Astronomy news for the week starting Friday, February 11, 2000.

The Moon passes its first quarter early in the week, on Saturday the 12th, just to the west of the Hyades of Taurus and down and southwest of the Pleiades. The night before, it can be found just three degrees south of Saturn. The Moon will then spend the rest of the week waxing toward full. The night of Tuesday the 15th it will make a fine sight as it comes to its most northerly position for the month within the bright stars of Gemini. The following night it passes perigee, when it is closest to the Earth.

Though brighter planets roam the sky -- Jupiter high to the southwest at dusk, Venus still visible to the southeast in early dawn -- the week belongs to little Mercury. This closest planet to the Sun will come to its greatest eastern elongation relative to the Sun, when it as far in angle east of the Sun as possible, on Valentine's Day, the night of Monday the 14th. Though Mercury is still only 18 degrees to the east of the Sun, the evening's ecliptic (which the planets closely follow) is now tilted at a high pitch to the horizon, which means the planet will be well-placed for viewing. Look in twilight near the southwestern horizon. Binoculars will help. Mercury is actually quite bright, and this week would rank as the third brightest "star" in the sky, after Sirius and Canopus. Twilight, however, does it in, making it rather difficult to find. The planet's proximity to the Sun and its poor viewing position make it difficult to see any surface features. Not until Mariner 10 passed it in 1974 did we know it was, like the Moon, very heavily cratered, its surface very old and terribly damaged by the bombardment of leftover debris after the formation of the Solar System 4.5 billion years ago. We have not been back since, and Mercury still remains something of a mystery, only 45% of it seen close up. Curiously, this smallest of terrestrial planets (those out to Mars) has, relative to its total bulk, the largest iron core.

Look overhead at 8 PM or so to find the underappreciated constellation Auriga, the Charioteer. Home to the sixth brightest star in the Sky, Capella (the "she-goat"), Auriga is filled with celestial sights, including some lovely telescopic clusters. Just to the southeast of Capella is a small triangle of fascinating stars, Capella's "Kids." The faintest of them ("Zeta," at the southwest apex) is a double whose large dim component eclipses the brighter every 972 days. The brightest ("Epsilon," at the northern apex) is one of the sky's stranger. Something (probably a cloud of dust with stars buried in it) orbits and eclipses a huge supergiant star every 27 years, the eclipse lasting for an amazing 714 days.
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