This is a list of collisions between exoplanets or planetesimals observed in extrasolar systems. These collisions are more common in young systems and are an important part in the growth of especially terrestrial planets from so-called planetary embryos. Detections of individual collisions are nevertheless rare and are detected via transits in the optical, infrared excess, silicate emission or via infrared brightening. Collisions are thought to be common in a type of debris disk, so-called extreme debris disks (EDD). Co-moving stellar or substellar companions can trigger such collisions at an old age, creating old EDDs. Only about 24 EDDs are known.
This list does not include planetary bodies being accreted by white dwarfs; these are listed at List of exoplanets and planetary debris around white dwarfs.
List of individual events This list contains systems with individual collision events that were directly observed. Alternatively events were inferred from properties of the disk. The list is sorted after the start of the event. Name of starspectral typeApprox. age(Myr)Extremedebrisdisk?Start of eventColliding bodiesNotesRef.Beta PictorisA6V20nomid-19th century100–500 km bodySo-called "cat's tail" feature in the disk observed in mid-infraredA few years before 2004Decreased mid-infrared flux and disappearance of forsterite emissionFomalhautA3V440noEarly 2004Two bodies of ≥110 km in size, or a 56 km body impacting a 893 km bodyFomalhaut b was once suspected to be a planet, but is now suspected to be the remains of a planetary collisionSeptember 2023two planetesimalscalled "Fomalhaut cs2", is 135.3 AU distant from the starTYC 4209-1322-1G1V275yes2010 or earlierunknownSometime in 2014Two ≥90 km bodiesbrightening and fading between 2014 and 2018P1121F9V80yesBefore 2012Two bodies with sizes of ≥100 kmOne hypervelocity impactNGC 2547–ID8G6V35yeslate 2012Two bodies with sizes of ≥100 kmlikely grazing or hit-and-run type eventearly 2014100 km bodies, maybe same objects as the first eventfragments dominated by bouldersHD 169142A5V6no2013–2018UnknownVariability interpreted as appearance and disappearance of a dust ring. Comparisons with EDDs were made.Gaia20ehkF5>10noAugust 2016two planetesimalsdust mass 4 × 1022 kg, orbit of 1.1 AU before infrared brighteningHD 166191late F- to early G10yesEarly 2018Two ≥500 km bodies, or Mars-sized planetary embryosSudden increase of dust production in early 2018, reaching a high in 2019. Also transit of star-sized dust clouds, produced by the collisions. Silica-rich material.V488 PerseiK2-2.5 V80yes2019Two 60 km bodies, or Mars-sized planetary embryosConstant collisions will last 1,000 to 10,000 years.Possibly formation of a Mercury-like planet. Silica-rich material.ASASSN-21qjG2300no?December 2021Two ice giantsBreakup of exocomets was also proposed.HD 172555A5V23noWithin 0.1 MyrTwo planetesimals, or Mars-sized planetary embryosCompared to the formation of the Moon. Silicate-rich material.BD+20 307F-type binary≥1000yesUnknownPlanetary-scaleCatastrophic collision between planetary-scale bodiesHD 15407AF3V80 or 2100yesUnknownMars-sized planetary embryosOne giant hypervelocity impact? Silica-rich material.HD 23514F6V100yesUnknownPlanetary embryos; later work: atmospheric stripping or giant impact, involving volatiles. Involving a mass at least corresponding to 120-165 km-size asteroid. Later work: Mars-sized planetary embryos.Member of the Pleiades. Silica-rich material.TYC 4479-3-1G6V5000yesUnknown≥50 km planetesimalDisruption of one bodyHD 113766AF2V17yesUnknownPartially differentiated bodiesRecent impact of two asteroids or planetary bodiesTYC 8830-410-1G9V600yesUnknownRocky bodiesGiant impactTYC 8105–370–1G9V130yesUnknownMars-sized planetary embryos.Silica-rich material.BD-04 3234 (TYC 4946–1106–1)F6V>150yesUnknownMars-sized planetary embryos.Silica-rich material. HD 181327 has an asymmetry in its disk that could be explained by a giant collision, but later research excluded this scenario. Bodies described as silica-rich in Su et al. 2026 originate from collisions between large planetary embryos (Mars-sized), silica-poor on the other hand are collisions between smaller bodies (Moon-sized) or involve less energetic impacts, such as low-velocity grazing impacts.
List of other EDDs These objects appear as EDDs in Moór et al. EDDs are listed here, because they are often associated with individual giant collisions. List is sorted after discovery year. Name of starSpectral typeApprox. age(Myr)NotesDiscovery yearRef.TYC 8241–2652–1K210rapid disappearance of the disk, unknown mechanism2012RZ PisciumK0IV30Intense continuous collisions, destroying a 90 km asteroid each year.2013TIC 43488669100-400runaway star, without further estimates of the collisions2020TYC 4515–485–1F5V>150without further estimates of the collisions2021TYC 5940–1510–1G5V120without further estimates of the collisions2021TYC 9196-2916-1K4.5V85without further estimates of the collisions20222MASS J06091701-1508085G9V200without further estimates of the collisions20242MASS J07120655-4752423K3.5V240without further estimates of the collisions2024CD-44 6765K0.5V5500without further estimates of the collisions20242MASS J20431522+1043355K4V250without further estimates of the collisions2024
List of EDD without collisions Name of starspectral typeapproximate age (Myr)notesdiscovery yearReferenceHD 145263F4V11hypervelocity impact was excluded in one study, instead extreme space weathering was suggested to explain observed mineralogy. This object appears as an EDD in Moór et al. Silica-rich material. Mars-sized planetary embryos.1998
See also List of stars that have unusual dimming periods List of largest craters in the Solar System Giant impact hypothesis Mercury is thought to have lost its mantle from a collision 354P/LINEAR small asteroid that was impacted by another asteroid
References