SKYLIGHTS
Astronomy news for the week starting Friday, April 13, 2001.
Our Moon passes through third quarter this week on Sunday the 15th,
about the time of moonset. It then wanes through its crescent
towards new, that phase reached next week. While the crescent
begins to narrow in the early morning sky, the Moon passes north of
Neptune on Monday the 16th, then north of Uranus the following day.
Two days after the quarter, our companion passes apogee, where it
is farthest from the Earth.
The sky presents an interesting set of planetary pairings. The
outer four planets are often lumped together as "Jovian planets,"
as if they were of one kind. Jupiter and Saturn, however, the two
giants of the Solar System (which are quite similar to each other),
are very different from much smaller and more distant Uranus and
Neptune, which themselves are near-twins. The couples are also
currently paired in space. As the Sun sets and twilight ends, the
two evening planets find themselves ever closer to the horizon.
Both still in Taurus, Saturn now sets just after 10 PM daylight
time, Jupiter about an hour later. At the same time, both are
running ever faster toward the east against the stellar background.
Jupiter, the closer of the pair, is moving the faster, causing it
to pull away from Saturn. While the ringed planet will linger in
Taurus, Jupiter (which will pass north of Aldebaran on Monday the
16th) is heading toward Gemini. Uranus and Neptune are in much the
same configuration. Neptune rises around 3 AM (Daylight time),
Uranus an hour later. Both now in Capricornus and also moving
easterly, closer Uranus is pulling away from Neptune, and will soon
enter Aquarius on its 84-year journey around the Sun, leaving
distant Neptune behind. Uranus, faint but visible to the naked
eye, is now passing roughly north of Deneb Algedi (Delta
Capricorni), making it rather easy to find.
Not paired, but shining in solitary splendor, Venus rules the
eastern morning twilight sky. Our nearest neighbor has been in
retrograde motion, moving to the west against the stars. On
Tuesday the 17th it ceases retrograde and begins its direct
westerly motion once again, though at a slow pace, the planet
continuing to separate from the Sun and rising ever
earlier.
Directly to the south at 8 PM, between Gemini and Leo, lies the dim
constellation Cancer, the Crab. Its greatest distinction is a
small box of 4 stars within which lies a fuzzy patch, an open
cluster called the "Beehive." Not all that much farther than the
famed Pleiades in Taurus, the Beehive (a lovely sight in a small
telescope) is older and contains intrinsically less-luminous stars
and is therefore not so prominent.
