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Annular eclipse

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 your patience.

The 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 from the 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.
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