Hubble: Comet Siding Spring

[orin stepanek]

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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.

Object Name: C/2013 A1 Siding Spring

Image Type: Astronomical/Annotated


Credit: NASA, ESA, and J.-Y. Li (Planetary Science Institute)


NEWS RELEASE IMAGES

[geckzilla]

Where's the link to the original article, Orin?

[bystander]

http://hubblesite.org/news/2014/19

[orin stepanek]

http://hubblesite.org/news/2014/19

Thanks; by!

[BDanielMayfield]

I first read about this comet and its coming encounter with Mars on Oct. 19, 2014 a little over a year ago:

http://www.skyandtelescope.com/communit ... 06441.html

Comparing early reports to the new makes it seem that the comet is likely to pass even closer to Mars than what was originally thought, although even a year ago orbital predictions where coming up with non-zero likelihoods of the comet actually impacting Mars. Has an impact possibility been ruled out?

When the news came out I had also asked about the possibility of a near miss with Mars causing a breakup of the comet, like the one that happened to Shoemaker-Levi 9. Has this possibility been ruled out?

Bruce

[Chris Peterson]

Comparing early reports to the new makes it seem that the comet is likely to pass even closer to Mars than what was originally thought, although even a year ago orbital predictions where coming up with non-zero likelihoods of the comet actually impacting Mars. Has an impact possibility been ruled out?

Yes. (Or to be more precise, while the odds are non-zero, they are so near zero as to not be worth significant consideration.)

When the news came out I had also asked about the possibility of a near miss with Mars causing a breakup of the comet, like the one that happened to Shoemaker-Levi 9. Has this possibility been ruled out?

It can't be, because it depends on the unknown nature of the nucleus. But it's probably pretty unlikely.

[MargaritaMc]

I first read about this comet and its coming encounter with Mars on Oct. 19, 2014 a little over a year ago:

Bruce

Gosh, Bruce! You're a time traveller!
M

[neufer]

When the news came out I had also asked about the possibility of a near miss with Mars causing a breakup of the comet, like the one that happened to Shoemaker-Levi 9. Has this possibility been ruled out?

It can't be, because it depends on the unknown nature of the nucleus. But it's probably pretty unlikely.

<<Comet Siding Spring will pass extremely close to Mars on 19 October 2014 at 18:30 UTC, so close that the coma may envelop Mars. It will pass Mars at a relative velocity of 56 km/s. The nominal pass is 135,000 km from the center-point of Mars and the uncertainty region shows that it will not come closer than 130,000 km.>>

• The Roche limit for tidal disruption from a Martian close encounter is:
  8,300 km for a rigid body & 16,100 km for a deformable (fluid like) body.

<<Phobos is the larger and closer of the two natural satellites of Mars. A small, irregularly shaped object with a mean radius of 11 km. Phobos orbits 9,376 km from the Martian surface, closer to its primary than any other known planetary moon. Due to tidal interactions, Phobos is drawing closer to Mars by one meter every century, and it is predicted that in 50 million years it will collide with the planet or break up into a planetary ring.>>

[BDanielMayfield]

I first read about this comet and its coming encounter with Mars on Oct. 19, 2014 a little over a year ago:

Bruce

Gosh, Bruce! You're a time traveller!
M

Ha ha. No, no more so than all of us, traveling through time second by second, always in the forward direction.

[BDanielMayfield]

Thanks for those answers Chris and Art.

Bruce