Mars-bound comet scores a galactic ‘ringer’

Comet C/2013 A1 Siding Spring passes the beautiful ring galaxy NGC 1291 in the constellation Eridanus the River on August 2, 2014. Credit: Damian Peach

Comet C/2013 A1 Siding Spring  has been gaining ground on the planet Mars with only 208 million miles separating the two as of today. Discovered in January 2013, astronomers quickly determined the comet would pass only 82,000 miles from the planet on October 19 this year.  That’s more than 10 times closer than any comet has ever been observed to pass by Earth.

Because of the possibility for stray dust particles from the comet’s tail to damage instruments on several of its orbiters, NASA recently initiated orbital maneuvers to place them out of harm’s way on the opposite side of the planet during the time of closest approach.

Meanwhile, observers in the southern hemisphere have been keeping watch on the comet through modest-sized telescopes as have astrophotographers like Damian Peach who shared this remarkably beautiful photo of C/2013 A1 passing by the peculiar galaxy NGC 1291 in Eridanus. No danger of those two ever brushing up against one another –  the galaxy’s about 33 million light years in the background.

When we’re near the orbital plane of a comet, we look across space nearly edge-on into the cloud of dust it sheds. From our perspective, the tails and dust collapse into a flattened streak with the comet’s core or nucleus near the center. An anti-tail is really a dust or gas tail, but it appears to precede the comet instead of trail it, hence the term ‘anti’. Credit: Justin J. McCollum

Two things to notice here – the comet’s peculiar stretched-out shape and the galaxy’s striking interior ring.

Earth recently crossed Siding Spring’s orbital plane, providing with a unique, nearly edge-on view of the comet. Tails as well as dust shed in the its path stack up to form a flattened ‘pancake’ comet for a few brief days or weeks. (see diagram).

Composite image of NGC 1291  from the Galaxy Evolution Explorer and data from the Cerro Tololo Inter-American Observatory in Chile shows brilliant, massive stars firing up inside the ring. Galaxy rings may also form when galaxies pull in material from their surroundings. Shocked and heated through compression, new stars form. Credit: NASA

A number of galaxies show rings but few as symmetrical as NGC 1291. It’s thought that ring galaxies form when another galaxy collides and passes straight through the host galaxy.

While stars rarely crash during such encounters, merging gas clouds and gravitational disruptions can spark waves of star formation. Images taken by NASA’s Galaxy Evolution Explorer ultraviolet telescope clearly shows a ring of massive, young blue stars.

Beauty can be so happenstance.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

2 thoughts on “Mars-bound comet scores a galactic ‘ringer’

  1. Can I send u a photo? My friend said he saw something fly out of the moon and he took a pictures of it. Its freaking me out too. Please help

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