Sunday, July 01, 2007
One degree of separation
Last night Saturn appeared to be directly above Venus. Tonight Saturn appears to be at the 2:00 position with respect to Venus. In reality this apparent motion is caused by the relative positions of Earth, Venus, and Saturn as all three swing around the Sun. Venus is closer to the Sun than Earth, so it is moving more quickly than Earth (see Kepler's Laws of Planetary Motion), but we are also seeing it from a different position in our own orbit each night. Saturn, farthest of the three from the Sun (beyond the orbits of Mars, the Asteroid Belt, and Jupiter), moves at a much more stately pace, taking nearly 29.5 years to make one trip around the Sun; much of its apparent motion is actually just an effect of viewing Saturn from the fast-moving platform of Earth.
Anyway. My point, as I stated a few posts ago, is that the visual separation of Saturn and Venus tonight is about one degree. So if you've seen this, now you know what one degree of separation looks like.
(Image above contrast- and brightness-enhanced to improve visibility. The unhealthy greenish glow of the houses across the street is caused by a Mercury vapor corner streetlight.)