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.
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