C/2013 A1 Archives

Astrophotographer Damian Peach shares this spectacular image of comet C/2013 A1 Siding Spring approaching Mars taken just hours ago. The faint comet shows a small, condensed coma and bent tail against the glaring orange glow of the brilliant planet. Most photos of comets passing by a planet or deep sky object are lucky line-of-sight pairings with the comet in the foreground and object light years away in the background. Not this one. Both Siding Spring and Mars lie at nearly the identical distance from Earth of 151 million miles (243 million km).

Artist view of the comet passing closest to Mars this Sunday. At the time, the Mars orbiters from the U.S., Europe and India will be huddled on the opposite side of the planet to avoid possible impacts from comet dust. Credit: NASA — Artist view of the comet passing closest to Mars this afternoon October 19. At the time, the Mars orbiters from the U.S., Europe and India will be huddled on the opposite side of the planet to avoid possible impacts from comet dust. Credit: NASA

When closest to Mars this afternoon, Siding Spring is expected to shine at around magnitude -5 or about twice as bright as Venus. Mind you, that estimate considers the entire comet crunched down into a dot. But for those who remember, Comet Hale-Bopp remained at zero magnitude, 100 times fainter than Siding Spring, and made for one of the most impressive naked eye sights on spring evenings in 1997.

More recently, Comet McNaught climaxed at magnitude -5 in the daytime sky near the Sun in January 2007. It was plainly visible in binoculars and telescopes in a blue sky if you knew exactly where to look and took care to avoid the Sun. Would-be Martians are far more fortunate, with Siding Spring appearing high overhead in a dark sky from some locations, including that of NASA’s Curiosity Rover.

Comet C/2013 Siding Spring as it rises and sets over the Curiosity Rover this weekend October 18-19. Credit: Solarsystemscope.com

Right on time for today’s encounter, the folks at Solarsystemscope.com have rolled out an interactive simulation of Comet Siding Spring’s appearance in the sky above Curiosity. Just click the play button on the control panel above to run it live. Seen from Mars, the comet bobs along Eridanus the River southwest of Orion, passing high in the southern sky overnight. What a sight!

Another photo, just in, taken of the comet and Mars today by Rolando Ligustri. Beautiful!

The comet nucleus is only about 0.4 miles (700 meters) across, but the coma or atmosphere fluffs out to around 12,000 miles (19,300 km). Seen from the ground, Siding Spring would span about 8°of sky or 16 full Moons from head to tail. Moving at 1.5° per minute, we could watch crawl across the heavens in real time with the naked eye. Wish I zoom to Mars for a look, but the rovers and orbiters will be our eyes as they study and photograph the comet during its brief flyby. As soon as those pictures become available, we’ll publish them here. Can’t wait!

Come Siding Spring comes out the other side!

While we’re waiting, amateur astronomers have been busy shooting additional photos and creating videos from their images. Fritz Helmut Hemmerich made this video from 1200-meters at Tenerife in the Canary Islands showing Comet Siding Spring immediately after its Mars encounter. One thing we know for certain is that the comet is intact after its close brush.

Negative image showing Comet Siding Spring closely approaching Mars today. Credit: Peter Lake

And find our more amazing photos and information at Sen TV, and you can follow them on Twitter at @sen.

With excitement building as Comet Siding Spring rapidly approaches the Red Planet, we’ll soon have the opportunity to spot it through our own telescopes. Dark skies return this week with the moon now past full and rising later each night. Until recently, the comet could only be seen by skywatchers living in southern latitudes. Now it’s popped high enough above the southern horizon to see from mid-northern latitudes, albeit low in the sky. Observers with 8-inch (20 cm) or larger telescopes can follow the comet as it travels from Scorpius north to Ophiuchus and its encounter with Mars on October 19.

adsfdf — JPL Horizons light curve for Comet C/2013 A1 Siding Spring shows it brightening as it approaches Earth and then fading after late September. For our purposes we’re interested in the purple squares which are visual magnitude estimates of the whole comet submitted to the Comet Observation Database. Recently, the comet has faded faster than predictions. Click for more details. Credit: CIOC

Until late September, the comet had been brightening as forecast based on the simple principle that the closer an object is to Earth the brighter it appears in the sky. Siding Spring came just shy of 1 A.U. of Earth in early September and has since been slip-sliding away. All through the first weeks of September it glowed at magnitude +9-10 and could be spotted in small telescopes trekking across the south polar constellations. Now on the cusp of its big moment with Mars, Siding Spring has been fading faster than expected.

