SKYLIGHTS
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.
