Skylights featured on Astronomy Picture of the Day

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

Prairie Moon

Photo of the Week.. Prairie Sunset Moon.

Astronomy news for the week starting Friday, August 1, 2003.

The Moon, having recently passed its new phase, waxes through crescent the early part of the week, and achieves first quarter the night of Monday August 4 just about the time of Moonset in North America. The evening of Sunday the 3rd, the fat crescent will be just to the north of the star Spica. The first quarter appears midway between the classical figures of Virgo (which contains Spica) and Libra. The night of Wednesday the 6th finds the waxing gibbous Moon passing north of Antares in Scorpius, this star and Spica two of five first magnitude stars of the Zodiac (the others Regulus in Leo, Aldebaran in Taurus, and Pollux in Gemini). A day after first quarter, the Moon passes perigee, where it is closest to the Earth.

The only other "event" has Neptune at opposition to the Sun on Monday the 4th, the planet confined within the central figure of Capricornus. While invisible to the naked eye, it is an important body within the planetary system, as it is the last of the large planets. More-distant Pluto, well off the ecliptic in Ophiuchus, is more of a "planetary core," a body that did not have enough raw material to grow to a larger body like Neptune. Moreover, Neptune controls Pluto, as it goes around the Sun three times for every two orbits of Pluto (respectively rounded to 164 and 248 years), a phenomenon called a "gravitational resonance." In some sense Neptune therefore represents the "end" of the planetary system, as Pluto is more in league with a vast number of other bodies in the distant "Kuiper Belt."

So far as naked eye planets are concerned, we are left with dim, barely visible Uranus and brilliant Mars , to which the week really belongs, the latter to the east of Uranus, both in southern Aquarius. As August begins, the red planet rises in the southeast at 10 PM, the rise time moving up by about half an hour a week. Unmistakable, Mars is at magnitude -2.3, far brighter than the sky's brightest star, Sirius (which falls at magnitude -1.5), and is moving retrograde as it prepares for its August 28th opposition with the Sun, when it will be closer to us than any time in recorded history (though not by all that much).

Take time out from Mars to admire the northern sky. In the evening, the bright Summer Triangle climbs the eastern sky, its brightest star Vega in Lyra. This exquisite constellation consists of lovely parallelogram of stars that lie to the southeast of the luminary and one more to the northeast. The significance of the stars belie their seeming faintness, one (Epsilon) one of the most famed multiple stars in the sky, Sheliak (Beta Lyrae) one of the most famed eclipsing binaries. Right between Sheliak and Sulafat (Gamma) lies the telescopic "Ring Nebula in Lyra," a fine example of a dying star (with a ring of ejected gas) that is creating a white dwarf like Sirius B.

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