Photo of the Week. On May 10, 1994, the new Moon
glided across the Sun, but too far away from Earth to cover it
completely, the result an "annular eclipse" that is "read" from
right to left. Images and panel by Mark Killion.
Astronomy news for the week starting Friday, July 20, 2007.
Skylights now resumes its normal weekly schedule. Thanks again for
Moon starts us off as a fat waxing
crescent that almost immediately, on Saturday, July 21, passes
its first quarter (near Moonset in North
America), and then for the rest of the week, glides through its waxing gibbous phase (not reaching full until Sunday the 29th). The night of
Tuesday the 24th, it will pass by the head of Scorpius and will be seen down and to the right of
Jupiter (and to the immediate right of Antares), while the following night
it will be down and to the left of the planet, the star Antares now
to the right of a line between the two. Three hours after the
formal quarter, the Moon passes apogee,
where it is farthest from
Earth. With the Earth also not far from aphelion (farthest
Sun), tidal ranges
(high-to-low tide) along the coasts will be at a minimum.
Having passed its greatest brilliancy, Venus is now in a serious descent (as seen night after
night) toward the western horizon, and sets in mid-twilight. For
the past many months it has been moving along with the Sun to the
east against the background stars. On Wednesday the 25th, as it
prepares to swing between the Earth and the Sun, it reverses
direction and enters its brief
retrograde period, in which it moves to the west against the
background. On the other side of the sky, though, Mercury, the other "inferior planet" (so called because
Venus and Mercury are closer to the Sun than we are), makes a nice
appearance in eastern dawn, passing greatest western elongation as
the week begins.
Saturn sets about the same time as Venus, though its relative
faintness precludes observation. Time then to turn to Jupiter.
Low in the south at mid-evening-twilight, the planet lords it over
the rest of the sky until it sets around 2 AM Daylight Time. An
hour before the giant planet departs,
Mars rises. Look for it to the southwest of Taurus's Pleiades star cluster.
We get hit by a minor
meteor shower this week, the "Delta Aquarids" that peak July
28-29. The few meteors (in the morning about 10 an hour) will be
pretty much wiped out by the bright Moon.
The summer constellations are
on full display. Look for Scorpius (marked nicely by Jupiter) to
the west of south as the sky darkens, then over to the east a bit
to find Sagittarius, which is
marked well by the upside-down Little Milk Dipper. Were the Moon
not so bright, the Milky Way
would be glorious in a dark sky. Lesser known, since it is rather
far south, is the constellation to the southwest of Scorpius, Lupus (the Wolf), which sparkles with
hosts of bright blue stars.