Monday, July 15 The First Quarter Moon hangs fairly low in the - TopicsExpress

Monday, July 15 The First Quarter Moon hangs fairly low in the southwestern sky as darkness falls this evening. The half-lit orb then sinks steadily toward the western horizon, where it sets just past midnight local daylight time. Our satellite officially reaches First Quarter phase at 11:18 p.m. EDT. The Moon lies in central Virgo, less than 1° (two Moon-widths) from 1st-magnitude Spica. For people in the Hawaiian Islands, Central America, and northwestern South America, the Moon occults (passes directly in front of) the bright star. Tuesday, July 16 The Moon moves approximately 12° relative to the background stars each day. That rapid motion carries it from near Spica yesterday evening to the vicinity of Saturn tonight. You can spy the ringed planet 3° north (to the upper right) of our satellite, which appears 60 percent lit this evening. You can use brilliant Jupiter as a guide to Mars all this week. This morning, the Red Planet stands 3° above and a bit to the right of its planetary sibling. At magnitude 1.6, Mars appears 25 times dimmer than its neighbor. If you look carefully through binoculars either today or tomorrow morning, you might see the open star cluster M35 just north of Mars. Unfortunately, the objects’ low altitude and the advancing twilight make this conjunction difficult to see. Wednesday, July 17 Comet PANSTARRS (C/2011 L4) should glow around 11th magnitude this week, so you’ll need a good-sized telescope to follow its trek back into the outer solar system. Fortunately, it remains on view all night for observers in the Northern Hemisphere. Tonight, the comet lies in the same field of view with the 11th-magnitude spiral galaxy NGC 5678. Magnifications of 100x or more will provide a dark background and good contrast to let you compare the objects’ shapes and structures. Tenth-magnitude Hebe arcs in front of the Serpent during July, ending the month 1° west of 4th-magnitude Mu (μ) Serpentis. // Astronomy: Roen Kelly Thursday, July 18 The 10th-magnitude asteroid 6 Hebe remains among the background stars of Serpens the Serpent this week, a short star-hop from magnitude 3.5 Mu (μ) Serpentis. Using a 4-inch or larger scope and a low-power eyepiece, start at Mu and then slide about 2° north-northwest to the 5th-magnitude star 25 Ser. Tonight, Hebe lies 0.5° due west of this star. To confirm a sighting, make a quick sketch of the star pattern and return to the same field a night or two later. The dot that moved is the asteroid. Friday, July 19 Brilliant Venus lies low in the west shortly after sunset all week. Shining at magnitude –3.9, the planet appears conspicuous as darkness falls to anyone with a clear sky and an unobstructed horizon. It stands approximately 10° above the horizon 30 minutes after the Sun sets. If you turn a telescope on Venus, you’ll see a disk that spans 12" and appears about 85 percent lit. Saturday, July 20 Perhaps no month better epitomizes summer in the Northern Hemisphere than July. And this month finds the season’s namesake asterism, the Summer Triangle, on prominent display. The trio’s brightest member, Vega in the constellation Lyra the Harp, stands nearly overhead shortly before midnight. The asterism’s second-brightest star, Altair in Aquila the Eagle, then lies more than halfway from the southeastern horizon to the zenith. Deneb, the luminary of Cygnus the Swan, marks the Summer Triangle’s third corner. Although it is this asterism’s dimmest star, it’s the brightest point of light in the northeastern sky. Brilliant Venus joins 1st-magnitude Regulus as darkness falls July 21, in the first of two pretty conjunctions in one night. // Astronomy: Roen Kelly Sunday, July 21 Venus meets Leo’s brightest star, 1st-magnitude Regulus, as darkness falls this evening. The planet appears 1.2° north (to the upper right) of the star and shines more than 100 times brighter, so binoculars will provide the best view. (Jupiter and Mars will make an even closer pass before dawn tomorrow.) The Moon reaches perigee, the closest point in its orbit around Earth, at 4:23 p.m. EDT. It then lies 222,700 miles (358,401 kilometers) away from us. Related Articles A pair of close encounters Southern Delta Aquarid meteor shower peaks at the end of July From Astronomy - The Sky this Week