Daily Suspicious0bserver's Weather Post:
October 17, 2014
What's in the sky tonight?
October 17, 2014
-Before dawn Saturday morning, Jupiter shines above the waning Moon, as shown at right. Although they look rather close together, Jupiter is 2,100 times farther in the background — it's at a distance of 47 light-minutes, compared to the Moon's 1.3 light-seconds.
-On Sunday, Oct. 19th, Comet Siding Spring will pass only 140,000 km away from Mars. For comparison, that's about 1/3rd the distance between Earth and the Moon. For a while last year, astronomers thought the comet might actually hit Mars, setting off a cataclysmic climate change experiment, but now we know it's going to be a near miss. Last night, only three days before closest approach, astrophotographer Damian Peach snapped this picture. "The comet is presently moving against the dense star clouds of the southern Milky Way," says Peach. "Soon, however, it will reach Mars."
An international fleet of Mars orbiters and rovers will observe the encounter from close range. The most interesting data could come from MAVEN, a NASA spacecraft that has reached Mars just ahead of the comet. MAVEN is designed to study the martian atmosphere. That's good, because when the comet arrives, the atmosphere of the comet will likely brush against the atmosphere of Mars, possibly sparking auroras on the Red Planet. MAVEN could record these alien lights.
"Just as exciting," adds comet researcher Karl Battams of the Naval Research Lab, "is the prospect of the Mars Reconnaissance Orbiter's HiRISE camera being able to actually resolve (i.e. determine the shape of) the nucleus of the comet. ESA and NASA spacecraft have seen comet nuclei before, but comet Siding Spring is a little different. It's an 'Oort Cloud comet' on its first ever foray into our solar system. This means it is largely pristine and will likely not have undergone any major changes since it formed. We've never seen one of these comets up close. Never. We don't know exactly what to expect."
Experienced amateur astronomers with mid-sized telescopes and sensitive digital cameras should have no trouble photographing Comet Siding Spring in the nights ahead. It can be found glowing like a 12th magnitude star in the constellation Ophiuchus right next to ... you guessed it ... the planet Mars.
Astro Picture of the Day:
October 17, 2014
Source:
This looks like a near miss but the greenish coma and tail of Comet Siding Spring (C/2013 A1) are really 2,000 light-years or so away from the stars of open cluster Messier 6. They do appear close together though, along the same line-of-sight in this gorgeous October 9th skyscape toward the constellation Scorpius. Still, on Sunday, October 19th this comet really will be involved in a near miss, passing within only 139,500 kilometers of planet Mars. That's about 10 times closer than any known comet flyby of planet Earth, and nearly one third the Earth-Moon distance. While an impact with the nucleus is not a threat the comet's dust, moving with a speed of about 56 kilometers per second relative to the Red Planet, and outskirts of its gaseous coma could interact with the thin Martian atmosphere. Of course, the comet's close encounter will be followed intently by spacecraft in Martian orbit and rovers on the surface.