Natural History Magazine

Skylog

July-August 2008

By Joe Rao

Total solar eclipse, August 1: The moon’s umbra, or full shadow, will sweep from Canada into China (thin black path); neighboring regions will experience a partial eclipse (purple shading). Earth’s night side is shown for the beginning of the eclipse; dotted line shows where it will be two hours later, when the eclipse ends.

The “star” of the summer is Jupiter, shining bright within Sagittarius, the Archer—above and to the left of the constellation’s most prominent star pattern, popularly known as the Teapot. In early July, when Jupiter swings into opposition (that is, when it’s on the opposite side of the Earth from the Sun), the planet rises at sunset, ascends highest in the south around 1 a.m. local daylight time, and sets at sunrise. Later in July and throughout August, it will be prominent in the southeast as dusk fades and will remain visible for most of the night.

The first total solar eclipse in nearly two and a half years takes place the morning of August 1. The Moon’s umbra, or full shadow, will first fall north of the Arctic Circle in Canada, where Earthlings positioned to get the earliest view of totality will see the Sun eclipsed as it rises. The umbra will then sweep northeastward, giving a glancing blow to northern Greenland, before heading southeast out of the Arctic Circle, through Siberia and western Mongolia and into China. Viewers about 400 miles southwest of Beijing will get the last glimpses of the total eclipse as the Sun sets. Many eclipse watchers are expected to gather at Novosibirsk, the largest city in Siberia. Weather permitting, they will witness a total eclipse lasting two minutes twenty seconds. Many regions will experience a partial eclipse.

The Perseid meteor shower, which peaks during the night of August 11–12, will probably offer the best meteor spectacle in 2008, since the December Geminids will be washed out by a full Moon. The waxing gibbous Moon will set around 1:30 a.m. local daylight time, leaving a dark sky for the next three hours. The constellation Perseus, from where these shooting stars appear to radiate, will be climbing the east-northeastern sky during the predawn hours.

The Perseids appear each summer as Earth crosses the orbit of comet Swift-Tuttle, brushing past dusty debris the comet has left in its wake. Following a long elliptical path, the comet shows up in our neck of the solar system about every 130 years. Although its most recent visit was in 1992, most of the meteors we see result from debris the comet left behind hundreds or even thousands of years ago. The Perseids peak over just a few hours; this year viewers in the Pacific time zone who scan the sky after the Moon sets may enjoy the best show. However, the shower remains substantial for about three days.

Joe Rao is a broadcast meteorologist and an associate and lecturer at the Hayden Planetar- ium in New York City.

JULY NIGHTS OUT

1 Mercury approaches its greatest elongation (apparent distance) west of the Sun—a separation of 22 degrees. Look for the planet low near the east-northeast horizon about an hour before sunrise. An hour or so after sundown this same day, low in the western sky, yellow-orange Mars will appear to hover just above the bluish star Regulus. Though equally bright, they are easily distinguished through binoculars. To the upper left of the pair, golden and twice as bright, is Saturn.

2 The Moon becomes new at 10:19 p.m. eastern daylight time (EDT).

5 Low in the western sky, about an hour after sundown, a crescent Moon, the bright star Regulus, and the planets Mars and Saturn form a straight line from lower right to upper left.

9 Jupiter arrives at opposition to the Sun (see story above).

9–11 The faster-moving Mars—situated about 1 degree below Saturn on the 9th—passes noticeably to Saturn’s left by the 11th.

10 The Moon waxes to first quarter at 12:35 a.m. EDT.

18 The Moon becomes full at 3:59 a.m. EDT.

25 The Moon wanes to last quarter at 2:42 p.m. EDT.

AUGUST NIGHTS OUT

1 A total solar eclipse sweeps from northern Canada across the Arctic Circle and Siberia into China (see story above). The Moon becomes new at 6:12 a.m. EDT.

8 The Moon waxes to first quarter at 4:20 p.m. EDT.

11–12 The Perseid meteor shower peaks (see story above).

15 The planets Mercury, Saturn, and Venus will be closely bunched together close to the western horizon just after sunset. Unfortunately, only Venus may stand out against the Sun’s glow—but viewers with binoculars could luck out.

16 The Moon becomes full at 5:16 p.m. EDT. A partial lunar eclipse will favor much of Europe, Africa, and Asia beginning at 19:36 and ending at 22:44 Greenwich Mean Time.

23 The Moon wanes to last quarter at 7:49 p.m. EDT.

30 The second new Moon this month arrives at 3:58 p.m. EDT.