Debris disk

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Debris disk around star AU Microscopii. Image taken by Hubble Space Telescope
Debris disk around star AU Microscopii. Image taken by Hubble Space Telescope

A debris disk is a ring-shaped circumstellar disk of dust and debris in orbit around a star. Debris disks have been found around both evolved and young stars, as well as at least one debris disk in orbit around a neutron star.[1] They can constitute a phase in the formation of a planetary system following the protoplanetary disk phase.[2] They can also be produced and maintained as the remnants of collisions between planetismals.[3]

By 2001, over 900 candidate stars have been found to possess a debris disk. They are usually located by examining the star system in infrared light and looking for an excess of radiation beyond that emitted by the star. This excess is inferred to be radiation from the star that has been absorbed by the disk, then radiated away as infrared energy.[4]

In certain cases the debris disks can be observed directly by occulting the primary star and then imaging the system.

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[edit] Observation history

In 1984 a debris disk was located in orbit around the star Vega using the IRAS satellite. Initially this was believed to be a protoplanetary disk, but it is now thought to be a debris disk due to the lack of gas in the disk. Subsequently irregularities have been found in the disk, which may be indicative of the presence of planetary bodies.[5] Similar discoveries of debris disks were made around the stars Fomalhaut and Beta Pictoris.

By 1998 a debris disk had been located around the nearby star 55 Cancri, a system that is also known to contain a planet.[6] Structures in the debris disk around Epsilon Eridani also suggest perturbations by a planetary body in orbit around that star, which may be used to constrain the mass and orbit of the planet.[7]

[edit] Origin

Typical debris disks contain small grains 1–100 μm in size. Radiation from the host star can cause these particles to spiral inward because of the Poynting-Robertson effect, so the lifetime of the disk will be on the order of 10 Myr or less. Thus, for a disk to remain intact, a process is needed to continually replenish the disk. This can occur, for example, by means of collisions between larger bodies. This can occur on a continual basis as collisions grind objects down into ever smaller bodies.[8]

For collisions to occur in a debris disk, the bodies must be gravitationally perturbed sufficiently to create relatively large collisional velocities. A planetary system around the star can cause such perturbations, as can a binary star companion or the close approach of another star.[8]

[edit] Known belts

Belts of dust or debris have also been detected around stars other than the Sun, including the following:

Star Spectral
class[9]		 Distance
(ly)		 Orbit
(AU)
Epsilon Eridani[7] K2V 10.5 35–75
Tau Ceti[10] G8V 11.9 35–50
Vega[5][11] A0V 25 86–200
AU Microscopii[12] M1Ve 33 50–150
HD 69830[13] K0V 41 <1
55 Cancri A[6] G8V 41 27–50
Pi1 Ursae Majoris[14] G1.5Vb 46.5  ?
HD 139664[15] F5IV-V 57 60–109
Eta Corvi[16] F2V 59 100–150
HD 53143[15] K1V 60  ?
Beta Pictoris[11] A5V 63 25–550
Zeta Leporis[17] A2Vann 70 2–8
HD 92945[18] K1V 72 45–175
HD 107146[19] G2V 88 130
Fomalhaut[5] A3V 133 25
HD 12039[20] G3-5V 137 5
HD 15115[21] F2V 150 315–550
HR 4796 A[22][23] A0V 220 200
HD 141569[23] B9.5e 320 400
HD 113766 A[24] F4V 430 0.35–5.8

The orbital distance of the belt is an estimated mean distance or range, based either on direct measurement from imaging or derived from the temperature of the belt. The Earth has an average distance from the Sun of 1 AU.

