Astronomy news for the week starting Friday, June 10, 2001.
The Moon, beginning the week in its waning gibbous phase, passes
third quarter the evening of Wednesday, the 13th, and thereafter
wanes through crescent, every day rising later after midnight. It
passes south of Neptune, in Capricornus, on Sunday the 10th, and
south of Uranus, in the far eastern end of the same constellation,
the following day.
The two planets outward from the Earth provide a wonderful
contrast. Jupiter, the Solar System's giant, and ordinarily the
second brightest of planets, passes conjunction with the Sun on
Thursday the 14th, and will be quite invisible. Mars, on the other
hand, is now at its best, passing opposition to the Sun the day
before, Wednesday, the 13th. On opposition night, Mars will rise
at sunset, set at sunrise, cross the celestial meridian to the
south at midnight (1 AM daylight time), and have its greatest
angular retrograde (westerly) speed. It will also about as close
to the Earth as possible during this orbital round, 68.6 million
kilometers, or 42.6 million miles. Unfortunately, the red planet,
which now shines brighter than any star in the sky (and is now
exceeded only by the morning's Venus, the Moon, and the Sun), will
also be at about its most southerly position (just to the west of
Sagittarius), and for northern observers about as low as it can
get. Turbulence in the Earth's atmosphere then makes detail more
difficult to view by telescope. After opposition, Mars will begin
to rise before sunset, will move more and more into the early
evening sky, and will be with nicely us for the remainder of the
year. Mars passes opposition to the Sun every 780 days. The orbit
is so eccentric that opposition distance vary considerably. The
next one will be better. The minimum distance is 56 million
kilometers (35 million miles), the maximum almost twice as great.
Only Venus comes closer.
Mars actually lies in far southern Ophiuchus between Sagittarius
and Scorpius, providing a good chance to compare the color of the
planet with its namesake Antares (Ares the Greek version of the war
god). As spring slowly blends into summer, these beautiful
summertime constellations, which contain the Milky Way, will begin
to overtake the more drab spring skies, which now still dominate in
the early evening, Virgo and Spica nearly due south as night falls.
Watch as they slip away a degree per day to the west as the sky
reflects the degree-per-day motion of the Earth around the Sun. If
your skies are dark, you might make out the dim box of stars that
forms Libra, the scales, the zodiacal constellation that lies
between Virgo and Scorpius.