ISON, Mars, Regulus
From
NASA’s Astronomy Picture of the Day
In order top to bottom this
celestial snapshot features Comet ISON, planet Mars, and Regulus,
alpha star of the constellation Leo, in the same frame. The scene spans about 2
degrees near the eastern horizon in early morning skies of October 15.
Closest of the three,
the much heralded
Comet ISON (C/2012 S1) is by far the faintest at 14 light-minutes (1.7
AU) away. Mars is only slightly farther from our fair planet.
About 16.5 light minutes
(2 AU) away its normal ruddy
color is washed out in the exposure. Regulus outshines both comet and
planet from a distance of 75 light-years.
Just above Regulus, the
very faint smudge of light is actually the Leo I dwarf galaxy, 800,000
light-years away and almost lost in the glare of the bluish hued bright star.
Comet ISON is expected
to grow brighter, though. How
bright is still not clear, but not as bright as a Full Moon in night skies.
Estimated to be 1 to 4
kilometers in diameter, ISON's nucleus
might substantially survive its very close encounter with the Sun on
November 28. If so, the
comet will climb back above the eastern horizon in planet Earth's
northern hemisphere before
dawn in early December.
