BD+20°307

BD+20°307 is a close binary star system approximately 300 light-years away in the constellation Aries. The system is surrounded by a dusty ring,[2][3] and probably orbited by a 0.48M☉ white dwarf on a wide (980 AU) orbit.[4]

BD+20°307

An artist's impression of two planets colliding in the system.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Aries
Right ascension 01h 54m 50.3443s
Declination +21° 18′ 22.477″
Apparent magnitude (V) 9.01
Characteristics
Spectral type G0V
U−B color index 0.559
Astrometry
Proper motion (μ) RA: 38.789[1] mas/yr
Dec.: -22.636[1] mas/yr
Parallax (π)8.3341 ± 0.0464 mas[1]
Distance391 ± 2 ly
(120.0 ± 0.7 pc)
Details
Mass1/1 M☉
Radius1/1 R☉
Luminosity1/2 L☉
Age>1 × 109 years
Other designations
BD+20°307, 2MASS J01545034+2118225, TYC 1212-207-1, AG+21° 173, HIP 8920, PPM 91187, YZ 21 572, GSC 01212-00207, IRAS 01520+2103, SAO 75016.
Database references
SIMBADdata

The dust that orbits around several hundred main-sequence stars is cold and comes from a Kuiper-belt analogous region. In the Solar System the ongoing collisions between asteroids generate a tenuous cloud of dust known as the zodiacal light. When the Solar System was young such collisions were more common and the rate of dust production was probably many times higher. Zodiacal dust around stars much younger than the Sun has been rarely found. Only a few main-sequence stars have revealed warm (>120 K) zodiacal dust.

An exceptionally large amount of warm, small, silicate dust particles around the solar-type star BD+20°307 (HIP 8920, SAO 75016) has been reported.[5] The composition, quantity and temperature of the dust may be explained by recent, frequent or huge collisions between asteroids or other planetesimals whose orbits are being perturbed by a nearby planet.[5]

Spectroscopic binary

Both stars of the close binary are considered to be Solar-type stars that are slightly more massive than the Sun. The two stars differ in effective temperature by only ~250 K and have a mass ratio of 0.91.[6] The two orbit a common center of mass every 3.42 days. Within the spectra of the two stars the Li lines show different equivalent widths.[6] The Li 6707 Å line though weak is detected only from the primary star, suggesting that it is older than 1 Gyr.[6] If so, the large amount of zodiacal dust around the binary must be from a very large and recent collision of planetesimals.[6]

Age

Recent measurements indicate that the binary star system has an age of several billion years — comparable to the Solar System.[7]

Dust cloud

The dust cloud orbiting BD+20°307 has about 1 million times more dust than is orbiting the Sun. Furthermore, the dust is made up of extremely tiny particles, and its temperature is over 100 K, which is unusually high. It is hypothesized that, within the past few hundred thousand years and perhaps much more recently, these particles were formed by a collision between two bodies similar to Earth. "It's as if Earth and Venus collided," said Prof. Benjamin Zuckerman, UCLA professor of physics and astronomy.[7] "Astronomers have never seen anything like this before. Apparently, major catastrophic collisions can take place in a fully mature planetary system."[7] This hypothesis explains why the bulk of this dust has not spiraled into BD+20°307, or been pushed out by stellar winds yet.[7] The National Science Foundation (NSF), NASA, Tennessee State University (TSU) and the State of Tennessee funded the work by Zuckerman and his collaborators.[7]

Sun-like stars with hot dust

As of 2006 there were 7 sun-like stars that have hot dust at < 10 AU.[8] These are

Sun-like Stars with Hot Dust Disks
Star Stellar 
classification		 Distance from 
Earth (ly)		 Constellation Dust (or Debris;
Temperature (K)		 System Dust (or Debris) 
Location (AU)		 Cool Dust > 10 AU Stellar Age (Myr)
η CorviF2V59Corvus> 80Unary< 3.5yes1500
HD 113766F3V424Centaurus~440Binary1.8yes [9]~10-16
BD+20°307G0V~300Aries> 100Binary1no> 1000
HD 72905G1.5Vb46.5Ursa MajorunknownUnary0.23[8]yes[8]400[8]
HD 12039G3-5V138Cetus110close stellar companion4-6no7.5-8
HD 69830K0V40.6Puppisunknown3 Neptune planets < 1 AU1no [9]2000 - 5000[8]
HD 98800BK5Ve~150CraterunknownBinary2.2 AU[8] inner disk 
~5.9 outer disk		no10

See also

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. Thompson, Maggie A.; et al. (12 April 2019). "Studying the Evolution of Warm Dust Encircling BD+20 307 Using SOFIA". The Astrophysical Journal. 875 (1): 45. arXiv:1903.03041. Bibcode:2019ApJ...875...45T. doi:10.3847/1538-4357/ab0d7f. S2CID 118634485.
  3. Bartels, Meghan (24 October 2019). "Bam! Scientists Watch Distant Exoplanet Collision". Space.com. Retrieved 24 October 2019.
  4. Moór, Attila; Ábrahám, Péter; Szabó, Gyula; Vida, Krisztián; Cataldi, Gianni; Derekas, Alíz; Henning, Thomas; Kinemuchi, Karen; Kóspál, Ágnes; Kovács, József; Pál, András; Sarkis, Paula; Seli, Bálint; Szabó, Zsófia M.; Takáts, Katalin (2021), "A New Sample of Warm Extreme Debris Disks from the ALLWISE Catalog", The Astrophysical Journal, 910 (1): 27, arXiv:2103.00568, Bibcode:2021ApJ...910...27M, doi:10.3847/1538-4357/abdc26, S2CID 232075830
  5. Song I, Zuckerman B, Weinberger AJ, Becklin EE (July 2005). "Extreme collisions between planetesimals as the origin of warm dust around a Sun-like star". Nature. 436 (7049): 363–5. Bibcode:2005Natur.436..363S. doi:10.1038/nature03853. PMID 16034411. S2CID 4390247.
  6. Weinberger AJ (May 2008). "On the Binary Nature of Dust-encircled BD+20 307". Astrophys. J. 679 (1): L41–4. arXiv:0804.1799. Bibcode:2008ApJ...679L..41W. doi:10.1086/589180. S2CID 747199.
  7. Britt, Robert Roy (23 September 2008). "Oh, My! When Worlds Really Collide". SPACE.com. Retrieved 7 July 2009.
  8. Wyatt MC, Smith R, Greaves JS, Beichman CA, Bryden G, Lisse CM (2007). "Transience of hot dust around Sun-like stars". Astrophys. J. 658 (1): 569–583. arXiv:astro-ph/0610102. Bibcode:2007ApJ...658..569W. doi:10.1086/510999. S2CID 6205766.
  9. Lisse, C.M.; Chen, C.; Wyatt, M.; Morlok, A. (2008). "Circumstellar Dust Created by Terrestrial Planet Formation Around HD113766A". Astrophys. J. 673 (1): 1122. arXiv:0710.0839. Bibcode:2008ApJ...673.1106L. doi:10.1086/523626. S2CID 3207468.
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