SKYLIGHTS
Astronomy news for the week starting Friday, April 28, 2000.
The next Skylights will appear on Sunday, May 7. The crescent Moon
wanes toward new early in the week, the phase reached the night of
Wednesday, May 3. A day later, the evening Thursday May 4, the
slim waxing crescent will pass some 5 degrees south of Mars.
Though the Moon will be barely visible in bright twilight, Mars,
far away and relatively faint, will be very difficult to find.
While the crescent waxes, it passes perigee (its closest point to
the Earth) on Saturday, May 6.
The "ancient" planets, those known since humans have walked the
Earth, continue to gather together, Mars, Jupiter and Saturn still
to the east of the Sun, Mercury and Venus to the west of it. This
week all the ancient 7 "moving bodies" of the sky -- the Sun, Moon,
Mercury, Venus, Mars, Jupiter, and Saturn -- will be in their
closest congregation, a highly unusual occurrence, and one
unfortunately unobservable because of the brilliance of the Sun.
The Sun, of course, does not really move against the stellar
background, but only appears to do so because of the movement of
the Earth. With some exceptions in ancient Greece, the truth was
not understood until Copernicus "placed" the Sun at the center of
the Solar System.
The sky is brought to Earth in many ways. These seven bodies, plus
the seven days of the quartering of the Moon's phases, are
responsible for our 7-day week; the 29.5-day period of the lunar
phases (stretched a bit to fit the year) made our 30-31 day months;
and the 365-day year created the 360 degrees of the circle (360 a
wonderful number that can be divided by a host of others). As a
result, the Earth goes around the Sun almost one degree of its
orbit per day, the Sun appears to move along the ecliptic (its
apparent path) by almost one degree per day, and at night the stars
(if viewed at the same time) seem to slip to the west daily by the
same amount.
This week hosts one of the better meteor showers of the year, the
"Eta Aquarids." With the Moon out of the sky, an observer on the
morning of Friday, May 5, may witness as many as 30 meteors per
hour pouring from the constellation Aquarius. (The best place to
look, however, is overhead.) Meteors are caused by small
interplanetary rocks hitting and heating up in the Earth's
atmosphere. Almost all meteors come from the debris flaked from
comets as they disintegrate under the heat of the Sun. The Eta
Aquarids are seen as we pass near the orbit of Halley's Comet,
which tours the Sun every 76 years. In October, when we pass close
to the other side of the orbit, Halley's debris produces the
Orionid shower.
