Fomalhaut with Disk Ring and extrasolar planet b

A debris disk (

American English American English, sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States. English is the Languages of the United States, most widely spoken lan ...

), or debris disc (

Commonwealth English The use of the English language in current and former Member states of the Commonwealth of Nations, member countries of the Commonwealth of Nations was largely inherited from British Empire, British colonisation, with some exceptions. English s ...

), is a

circumstellar disk A circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the ...

of dust and debris in orbit around a

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

. Sometimes these disks contain prominent rings, as seen in the image of

Fomalhaut Fomalhaut is the brightest star in the southern constellation of Piscis Austrinus, the "Southern Fish", and one of the brightest stars in the night sky. It has the Bayer designation Alpha Piscis Austrini, which is Latinized from � ...

on the right. Debris disks are found around stars with mature planetary systems, including at least one debris disk in orbit around an evolved

neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...

. Debris disks can also be produced and maintained as the remnants of collisions between planetesimals, otherwise known as asteroids and comets. By 2001, more than 900 candidate stars had been found to possess a debris disk. They are usually discovered by examining the star system in

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

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. Debris disks are often described as massive analogs to the debris in the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

. Most known debris disks have radii of 10–100

astronomical unit The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits t ...

s (AU); they resemble the

Kuiper belt The Kuiper belt () is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

in the Solar System, although the Kuiper belt does not have a high enough dust mass to be detected around even the nearest stars. Some debris disks contain a component of warmer dust located within 10 AU from the central star. This dust is sometimes called

exozodiacal dust Exozodiacal dust is 1–100 micrometre-sized grains of amorphous carbon and silicate dust that fill the plane of extrasolar planetary systems. It is the exoplanetary analog of zodiacal dust, the 1–100 micrometre-sized dust grains observed in ...

by analogy to

zodiacal dust The interplanetary dust cloud, or zodiacal cloud (as the source of the zodiacal light), consists of cosmic dust (small particles floating in outer space) that pervades the space between planets within planetary systems, such as the Solar System ...

in the Solar System.

Observation history

VLT and Hubble images of the disc around AU Microscopii

In 1984 a debris disk was detected around the star

Vega Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, an ...

using the

IRAS The Infrared Astronomical Satellite (Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mo ...

satellite. Initially this was believed to be a

protoplanetary disk A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for the star itself, be ...

, but it is now known to be a debris disk due to the lack of gas in the disk and the age of the star. The first four debris disks discovered with IRAS are known as the "fabulous four":

, Beta Pictoris,

, and

Epsilon Eridani Epsilon Eridani ( Latinized from ε Eridani), formally named Ran, is a star in the southern constellation of Eridanus, at a declination of 9.46° south of the celestial equator. This allows it to be visible from most of Earth's surf ...

. Subsequently, direct images of the Beta Pictoris disk showed irregularities in the dust, which were attributed to gravitational perturbations by an unseen

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

. That explanation was confirmed with the 2008 discovery of the exoplanet

Beta Pictoris b Beta Pictoris b (abbreviated as β Pic b) is an exoplanet orbiting the young debris disk A-type main sequence star Beta Pictoris located approximately 63 light-years (19.4 parsecs, or km) away from Earth in the constellation of Pictor. It has ...

. Other exoplanet-hosting stars, including the first discovered by direct imaging (

HR 8799 HR 8799 is a roughly 30 million-year-old main-sequence star located away from Earth in the constellation of Pegasus. It has roughly 1.5 times the Sun's mass and 4.9 times its luminosity. It is part of a system that also ...

), are known to also host debris disks. The nearby star 55 Cancri, a system that is also known to contain five planets, also was reported to have a debris disk, but that detection could not be confirmed. Structures in the debris disk around

suggest perturbations by a planetary body in orbit around that star, which may be used to constrain the mass and orbit of the planet. 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 The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

, by using newly improved imaging processes. In 2021, observations of a star, VVV-WIT-08, that became obscured for a period of 200 days may have been the result of a debris disk passing between the star and observers on Earth. Two other stars,

Epsilon Aurigae Epsilon Aurigae (ε Aurigae, abbreviated Epsilon Aur, ε Aur) is a multiple star system in the northern constellation of Auriga, the charioteer. It is an unusual eclipsing binary system comprising an F0 supergiant (officially named Alma ...

and TYC 2505-672-1, are reported to be eclipsed regularly and it has been determined that the phenomenon is the result of disks orbiting them in varied periods, suggesting that VVV-WIT-08 may be similar and have a much longer orbital period that just has been experienced by observers on Earth. VVV-WIT-08 is ten times the size of the Sun in the constellation of Sagittarius.

Origin

NASA-14114-HubbleSpaceTelescope-DebrisDisks-20140424

During the formation of a Sun-like star, the object passes through the T-Tauri phase during which it is surrounded by a gas-rich, disk-shaped nebula. Out of this material are formed

planetesimal Planetesimals are solid objects thought to exist in protoplanetary disks and debris disks. Per the Chamberlin–Moulton planetesimal hypothesis, they are believed to form out of cosmic dust grains. Believed to have formed in the Solar System a ...

s, which can continue accreting other planetesimals and disk material to form planets. The nebula continues to orbit the

pre-main-sequence star A pre-main-sequence star (also known as a PMS star and PMS object) is a star in the stage when it has not yet reached the main sequence. Earlier in its life, the object is a protostar that grows by acquiring mass from its surrounding envelope of ...

for a period of until it is cleared out by radiation pressure and other processes. Second generation 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 may cause a disk to persist for much of the lifetime of a star. 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 In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...

pressure from the host

. In very tenuous disks such as the ones in the Solar System, the

Poynting–Robertson effect The Poynting–Robertson effect, also known as Poynting–Robertson drag, named after John Henry Poynting and Howard P. Robertson, is a process by which solar radiation causes a dust grain orbiting a star to lose angular momentum relative to its o ...

can cause particles to

spiral In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. Helices Two major definitions of "spiral" in the American Heritage Dictionary are: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. 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 A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

companion or the close approach of another star. The presence of a debris disk may indicate a high likelihood of

exoplanets An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

orbiting the star. Furthermore, many debris disks also show structures within the dust (for example, clumps and warps or asymmetries) that point to the presence of one or more exoplanets within the disk. The presence or absence of asymmetries in our own trans-Neptunian belt remains controversial although they might exist.

Known belts

Belts of dust or debris have been detected around many stars, including the Sun, including the following: 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 Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

has an average distance from the Sun of 1 AU.

References

External links

* {{cite web , last = McCabe , first = Caer , date =2019-03-08 , url =http://www.circumstellardisks.org/ , title =Catalog of Resolved Circumstellar Disks , publisher = NASA JPL , access-date =2019-03-08 *Debris disk

Observation history

Origin

Known belts

See also

References

External links