We have two astronomical sights to view in this month's sky. One, a deep, partial lunar eclipse on the night of March 23, is the last lunar eclipse visible to us in the 1900's. The second sight, visible all month and into next month, is this spring's comet, Comet Hale-Bopp.
Moon is well up at 8:40 p.m. on March 23 when it begins moving into the penumbra of Earth's shadow, the outer part of our shadow in which Sun's light is not completely blocked by Earth. This penumbral phase is not noticeable at first but about 9:20 you may be able to detect a slight dimming of the lower left part of Moon as it moves deeper into the penumbra. At 9:57 Moon begins moving into the umbra of Earth's shadow, the dark inner portion in which all of Sun's light is blocked, as the partial phase of the eclipse begins.
Greatest eclipse occurs at 11:39 p.m. When the eclipse is at its maximum, with 93% of Moon's diameter inside Earth's umbra, you will be able to see only a curved sliver at the top that is still bright white. Look for a reddish or coppery glow to the portion of Moon that is in the umbra of Earth's shadow as the eclipse progresses.
Moon leaves Earth's umbra at 1:22 a.m. on the morning of March 24 and the eclipse officially ends at 2:38 a.m. when Moon leaves the penumbra of our shadow, but no dimming will be evident after 2 a.m.
About 10 degrees above and to the right of Moon during the eclipse will be Mars, three days past its least distance from us. The Red Planet will be brighter than Saturn was during last September's total lunar eclipse. And perhaps visible, if you have a clear, dark, northern horizon, will be the tail of Comet Hale-Bopp projecting up from the comet located about 3 degrees below the horizon.
Comet Hale-Bopp was discovered in 1995 beyond the orbit of Jupiter, farther away than any comet has ever been discovered. Its official name is C/1995 O1. Astronomers have learned that this comet has a nucleus larger than the nucleus of Comet Halley. It continues to brighten as it approaches Earth and Sun, and seems to be one of the brightest comets of this century.
It is currently visible about 20 degrees above the east-northeast horizon at the beginning of astronomical twilight. Before this twilight begins, about 1 ½ hours before sunrise, there is no sunlight in the sky. If you have a dark location you can easily make out its coma, or head, and its tail. Even if your sky is not too dark, it is still easy to find Hale-Bopp. It's big and looks nothing like any of the stars in that portion of the sky.
It is not likely that it will appear as large as did Hyakutake last spring. When closest on March 22, Hale-Bopp will be 1.315 astronomical units (more than 122 million miles) from Earth, about 13 times as far as Hyakutake was at its closest last March. And by March 22 Hale-Bopp will be visible in the west-northwest sky at the end of astronomical twilight, 1 ½ hours after sunset, as well as in the morning sky. By the time Hale-Bopp nears perihelion, about 10:15 p.m. on March 31, it will be visible only in the evening sky. It will be highest in the evening sky during the second week of April.
Comets sometimes develop spectacular dust tails after perihelion, so Hale-Bopp may be even brighter after passing within 0.914 astronomical units (about 85 million miles) of Sun at the end of March.
If you have a computer and access to the World Wide Web, you can view the altitudes and azimuths of Hale-Bopp at the beginnings and ends of astronomical twilight in Morgantown for each day in March and April. Open http://www.as.wvu.edu/~jel/comet to see where to look for this bright comet as well as to find links to other Web sites for Comet Hale-Bopp.
