A debris disk is a circumstellar disk

Circumstellar disk

A circumstellar disk is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a star. Around the youngest stars, they are the reservoirs of material out of which planets may form...

 of dust and debris in orbit around a star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

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

Fomalhaut

Fomalhaut is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in the sky. Fomalhaut can be seen low in the southern sky in the northern hemisphere in fall and early winter evenings. Near latitude 50˚N, it sets around the time Sirius rises, and does not...

 on the right. 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

Neutron star

A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...

. They can constitute a phase in the formation of a planetary system following the protoplanetary disk

Protoplanetary disk

A protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star...

 phase. They can also be produced and maintained as the remnants of collisions between planetismals.

By 2001, over 900 candidate stars had been found to possess a debris disk. They are usually located by examining the star system in infrared

Infrared

Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 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.

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

Solar System

The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

. Most known debris disks have radii of 10–100 astronomical unit

Astronomical unit

An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....

s (AU); they resemble the Kuiper belt

Kuiper belt

The Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 50 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive...

 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

Exozodiacal dust

Exozodiacal dust is the exoplanetary analog of zodiacal dust, the 1-100 micrometre-sized grains of silicate dust that fill the plane of the solar system, especially interior to the asteroid belt. As for the zodiacal dust, these grains are probably produced by outgasing comets as well as by...

 by analogy to zodiacal dust

Zodiacal dust

The Zodiacal dust cloud is visible as a diffuse glow, known as the zodiacal light, that stretches along the zodiac, and is best seen just after sunset and before sunrise in spring and autumn when the zodiac is at a steep angle to the horizon....

 in the Solar System.

Observation history

In 1984 a debris disk was detected around the star Vega

Vega

Vega is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus...

 using the IRAS

IRAS

The Infrared Astronomical Satellite was the first-ever space-based observatory to perform a survey of the entire sky at infrared wavelengths....

 satellite. Initially this was believed to be a protoplanetary disk

Protoplanetary disk

A protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star...

, 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. Similar discoveries of
debris disks were made around the stars Fomalhaut

Fomalhaut

Fomalhaut is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in the sky. Fomalhaut can be seen low in the southern sky in the northern hemisphere in fall and early winter evenings. Near latitude 50˚N, it sets around the time Sirius rises, and does not...

 and
Beta Pictoris

Beta Pictoris

Beta Pictoris is the second brightest star in the constellation Pictor. It is located 63.4 light years from our solar system, and is 1.75 times as massive and 8.7 times as luminous as the Sun. The Beta Pictoris system is very young, only 8–20 million years old, although it is already in the main...

.

The nearby star 55 Cancri

55 Cancri

55 Cancri , also cataloged Rho1 Cancri or abbreviated 55 Cnc, is a binary star approximately 41 light-years away from Earth in the constellation of Cancer...

, a system that is also known to contain five planets, was reported to also have a debris disk, but that detection could not be confirmed.
Structures in the debris disk around Epsilon Eridani

Epsilon Eridani

Epsilon Eridani is a star in the southern constellation Eridanus, along a declination 9.46° south of the celestial equator. This allows the star to be viewed from most of the Earth's surface. At a distance of 10.5 light years , it has an apparent magnitude of 3.73...

 suggest perturbations by a planetary body in orbit around that star, which may be used to constrain the mass and orbit of the planet.

Origin

During the formation of a Sun-like star, the object passes through the T-Tauri

T Tauri star

T Tauri stars are a class of variable stars named after their prototype – T Tauri. They are found near molecular clouds and identified by their optical variability and strong chromospheric lines.-Characteristics:...

 phase during which it is surrounded by a disk-shaped nebula. Out of this material are formed planetesimal

Planetesimal

Planetesimals are solid objects thought to exist in protoplanetary disks and in debris disks.A widely accepted theory of planet formation, the so-called planetesimal hypothesis of Viktor Safronov, states that planets form out of cosmic dust grains that collide and stick to form larger and larger...

s, which can undergo an accretion process to form planets. The nebula continues to orbit the pre-main-sequence star for a period of until it is cleared out by radiation pressure. Additional dust may then be generated about the star by collisions between the planetismals, which forms a disk out of the resulting debris. At some point during their lifetime, about 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.

Typical debris disks contain small grains 1–100 μm

Micrometre

A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

 in size. Collisions will grind down these grains to sub-micrometre sizes, which will be removed from the system by radiation

Radiation

In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

 pressure from the host star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

. In very tenuous disks like the ones in the Solar System, the Poynting–Robertson effect can cause particles to spiral

Spiral

In mathematics, a spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.-Spiral or helix:...

 inward instead. Both processes limit the lifetime of the disk to 10 Myr

Myr

The symbol myr was formerly used in English-language geology, and remains as the standard usage in astronomy, as a unit of one million years.It is an abbreviation for 'million years' and lower case is used in geology, while upper case is used in astronomy....

 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

Perturbation (astronomy)

Perturbation is a term used in astronomy in connection with descriptions of the complex motion of a massive body which is subject to appreciable gravitational effects from more than one other massive body....

 sufficiently to create relatively large collisional velocities. A planetary system around the star can cause such perturbations, as can a binary star

Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

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

Terrestrial planet

A terrestrial planet, telluric planet or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun...

s orbiting the star.

