Tail discovered on asteroid hygiea
The SOCIETY for POPULAR ASTRONOMY
Electronic News Bulletin No. 387 2014 November 23
TAIL DISCOVERED ON ASTEROID HYGIEA
Carnegie Institution
A new active asteroid, numbered 62412, has been discovered in the main
asteroid belt between Mars and Jupiter. It is the first comet-like
object seen in the Hygiea family of asteroids. Active asteroids are a
newly recognised phenomenon and 62412 is only the 13th known active
asteroid in the main asteroid belt. It is estimated that there may
be about 100 of them in the main asteroid belt. Active asteroids
have stable orbits between Mars and Jupiter like other asteroids;
unlike other asteroids, however, they sometimes have the appearance of
comets, when dust or gas is ejected from their surfaces, creating a
sporadic tail effect. Astronomers recently discovered a tail on
62412, an object which had been known as an ordinary asteroid for over
a decade. The reasons for the loss of material and the formation of a
tail in active asteroids are unknown, although there are several
theories such as recent impacts or sublimation from solid to gas of
exposed ices.
In the past, asteroids were thought to be mostly unchanging objects,
but an improved ability to observe them has allowed scientists to
discover tails and comas, the latter being like the thin envelopes of
atmosphere surrounding comets' nuclei. Discoveries such as this one
can help researchers to determine the processes that cause some
asteroids to become active. They found that 62412 has a very fast
rotation that may shift surface material, some of which may leave the
surface and form the comet-like appearance. The tail may be created
directly from material ejected from the fast-rotating body, or from
ice within it subliming into water vapour after being freshly exposed
on the surface. The density of 62412 has been found to be typical of
primitive asteroids and not consistent with the much lower densities
comets.
