Debris disk

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Hubble Space Telescope observation of the debris ring around Fomalhaut. The inner edge of the disk may have been shaped by the orbit of Fomalhaut b, at lower right.

A debris disk is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris disks have been found around both mature and young stars, as well as at least one debris disk in orbit around an evolved neutron star.[1] Younger debris disks can constitute a phase in the formation of a planetary system following the protoplanetary disk phase, when terrestrial planets may finish growing.[2] They can also be produced and maintained as the remnants of collisions between planetesimals, otherwise known as asteroids and comets.[3]

By 2001, over 900 candidate stars had been found to possess a debris disk. They are usually discovered 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 dust in the disk, then re-radiated away as infrared energy.[4]

Debris disks are often described as massive analogs to the debris in the Solar System. Most known debris disks have radii of 10–100 astronomical units (AU); they resemble the Kuiper belt in the Solar System, but with much more dust. Some debris disks contain a component of warmer dust located within 10 AU from the central star. This dust is sometimes called exozodiacal dust by analogy to zodiacal dust in the Solar System.

Observation history[edit]

VLT and Hubble images of the disc around AU Microscopii.[5]

In 1984 a debris disk was detected 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 and the age of the star. Subsequently irregularities have been found in the disk, which may be indicative of the presence of planetary bodies.[6] Similar discoveries of debris disks were made around the stars Fomalhaut and Beta Pictoris.

The nearby star 55 Cancri, a system that is also known to contain five planets, was reported to also have a debris disk,[7] but that detection could not be confirmed.[8] Structures in the debris disk around Epsilon Eridani suggest perturbations by a planetary body in orbit around that star, which may be used to constrain the mass and orbit of the planet.[9]

On 24 April 2014, NASA reported detecting debris disks in archival images of several young stars, HD 141943 and HD 191089, first viewed between 1999 and 2006 with the Hubble Space Telescope, by using newly improved imaging processes.[10]


Debris disks detected in HST archival images of young stars, HD 141943 and HD 191089, using improved imaging processes (24 April 2014).[10]

During the formation of a Sun-like star, the object passes through the T-Tauri phase during which it is surrounded by a disk-shaped nebula. Out of this material are formed planetesimals, which can undergo an accretion process to form planets. The nebula continues to orbit the pre-main-sequence star for a period of 1–20 million years until it is cleared out by radiation pressure and other processes. Additional dust may then be generated about the star by collisions between the planetesimals, which forms a disk out of the resulting debris. At some point during their lifetime, at least 45% of these stars are surrounded by a debris disk, which then can be detected by the thermal emission of the dust using an infrared telescope. Repeated collisions can cause a disk to persist for much of the lifetime of a star.[11]

Typical debris disks contain small grains 1–100 μm in size. Collisions will grind down these grains to sub-micrometre sizes, which will be removed from the system by radiation pressure from the host star. In very tenuous disks like the ones in the Solar System, the Poynting–Robertson effect can cause particles to spiral inward instead. Both processes limit the lifetime of the disk to 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, followed by a cascade that grinds down the objects to the observed small grains.[12]

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.[12] The presence of a debris disk may indicate a high likelihood of terrestrial planets orbiting the star.[13]

Known belts[edit]

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

Star Spectral
Epsilon Eridani K2V 10.5 35–75 [9]
Tau Ceti G8V 11.9 35–50 [15]
Vega A0V 25 86–200 [6][16]
Fomalhaut A3V 25 133–158 [6]
AU Microscopii M1Ve 33 50–150 [17]
HD 181327 F5.5V 51.8 89-110 [18]
HD 69830 K0V 41 <1 [19]
HD 207129 G0V 52 148–178 [20]
HD 139664 F5IV–V 57 60–109 [21]
Eta Corvi F2V 59 100–150 [22]
HD 53143 K1V 60  ? [21]
Beta Pictoris A6V 63 25–550 [16]
Zeta Leporis A2Vann 70 2–8 [23]
HD 92945 K1V 72 45–175 [24]
HD 107146 G2V 88 130 [25]
Gamma Ophiuchi A0V 95 520 [26]
HR 8799 A5V 129 75 [27]
51 Ophiuchi B9 131 0.5–1200 [28]
HD 12039 G3–5V 137 5 [29]
HD 98800 K5e (?) 150 1 [30]
HD 15115 F2V 150 315–550 [31]
HR 4796 A A0V 220 200 [32][33]
HD 141569 B9.5e 320 400 [33]
HD 113766 A F4V 430 0.35–5.8 [34]
HD 141943 [10]
HD 191089 [10]

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.

See also[edit]


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  7. ^ "University Of Arizona Scientists Are First To Discover Debris Disk Around Star Orbited By Planet". ScienceDaily. 1998-10-03. Retrieved 2006-05-24. 
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  9. ^ a b Greaves, J. S.; Holland, W. S.; Wyatt, M. C.; Dent, W. R. F.; Robson, E. I.; Coulson, I. M.; Jenness, T.; Moriarty-Schieven, G. H.; Davis, G. R.; Butner, H. M.; Gear, W. K.; Dominik, C.; Walker, H. J. (2005). "Structure in the Epsilon Eridani Debris Disk". The Astrophysical Journal. 619 (2): L187 – L190. Bibcode:2005ApJ...619L.187G. doi:10.1086/428348. 
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  24. ^ Golimowski, D.; et al. (2007). "Observations and Models of the Debris Disk around K Dwarf HD 92945" (PDF). University of California, Berkeley Astronomy Department. Retrieved 2007-07-17. 
  25. ^ Williams, Jonathan P., et al. (2004). "Detection of cool dust around the G2V star HD 107146". Astrophysical Journal. 604 (1): 414–419. arXiv:astro-ph/0311583free to read. Bibcode:2004ApJ...604..414W. doi:10.1086/381721. 
  26. ^ SU, K.Y.L.; et al. (2008). "The exceptionally large debris disk around γ Ophiuchi". Astrophysical Journal. 679 (2): L125–L129. arXiv:0804.2924free to read. Bibcode:2008ApJ...679L.125S. doi:10.1086/589508. 
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  28. ^ Stark, C.; et al. (2009). "51 Ophiuchus: A Possible Beta Pictoris Analog Measured with the Keck Interferometer Nuller". Astrophysical Journal. 703 (2): 1188–1197. arXiv:0909.1821free to read. Bibcode:2009ApJ...703.1188S. doi:10.1088/0004-637X/703/2/1188. 
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External links[edit]