SKYLIGHTS
Astronomy news for the week starting Friday, February 5, 1999.
The Moon passes through its third quarter this week on Monday, the
8th, just about sunrise. The third quarter, 90 degrees behind the
Sun, is high to the south in the light of the new day, a lovely
time to appreciate the quartering of the orbit when the day-night
division on the Moon exactly halves the lunar disk. On the night
of the Saturday the 6th, the waning gibbous Moon will rise just to
the northeast of Mars, the two making a fine sight in the sky after
midnight, the bright star Spica to the west of them.
But first admire Venus, now moving ever higher into western
twilight after sunset, so brilliant against the still-light sky
that it cannot be missed. Up and to the left of Venus, find bright
Jupiter. Since Venus is getting higher in the sky, and Jupiter
lower, the two are closing in on each other for a close conjunction
on February 23, the next couple of weeks providing a great
opportunity to see planetary motion in quick action. Take the kids
out to watch! Saturn then shines to the left of Jupiter, the three
planets nicely outlining the ecliptic, the apparent path of the
Sun.
The biggest news is of dim Pluto. The "last planet" of the Solar
System, Pluto averages 40 Earth-Sun distances from the Sun, the
next one in, Neptune, 30. But Pluto's orbit is oddly eccentric,
allowing it to come closer to the Sun than Neptune for a brief
portion of its orbital period. (The two cannot collide). At about
4 PM Central Time on January 21, 1979, Pluto moved closer to the
Sun than Neptune, and for the past 20 years has been the "eighth"
planet rather than the "ninth." That status will end on Thursday
the 11th at 4:09 AM Central Time, when Pluto moves out farther than
Neptune, where it will stay for the next 230 years. Pluto's odd
orbit and small size are part of the reason for the discussion
about Pluto's argued demotion from "planet" status to something
else, to the largest of a huge number of "trans-Neptunian" bodies,
60 or so of which are now known.
