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Astronomy Picture of the Day


Photo of the Week.. Capella and Kids rising with the 4-meter telescope on Kitt Peak in the foreground reminds us of the coming winter.

Astronomy news for the week starting Friday, June 14, 2002.

Phone: (217) 333-8789
Prepared by Jim Kaler.

If you like stars, go to STARS: Portraits of Stars and their Constellations, compiled from previous stars of the week. Access Skylights' Archive, now available from January 4, 2002, to the present. Enjoy photographs of the January 20, 2000 total eclipse of the Moon. Watch planets move against the background stars. See sunsets, rainbows, the Moon and planets, and other sky phenomena in Sunlight.

The Moon passes through its first quarter this week, reaching the phase on Monday, June 17th, about the time of sunset in the Americas, allowing you to see a near-perfect "half-moon." The "half-moon" term comes from seeing half the lunar disk illuminated by the Sun, the "quarter" from the quartering of the orbit, since the Moon will be 90 degrees to the east of the Sun. Just a day later the Moon passes through its perigee , where it is both closest to the Earth and of greatest angular diameter (the increased apparent size not visible to the eye without some kind of comparison). On Friday, the 21st, the Sun will pass the Summer Solstice in Gemini at its most northerly point on the ecliptic. The first quarter will therefore be just shy of the Autumnal Equinox in Virgo, the Quarter closely marking the spot near where the Sun will be on the first day of autumn.

About all that is left of the great planetary gathering of 2002 is Jupiter, now low in the west in evening twilight, and much higher brilliant Venus, which will soon be all that remains. In memory, it will stay with us throughout the Summer, not disappearing into twilight until mid-autumn. Venus's brother planet, little Mercury, has now switched sides, and is a growing morning object, visible very low in twilight eastern skies. These two, called "inferior planets" because they are inside the Earth's orbit (or "below" the Earth), can never attain great angles with respect to the Sun, Venus's maximum about 47 degrees (which it will attain on August 21st), Mercury's only about 28 degrees. Neither can therefore be seen at midnight. Though Venus can be beautiful in a dark sky, it at best always either sets shortly after the end of evening twilight or rises shortly before the start of morning twilight. Mercury can be seen only in twilight. (Venus, however, is bright enough to be seen in full daylight; both can easily be found in daylight with a telescope.)

With the quarter Moon near the autumnal equinox, find Leo to the west of the Quarter, Virgo to the east of it. While Leo is a fine figure that actually sort of resembles the Lion it is supposed to be, Virgo is little more than a sprawl of stars. Both constellations, however, have bright luminaries, first magnitude Regulus in Leo, Spica in Virgo, Spica the hotter and bluer of the two. Down and to the right of Spica find the prominent distorted box the makes Corvus the Crow, while just below the bright star is the remains of the tail of Hydra, the Water Serpent. Farther down lie the stars of Centaurus, the Centaur. Virgo is perhaps best known for its "containment" of the great Virgo cluster of galaxies, which lies vastly farther than Virgo's stars, Spica 260 light years distant, the galaxy cluster 45 MILLION light years away.

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