Astronomy news for the week starting Friday, July 25, 2008.
Passing
last quarter during daylight (in North America) on Friday, July
25, the Moon begins to fade away as it enters its waning
crescent phase and heads towards new
on Friday, August 1, at which time it will totally
eclipse the Sun and present a fine sight for people in Europe
(Russia) and Asia (China), but not in North America. A partial
solar eclipse will be visible in extreme northern North America,
and will cover nearly all of Europe and Asia except for Spain,
Portugal, and Japan. (Paired with this eclipse will be a partial
lunar eclipse on August 16, which will be invisible in North
America as well.) Back to home, the last glimpse of the thin crescent will be the morning of
Thursday, July 31, in eastern twilight. Look next week for the waxing crescent in western evening twilight.
On Tuesday the 29th, the waning crescent goes through perigee,
bringing higher-than-usual tides to the
coasts.
Of the ancient planets, the only one now readily visible is
Jupiter, which is seen rising gloriously in the southeast in early
evening. Bright and beautiful, hard to miss,
Jupiter crosses the meridian to
the south around 11:30 PM Daylight. Its
retrograde, westerly, motion against the background stars has
returned it to a lovely position just to the northeast of the Little Milk Dipper in Sagittarius, the locally bright stars
making the planet's motion from week-to-week quite obvious. Of the
"missing" bright planets, only Mercury makes some sort of
news, as it passes superior conjunction with the Sun (on the other side of
the Sun) on Tuesday, the 29th. Saturn and Mars are
quite lost in evening twilight.
With the Moon nicely out of the way, we have a good chance to
witness one of the better meteor showers of the year, the Southern Delta
Aquarids, named after a southern star in Aquarius that marks the region of the sky from which
the meteors seem to come (which involves the direction of the
meteoroid stream about the Sun combined with the orbital motion of
the Earth). The shower is visible from late July into early August
with a broad peak around Monday, July 28, when under
a dark sky it will produce perhaps 20 meteors a minute. The best
time to look will be around 3 or 4 AM, to the south. The parent
comet, from which meteor showers derive (as the comets slough off
dust and rock), is unknown.
Summer is a fine time to catch the two celestial crowns. Look for a semi-
circle of stars, Corona Borealis,
the Northern Crown, to the northeast of bright Arcturus. Then if you have a good
southern horizon and don't live too far north, look directly
beneath the Little Milk Dipper of Sagittarius (now well-marked by
Jupiter) to find the more ragged semi-circle of Corona Australis, the Southern Crown.
