Comet Siding Spring is plunging toward the Sun along a roughly
1-million-year
orbit. The comet, discovered in 2013, was within the radius of Jupiter's
orbit
when the Hubble Space Telescope photographed it on March 11, 2014.
Hubble
resolves two jets of dust coming from the solid icy nucleus. These
persistent jets
were first seen in Hubble pictures taken on Oct. 29, 2013. The feature
should
allow astronomers to measure the direction of the nucleus's pole, and
hence,
rotation axis. The comet will make its closest approach to our Sun on
Oct. 25, 2014, at a distance of 130 million miles, well outside Earth's
orbit. On its inbound leg, Comet Siding Spring will pass within 84,000
miles of Mars on Oct. 19, 2014, which is less than half the Moon's
distance from Earth. The comet is
not expected to become bright enough to be seen by the naked eye.
About this Image:
[Left] This is a Hubble Space Telescope picture of comet C/2013 A1 Siding
Spring as observed on March 11, 2014. At that time the comet was 353
million miles from Earth. The solid icy nucleus is too small to be
resolved by Hubble, but it lies at the center of a dust cloud, called a
coma, that is roughly 12,000 miles across in this image.
[Right] When the glow of the coma is subtracted through image processing,
which incorporates a smooth model of the coma's light distribution,
Hubble resolves what appear to be two jets of dust coming off the
nucleus in opposite directions. This means that only portions of the
surface of the nucleus are presently active as they are warmed by
sunlight, say researchers. These jets were first seen in Hubble pictures
taken on Oct. 29, 2013. The feature should allow astronomers to
measure the direction of the nucleus's pole, and hence, rotation axis.
Discovered in January 2013 by Robert H. McNaught at Siding Spring
Observatory in New South Wales, Australia, the comet is falling toward
the Sun along a roughly 1-million-year orbit and is now within the
radius of Jupiter's orbit. The comet will make its closest approach to
our Sun on Oct. 25, at a distance of 130 million miles — well outside
Earth's orbit. On its inbound leg, Comet Siding Spring will pass within
84,000 miles of Mars on Oct. 19, 2014 (less than half the Moon's
distance from Earth). The comet is not expected to become bright enough
to be seen by the naked eye.
An earlier Hubble observation made on Jan. 21, 2014, caught the comet
as Earth was crossing the comet's orbital plane. This special geometry
allows astronomers to better determine the speed of the dust coming
off the nucleus. "This is critical information that we need to
determine how likely and how much the dust grains in the coma will
impact Mars and Mars spacecraft," said Jian-Yang Li of the Planetary
Science Institute in Tucson, Ariz.
This visible-light image was taken with Hubble's Wide Field Camera 3.
Source: HubbleSite
