Mass0.70+0.08-0.04[2] M☉
Radius0.7[note 1] R☉
Luminosity0.14[2] L☉
Temperature4300 ± 250[2] K
Age≥ 0.2[2] Gyr
Other designations
2MASS J19235189+5130170[1]

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,[3] or just twice the mass of Mercury, and is expected to disintegrate in about 100[3]-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,[4] and has an estimated effective temperature of about 2255 K.[3] The orbital period of the planet is one of the shortest ever detected in the history of the extrasolar planet search.[5]

History of detection

The existence of the planet was first evidenced in data collected by the Kepler spacecraft. However, the light curve of the star, a graph of its stellar flux versus time, showed that while there were regular drops in stellar flux approximately every 15 hours, the amount of light being blocked covered a wide range, from 0.2% to 1.3% of the starlight being blocked.[2] Rappaport et al. (2012) proposed various possible phenomena which may have caused the anomalies in the light curve, including two planets orbiting each other,[6] and an eclipsing binary orbiting the star in a larger triple-star system.[2] However, the authors found the hypothetical binary planet system to be unstable[2] and the latter scenario to be poorly supported by the data collected by Kepler.[2]

Therefore, the authors posited that the most likely cause of the observed light curve was a closely orbiting planet, about twice the mass of Mercury, which was rapidly emitting small particles into independent orbits around the star.[2] Exactly the cause of this phenomenon could be the direct sublimation of the planetary surface and its emission into space, the intense volcanism caused by the tidal effects of orbiting extremely close to the host star, or both processes mutually reinforcing the strength of each other in a positive feedback loop.[2]

Planetary system

The hypothetical planetary system of KIC 12557548 consists of one unconfirmed extrasolar planet, named KIC 12557548 b according to IAU rules. This planet may possess a tail of dust and gas formed in a similar fashion to that of a comet[4] 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 about 0.1 Earth masses — a higher-mass planet would have too much gravity to sustain the observed rate of mass loss, while a lower-mass planet may have already evaporated.[2]

The KIC 12557548 planetary system[2][4]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (unconfirmed) 0.1 M⊕ 0.013 (1208425.494 miles) 0.654 — — —

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. 1 2 3 4 5 6 "Basic data: 2MASS J19235189+5130170 -- Infra-Red source". SIMBAD. University of Stratsbourg. 2012. Retrieved June 9, 2012.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Rappaport, S.; Levine, A.; Chiang, E.; El Mellah, I.; Jenkins, J.; Kalomeni, B.; Kite, E. S.; Kotson, M.; Nelson, L.; Rousseau-Nepton, L.; Tran, K. (2012). "Possible Disintegrating Short-Period Super-Mercury Orbiting KIC 12557548". The Astrophysical Journal 752: 1. arXiv:1201.2662v2. Bibcode:2012ApJ...752....1R. doi:10.1088/0004-637X/752/1/1.
  3. 1 2 3 Ouellette, Jennifer (May 26, 2012). "Dust to Dust: The Death of an Exoplanet". Discovery News. Discovery Communications, LLC. Retrieved June 9, 2012.
  4. 1 2 3 Staff, Space.com (24 March 2012). "Possible Newfound Alien Planet is Falling to Pieces". Space.com. Retrieved June 9, 2012.
  5. ↑ "NASA's Kepler Detects Potential Evaporating Planet" (Press release). Jet Propulsion Laboratory. May 21, 2012. Retrieved June 11, 2012.
  6. ↑ Howard, Jacqueline (May 20, 2012). "Exoplanet Turning To Dust Under Parent Star's Intense Heat, Scientists Say". HuffPost Science. TheHuffingtonPost.com, Inc. Retrieved June 11, 2012.

Notes

  1. ↑ Calculated based on statements by Space.com regarding the orbital radius of the planet in terms of stellar diameters and the fact that this orbital radius was known from Rappaport et al. (2012).

External links

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