Known belts

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

Star	Spectral class	Distance (ly)	Orbit (AU Astronomical unit An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance.... )	Notes
Epsilon Eridani Epsilon Eridani Epsilon Eridani is a star in the southern constellation Eridanus, along a declination 9.46° south of the celestial equator. This allows the star to be viewed from most of the Earth's surface. At a distance of 10.5 light years , it has an apparent magnitude of 3.73...	K2V	10.5	35–75
Tau Ceti Tau Ceti Tau Ceti is a star in the constellation Cetus that is spectrally similar to the Sun, although it has only about 78% of the Sun's mass. At a distance of just under 12 light-years from the Solar System, it is a relatively close star. Tau Ceti is metal-deficient and so is thought to be less likely to...	G8V	11.9	35–50
Vega Vega Vega is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus...	A0V	25	86–200
Fomalhaut Fomalhaut Fomalhaut is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in the sky. Fomalhaut can be seen low in the southern sky in the northern hemisphere in fall and early winter evenings. Near latitude 50˚N, it sets around the time Sirius rises, and does not...	A3V	25	133–158
AU Microscopii AU Microscopii AU Microscopii is a red dwarf star located 10 parsecs away – about 8 times as far as our closest star after the Sun. AU Mic is a young star, only 12 million years old, less than 1% of the age of the Sun. It has only half the mass of the Sun and is only one-tenth as bright...	M1Ve	33	50–150
HD 69830 HD 69830 HD 69830 is an orange dwarf star approximately 41 light-years away in the constellation of Puppis. It has the Gould designation 285 G. Puppis, though this is infrequently used. In 2005, the Spitzer Space Telescope discovered a debris disk orbiting the star. The disk contains substantially more...	K0V	41	<1
55 Cancri 55 Cancri 55 Cancri , also cataloged Rho1 Cancri or abbreviated 55 Cnc, is a binary star approximately 41 light-years away from Earth in the constellation of Cancer...  A	G8V	41	27–50
Pi1 Ursae Majoris Pi1 Ursae Majoris Pi¹ Ursae Majoris is a yellow G-type main sequence dwarf with a mean apparent magnitude of +5.63. It is approximately 46.8 light years from Earth, and is a relatively young star with an age of about 200 million years. It is classified as a BY Draconis type variable star and its brightness varies by...	G1.5Vb	46.5	?
HD 207129	G0V	52	148–178
HD 139664	F5IV–V	57	60–109
Eta Corvi Eta Corvi Eta Corvi is an F-type main sequence star, the sixth-brightest star in the constellation of Corvus. Two debris disks have been detected orbiting this star, one warm within a few AU and another out at ~150 AU.-Properties:This star is about 40% more massive than the Sun but is only about 30% of...	F2V	59	100–150
HD 53143 HD 53143 HD 53143 is an orange main sequence star that is located about 60 light years from the Sun. It is about a billion years in age and lies within the Carina constellation. A debris disk has been found in a wide orbit around this star....	K1V	60	?
Beta Pictoris Beta Pictoris Beta Pictoris is the second brightest star in the constellation Pictor. It is located 63.4 light years from our solar system, and is 1.75 times as massive and 8.7 times as luminous as the Sun. The Beta Pictoris system is very young, only 8–20 million years old, although it is already in the main...	A6V	63	25–550
Zeta Leporis Zeta Leporis Zeta Leporis is a white main sequence star approximately 70 light-years away in the constellation of Lepus. The star is suspected of being a spectroscopic binary star system, but this is yet to be confirmed. In 2001, an asteroid belt was confirmed to orbit the star.-Stellar components:Zeta...	A2Vann	70	2–8
HD 92945 HD 92945 HD 92945 is a K-type main sequence star in the constellation of Hydra. Its apparent visual magnitude varies by 0.02 magnitudes and is approximately 7.72 at maximum brightness. A debris disk has been observed around the star by coronagraphic imaging, using the ACS and NICMOS instruments on...	K1V	72	45–175
HD 107146 HD 107146 HD 107146 is a G2V star, located 88 light years from Earth. In 2003, astronomers recognized the excess infrared and submillimeter emission indicative of circumstellar dust, the first time such a debris disk phenomenon was noted around a star of similar spectral types as the Sun, though having a...	G2V	88	130
HR 8799 HR 8799 HR 8799 is a young main sequence star located 129 light years away from Earth in the constellation of Pegasus, with roughly 1.5 times the Sun's mass and 4.9 times its luminosity. It is part of a system that also contains a debris disk and at least four massive planets...	A5V	129	75
51 Ophiuchi 51 Ophiuchi 51 Ophiuchi is a young B-type star, lying approximately away in the constellation Ophiuchus, northwest of the center of the Milky Way...	B9	131	0.5–1200
HD 12039 HD 12039 HD 12039 is a variable star in the constellation of Cetus. It is categorized as a BY Draconis variable, and has a stellar classification that is similar to our own Sun....	G3–5V	137	5
HD 98800 HD 98800 HD 98800, also catalogued as TV Crateris , is a quadruple star system approximately 150 light-years away in the constellation of Crater . The system is located within the TW Hydrae association...	K5e (?)	150	1
HD 15115 HD 15115 HD 15115 is a yellow-white star.The asymmetric disk encircling the star was discovered using the Hubble Space Telescope and further investigated by the W.M...	F2V	150	315–550
HR 4796 HR 4796 HR 4796 is a binary star system approximately 220 light-years away in the constellation of Centaurus. The system includes an A-type main sequence star and a red dwarf star. The primary star is twice as massive as the Sun and twenty times more luminous. It is thought to be approximately 8 million...  A	A0V	220	200
HD 141569 HD 141569 HD 141569 is a blue-white dwarf star approximately 320 light-years away in the constellation of Libra. The primary star has two red dwarf companions at about nine arseconds. In 1999, a protoplanetary disk was discovered around the star...	B9.5e	320	400
HD 113766 HD 113766 HD 113766 is a binary star system located 424 ly from Earth in the direction of the constellation Centaurus. The star system is approximately 10 million years old and is slightly more massive than our sun, but what makes HD 113766 special is the presence of a large belt of warm dust surrounding...  A	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

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

has an average distance from the Sun of 1 AU.