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 .


Photo of the Week.. A remarkable "heiligenschein" ("holy glow") surrounds the invisible shadow of an airplane 35,000 feet above the prairie floor. You can see the same thing surrounding the shadow of your head seen against dewy grass, the effect caused by the "backscattering" of sunlight. Stretching very faintly to the left is the shadow of the aircraft contrail.

Astronomy news for the week starting Friday, February 14, 2003.

Happy Valentine's Day to all.

Our Moon brightens during week, cutting out the view of the faintest stars, as it passes from waxing gibbous through full on Sunday, February 16, just about the time of Moonrise in North America, and then into waning gibbous. While the full Moon is only double the reflecting area of the quarter, it is some eight times as bright, since the shadows of craters and mountains disappear, and 180 degree reverse reflection of sunlight is so much more efficient. With the Sun now climbing ever higher up the ecliptic, the full Moon is seen more to the south each month, and this time it finds itself nestled near the Sickle of Leo. The night before full, on Saturday the 15th, the near-full-Moon will be seen just to the east of bright Jupiter.

The giant planets now rule the non-lunar nighttime sky, Saturn retrograding westerly in eastern Taurus, Jupiter in eastern Cancer, two constellations of the Zodiac to the east. Saturn's angular speed against the starry background has slowed in preparation for it going back to direct motion, so Jupiter is catching up with it a bit, though not by very much. Saturn transits the meridian high to the south early now, around 7:30 PM, by which time Jupiter shines high in the east. In the morning sky, Venus is getting notably closer to the Sun, now rising about an hour before the onset of dawn. It then brilliantly punctuates the growing twilight to the southeast. Look then for Mars rather well to the west of Venus.

Three other planets make invisible passages of a sort. Uranus, near the Capricornus-Aquarius border, is in conjunction with the northerly-moving Sun on Monday the 17th, while on Thursday the 20th, Mercury is in conjunction with Neptune, both in western Capricornus and to the west of the Sun.

While Orion stalks the sky high to the south, the greater glory goes to the heavens' brightest star Sirius, down and to the left of the giant hunter. The luminary of Canis Major, the Larger Dog, Sirius twinkles madly in the cold winter air of the northern hemisphere, the effect caused by starlight jiggling through patches of warmer and colder atmosphere on its way to the eye. The star can now be compared nicely with Jupiter, which shines with a much steadier light. While the distant stars appear essentially as points to us, planets present extended telescopic disks. Because the twinkling from one part of the disk averages out the twinkling from another part, the effect becomes nearly unnoticeable. To the northeast of Canis Major barks Canis Minor, the Smaller Dog, with Procyon as its first magnitude leader. By 9 PM, Canis Major walks the sky to the south, allowing a fine glimpse of the bright stars of the great ship Argo, which sails to the southeast of the larger celestial dog.
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