SKYLIGHTS
Astronomy news for the week starting Friday, April 23,
1999.
This week's Skylights is late because of the death of my beloved
father-in-law, Tibor Grossman, to whom it is dedicated.
The Moon's phases are now running close to a Friday cycle, as it
passed first quarter last Thursday (April 22) and will reach full
next Friday the 30th. The Moon's phase cycle is 29.5 days long,
not quite a month, so each quartering takes just a bit over a week,
the Moon -- one of nature's clocks -- responsible for both these
calendar periods. As the Moon waxes through gibbous, it will
encounter the bright star Regulus in Leo, appearing to the west of
the star the night of Friday the 23rd, and much closer to the east
of it the night of Saturday, the 24th. As it did to Aldebaran last
week, the Moon will occult Regulus on Saturday the 24th, but
unfortunately for North America in daylight around 4 PM Central
Time. Later in the week, the night of Thursday the 29th, the Moon
will appear a few degrees to the northeast of bright Mars.
The red planet makes its big splash this week, as it passes
opposition to the Sun on Saturday the 24th, when it will rise at
sunset, set at sunrise, and cross to the south at midnight. It is
also now moving near its greatest angular speed in retrograde --
backward or westerly -- motion (within the constellation Virgo), as
the Earth passes between it and the Sun. Since the full Moon
takes place after Martian opposition, the Moon encounters Mars just
before the Moon reaches its full phase. Because of the
eccentricity of Mars's orbit, the smallest distance between the
planets will not take place until Saturday, May 1, when Mars will
be 0.578 astronomical units (the average distance between the Earth
and the Sun), or a distance of 86.5 million kilometers, away from
us. As a result of the eccesntricity, the distance at opposition
varies considerably over a 17 year period. The minimum, near 56
million kilometers, will take place in this cycle at the opposition
of 2005.
At the beginning of April, Jupiter passed conjunction with the Sun,
and now it is Saturn's turn, the ringed planet aligned with the Sun
and quite invisible on Tuesday, the 27th. Watch now for Jupiter
just clearing the horizon in early dawn. Saturn will follow in
mid-May.
The spring stars are now in full flower. Look for the box that
makes Corvus the Crow down and to the right of Spica in Virgo, and
for lonely Alphard in Hydra, the Water Serpent, down and to the
right of Regulus in Leo.
