2006-10-06 14:23:46 · 2 answers · asked by kjvonski 1 in Science & Mathematics ➔ Astronomy & Space
Because these are not well defined objects with sharp boundaries. Like a cloud which looks sharply delimited from the ground. But for an airplane pilot there's no definite location to pinpoint the start of the cloud. The "cloud density" increases continuously from zero well outside the cloud to the point where you are definitely within the cloud.
2006-10-06 14:58:28 · answer #1 · answered by bluecloud23 2 · 0⤊ 0⤋
The underlying mass distribution of a gravitationally bound system is reflected in its kinematics. In the edge-on spiral galaxy NGC 891, hot X-ray emitting gas is seen in the halo, beyond the disk-confined stars and cold gas. In using CX to measure the rotational velocity, in addition to the temperature and density distribution of the hot gas, we can determine the shape of the underlying dark-matter distribution in three dimensions as compared with the two dimensions accessible to studies using the stars and cold gas.
2006-10-07 02:38:02 · answer #2 · answered by veerabhadrasarma m 7 · 0⤊ 0⤋