SKYLIGHTS

Astronomy news for the week starting Friday, November 24, 2000.

The week begins with the Moon out of sight, as it passes its new phase on Saturday, the 25th, just about the time of sunset in North America. Those with clear western horizons may get a glimpse in evening twilight of an extremely narrow crescent the night of Sunday the 26th, the Moon just beyond the limit at which it is visible. By the night of Monday, the 27th, it will be more easily seen. Two days later, the night of Wednesday, the 29th, the growing crescent (its nighttime side illuminated by "earthlight) will make a classic close pass to Venus, the Moon seen just a bit up and to the right of the brilliant "evening star," the second planet out from the Sun and by far the brightest of them all. The crescent Moon will end the week at apogee, when it is farthest from the Earth, on Thursday, the 30th, as it passes just above Neptune.

Last week, Saturn passed opposition with the Sun, and now it is Jupiter's turn. This planet, usually the second brightest in the sky (it can briefly be exceeded by Mars at the time of closest approach), passes opposition with the Sun the night of Monday, the 27th, at which time it will rise at sunset, set at sunrise, and be up all night. Look for it to the east just after sundown, nestled against the stars of Taurus. Saturn, the last of the "ancient planets" (those known since antiquity), will be up and to the right of the Solar System's giant. Since both Jupiter and Saturn are now in retrograde (backward, westerly) motion against the stars, and since Jupiter is closer to us than Saturn and thereby moving faster, the two for a time will draw a bit closer. But the attempt at togetherness is temporary, as once direct motion resumes next year, Jupiter will move quickly away from Saturn, passing into Cancer, while Saturn will linger in Taurus.

The stars of the Perseus myth now dominate the early evening, the Great Square of Pegasus high to the south around 7 PM. Stretching up and to the left of the Great Square's upper left star is Andromeda, which hosts near its center an obvious fuzzy patch of light, the great Andromeda Nebula (M 31), a spiral galaxy much like our own. At a distance of 2.4 million light years, M 31 is the farthest thing that can generally be seen with the unaided human eye. Its only rival is a smaller spiral galaxy in the nearby constellation Triangulum, M 33, which is 2.2 million light years distant and which can just barely be discerned without a telescope. (The "M" stands for Charles Messier, who in the 18th century catalogued some of the sky's brighter clusters and nebulae). In the opposite direction, down and to the left of the Square, try to find the dim distorted rectangle that represents the much more obscure constellation, Equuleus, the Little Horse.