[edit] See also

[edit] References

  1. ^ Z. Wang, D. Chakrabarty, D. L. Kaplan (2006). "A debris disk around an isolated young neutron star". Nature 440 (7085): 772–775. doi:10.1038/nature04669. 
  2. ^ "Spitzer Team Says Debris Disk Could Be Forming Infant Terrestrial Planets", NASA, December 14, 2005. Retrieved on 2007-01-03. 
  3. ^ "Spitzer Sees Dusty Aftermath of Pluto-Sized Collision", NASA, January 10, 2005. Retrieved on 2007-01-03. 
  4. ^ Debris Disk Database. Royal Observatory Edinburgh. Retrieved on 2007-01-03.
  5. ^ a b c Joint Astronomy Centre (April 21, 1998). "Astronomers discover possible new Solar Systems in formation around the nearby stars Vega and Fomalhaut". Press release. Retrieved on 2006-04-24.
  6. ^ a b "University Of Arizona Scientists Are First To Discover Debris Disk Around Star Orbited By Planet", ScienceDaily, October 23, 1998. Retrieved on 2006-05-24. 
  7. ^ a b J.S. Greaves; W.S. Holland; M.C. Wyatt; W.R.F. Dent; E.I. Robson; I.M. Coulson; T. Jenness; G.H. Moriarty-Schieven; G.R. Davis; H.M. Butner; W.K. Gear; C. Dominik; H. J. Walker (2005). "Structure in the Epsilon Eridani Debris Disk" ([dead link] – Scholar search). The Astrophysical Journal 619: L187 – L190. doi:10.1086/428348. 
  8. ^ a b Scott Kenyon & Benjamin Bromley (2007). Stellar Flybys & Planetary Debris Disks. Smithsonian Astrophysical Observatory. Retrieved on 2007-07-23.
  9. ^ SIMBAD: Query by identifiers. Centre de Données astronomiques de Strasbourg. Retrieved on 2007-07-17.
  10. ^ J. S. Greaves, M. C. Wyatt, W. S. Holland, W. R. F. Dent (2004). "The debris disc around tau Ceti: a massive analogue to the Kuiper Belt". Monthly Notices of the Royal Astronomical Society 351 (3): L54–L58. doi:10.1111/j.1365-2966.2004.07957.x. 
  11. ^ a b Backman, D. E. (1996). "Dust in beta PIC / VEGA Main Sequence Systems". Bulletin of the American Astronomical Society 28: 1056. 
  12. ^ Sanders, Robert. "Dust around nearby star like powder snow", UC Berkeley News, January 8, 2007. Retrieved on 2007-01-11. 
  13. ^ Lisse, C. M.; Beichman, C. A.; Bryden, G.; Wyatt, M. C. (1999). "On the Nature of the Dust in the Debris Disk around HD 69830". The Astrophysical Journal 658 (1): 584–592. doi:10.1086/511001. 
  14. ^ Beichman, C. A.; Tanner, A.; Bryden, G.; Stapelfeldt, K. R.; Werner, M. W.; Rieke, G. H.; Trilling, D. E.; Lawler, S.; Gautier, T. N. (2006). "IRS Spectra of Solar-Type Stars: A Search for Asteroid Belt Analogs". The Astrophysical Journal 639: 1166–1176. doi:10.1086/499424. 
  15. ^ a b Kalas, Paul; Graham, James R.; Clampin, Mark C.; Fitzgerald, Michael P. (2006). "First Scattered Light Images of Debris Disks around HD 53143 and HD 139664". The Astrophysical Journal 637 (1): L57–L60. doi:10.1086/500305. 
  16. ^ Wyatt, M. C.; Greaves, J. S.; Dent, W. R. F.; Coulson, I. M. (2005). "Submillimeter Images of a Dusty Kuiper Belt around Corvi" ([dead link] – Scholar search). The Astrophysical Journal 620: 492–500. doi:10.1086/426929. 
  17. ^ M. M. Moerchen, C. M. Telesco, C. Packham, T. J. J. Kehoe (2006). "Mid-infrared resolution of a 3 AU-radius debris disk around Zeta Leporis". Astrophysical Journal Letters. 
  18. ^ D. Golimowski et al (2007). Observations and Models of the Debris Disk around K Dwarf HD 92945. University of California, Berkeley Astronomy Department. Retrieved on 2007-07-17.
  19. ^ Jonathan P. Williams et al (2004). "Detection of cool dust around the G2V star HD 107146". Astrophysical Journal 604: 414–419. doi:10.1086/381721. 
  20. ^ Hines, Dean C. et al (2006). "The Formation and Evolution of Planetary Systems (FEPS): Discovery of an Unusual Debris System Associated with HD 12039". The Astrophysical Journal 638 (2): 1070–1079. doi:10.1086/498929. 
  21. ^ Kalas, Paul; Fitzgerald, Michael P.; Graham, James R. (2007). "Discovery of Extreme Asymmetry in the Debris Disk Surrounding HD 15115". The Astrophysical Journal 661 (1): L85–L88. doi:10.1086/518652. 
  22. ^ Koerner, D. W.; Ressler, M. E.; Werner, M. W.; Backman, D. E. (1998). "Mid-Infrared Imaging of a Circumstellar Disk around HR 4796: Mapping the Debris of Planetary Formation". Astrophysical Journal Letters 503: L83. doi:10.1086/311525. 
  23. ^ a b Villard, Ray; Weinberger, Alycia; Smith, Brad (January 8, 1999). Hubble Views of Dust Disks and Rings Surrounding Young Stars Yield Clues. HubbleSite. Retrieved on 2007-06-17.
  24. ^ Meyer, M. R.; Backman, D.. "Belt of Material Around Star May Be First Step in Terrestrial Planet Formation", University of Arizona, NASA, January 08, 2002. Retrieved on 2007-07-17. 

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