Skylights featured on Astronomy Picture of the Day

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Skylights featured five times on Earth Science Picture of the Day:
1 , 2 , 3 , 4 , 5

Clear Air Subsun

Photo of the Week.. A brilliant "subsun," caused by reflection of sunlight from invisible ice crystals below a high- flying airplane, appears to float in clear air above a river gorge in California, the river's waters also reflecting sunlight. This picture was featured on the Earth Science Picture of the Day

Astronomy news for the week starting Friday, May 20, 2005.

The Moon rolls through its glorious full phase on Monday the 23rd, shortly before moonrise in North America, meaning that the full Moon will rise just after sunset. Lovely as it is, the full Moon, or near-full-Moon, is the bane of both amateur and professional astronomers. It is so bright that it washes out fainter starlight. Professional observatories in fact are divided into "dark runs" between third and first quarters and "Moon runs" between first and third (where full Moon is second base...), during which time one can observe only brighter objects, and then usually spectroscopically. Even if one is into lunar studies, at full Moon, crater shadows are hidden such that little geological (selenological?) relief is seen. The beauty of the lunar disk is nevertheless there. The early part of the week then sees the last of the waxing gibbous phase, while the later part sees the beginning of the waning gibbous.

The Moon makes two passages of note. On the night of Friday May 20, the waxing gibbous will appear just to the east of first magnitude Spica in Virgo, the Moon, the star, and the planet Jupiter (well to the west of Spica) making a fine sight. Then the morning of Tuesday the 24th, only half a day past full Moon, the Moon will not only pass, but will occult (cover over), first magnitude Antares in Scorpius for most of North America. Times vary, depending on location. "Ingress," or disappearance, ranges from about 4:20 AM EDT in the east (in twilight) through 3 AM CDT in the midwest, 1:20 AM MDT in mountain country, to 11:50 or so PM PDT on the west coast. "Egress," re-appearance, in the east is rendered mostly invisible because of the bright sky. For the three other regions it will take place about 4 AM CDT, 2:30 AM MDT, and 1:05 AM PDT. Because of the very bright Moon, the event will require a telescope or larger binoculars. Knowing the rate of motion of the Moon, astronomers can measure the angular diameters (and with distances the physical diameters) of stars by how long they take to disappear behind (or reappear from behind) the lunar edge.

Saturn and Jupiter still dominate the evening sky, Saturn (in Gemini) to the northeast and setting at midnight, Jupiter (in Virgo) to the south, setting at 3:30 AM just an hour after Mars (in Aquarius, below the "Circlet" of Pisces) rises. Though Venus is beginning to make its appearance in the west northwest, it is still very low and hard to find.

Virgo, crossing the meridian between about 9 and 10 PM, is among the largest constellations of the Zodiac (if not of the whole sky) and contains one of the hottest of first magnitude stars, the close double star Spica, The star lies at the center of a loose ring of other constellations, Corvus (the Crow) to the west, the tail of Hydra (the Water Serpent) due south, Libra (the Scales) to the east, and Bootes (the Herdsman) with Arcturus rather well to the north.
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