Active asteroid
An active asteroid is an asteroid that loses dust or gas, for any reason, making it look briefly like a comet.
An active asteroid is any object with an asteroid-like orbit that shows comet-like activity, such as a dust tail or coma. Main-belt comets, driven by ice, are one kind, but activity can also have other causes.
These include collisions, in which a small asteroid hits a larger one and throws out a dust cloud; rapid spinning, which can make a rubble pile shed material; and heat cracking near the Sun. The asteroid 3200 Phaethon, parent of the Geminid meteor shower, brightens near perihelion and releases small amounts of dust and sodium, probably because it is heated to around 750 °C.
In 2010, the asteroid P/2010 A2 was seen with an X-shaped debris pattern, best explained by a collision. The DART impact in 2022 deliberately turned Dimorphos into an active asteroid with a long debris tail. Active asteroids show that the asteroid belt is not static but continually losing material.
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Level: Expert Advanced