It could be running low on exposed ice or concluding a long, slow outburst. Maybe it’s as simple as our changing perspective on the comet’s tail – we see it from the side now instead of looking down the tail where reflective dust piles up along our line of sight. No one knows exactly why, but given that comets are famous for their unpredictability due to their fragile nature and the varying rates at which they sputter away ice and dust, we shouldn’t be too surprised.

The paths of Mars and Comet Siding Spring are clearly on a (near) collision course! Watch over the coming nights as they draw ever closer. Source: Chris Marriott's SkyMap — The paths of Mars and Comet Siding Spring are clearly on a (near) collision course! Watch over the coming nights as they draw ever closer. This map shows the sky facing southwest at nightfall from Kansas City, Missouri. From the central U.S. the comet will be about 13-15º high but only ~5-8º altitude in the northern border states. Source: Chris Marriott’s SkyMap

So what does that mean for observers? The most recent observations put the comet at about magnitude +11 with a loosely condensed coma and diameter of about one arc minute or a little larger than Jupiter appears in a telescope. It’s a small, relatively faint object now but should be visible in 8-inch and larger telescopes from a dark sky assuming it doesn’t “drop off the deep end” and fade even faster. With Mars nearby, finding the general location of Siding Spring is easy. The maps will help you pinpoint it.

Daily positions of Comet Siding Spring October 10-20 from the central U.S. at nightfall. Stars shown to magnitude +11.5. Closest approach to Mars is October 19. Brighter stars like 3 Sagittarii, 44 and 51 Ophiuchi and Theta Ophiuchi are labeled. Source: Chris Marriott's SkyMap — Daily positions of Comet Siding Spring October 10-20 from the central U.S. at nightfall. Stars shown to magnitude +11.5. Closest approach to Mars is October 19. The brighter stars 3 Sagittarii, 44 and 51 Ophiuchi and Theta Ophiuchi are labeled. Click for large version to print and use at the telescope. Source: Chris Marriott’s SkyMap

The good news is that the comet is heading straight north and getting higher in the sky every night. The bad news is that it’s also dropping westward each evening mostly negating its northerly altitude gains. Those in the southern U.S. will have the best viewing window with Siding Spring 20º high at nightfall (14º in the central states and 6º in the north). To ensure success, find a spot with a wide open view as far down to the southwestern horizon as possible. You’ll make best use of your time and see the comet highest if you set up during evening twilight and begin searching as soon as the sky is dark. Given that Mars is 1st magnitude and the comet has faded more than expected, it may be difficult to see against the planet’s glare on the 19th. Not that I want to dissuade you from trying, but the nights leading up to and after the encounter will prove better for comet spotting.

Need to get in closer yet? This map shows Mars and Comet Siding Spring on five nights closer to its flyby with stars to magnitude +12. Time and location are the same as the map above. Click for larger version. Source: Chris Marriott's SkyMap — Need to get in closer? This more detailed map shows Mars and Comet Siding Spring nightly October 15-20 with stars to magnitude +12. Time and location are the same as the map above. Click for larger version. Source: Chris Marriott’s SkyMap

The fluffball passed the glittery Butterfly Cluster (M6) in Scorpius on October 9 displaying an attractive curved tail pointing southeast. Tim Reyes of Universe Today calculated the current tail length at ~621,000 miles (1 million km) with a coma ~19,900 miles across (32,000 km). Closest approach occurs around 1:28 p.m. Central Daylight Time (18:28 UT) October 19 when the comet will miss Mars by only 88,000 miles (141,600 km). Dust particles leaving the coma will rip by the planet at ~125,000 mph (56 km/sec). Will they pass close enough to set the Martian sky a-sparkle with meteors?

Not only will the Mars orbiters gather information about the comet and its dust before, during and after the encounter, a fleet of additional telescopes will be making the most of the rare opportunity. Credit: NASA — Not only will the Mars orbiters gather information about the comet and its dust before, during and after the encounter, a fleet of additional telescopes will make the most of the rare opportunity. Credit: NASA

According to a recent NASA press release, the period of greatest risk to orbiting spacecraft will start about 90 minutes after the closest approach of the comet’s nucleus and will last about 20 minutes, when Mars will come closest to the center of the widening trail of dust flying from the comet’s nucleus. Since the comet will barely graze the planet, dust impacts on orbiting spacecraft may or may not happen.

Back on Earth we can watch the daredevil pass by telescope or catch it live on the Web here:

* SLOOH: broadcast begins Sunday Oct. 19 at 9:51 a.m. CDT (14:51 UT)

* Gianluca Masi’s Virtual Telescope: streaming begins Sunday, Oct. 19 at 11:45 a.m. CDT (16:45 UT)

Tag: C/2013 A1

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