|
Closeup of a Comet
This close-up view of the head of Comet Ikeya-Zhang
gives the impression that it is speeding through our sky.
Indeed, comets travel tens of thousands of miles
per hour as they pass close to the Sun, but at their large
distance from the Earth (70 million miles in this case), they appear
to move quite slowly through our sky
The color technique used to make this image is evident as a result of the
motion of the comet. The telescope remained pointed at the comet, which
moved slightly between the blue, red, and green filtered exposures. Thus the
background stars appear as short three-color streaks
The features of a comet head are the nucleus (the bright spot at lower right)
and coma (the more diffuse material surrounding the nucleus). The tail of
the comet points (generally) away from the Sun. Though they can extend for
many millions of miles, the entire comet has a mass comparable to a small
mountain. The nucleus is composed of rock and ice (a "dirty snowball") and
the tail contains nuclear material that has been vaporized by the heat and
light of the Sun.
|
|
|