Skylights featured on Astronomy Picture of the Day

Scout Report Selection Webivore Selection SpaceCareers Selection

Skylights featured nine times on Earth Science Picture of the Day: 1 2 3 4 5 6 7 8 9 -- Full List Restored!


Photo of the Week. A complex lightning display rips the sky from a thunderhead 60 miles away. The curve of stars up and to the right is Corona Australis, the Southern Crown. See full resolution.

Astronomy news for the two weeks starting Friday, September 9, 2016.

The next skylights will appear September 23.

The Moon begins our session in its first quarter on Friday the 9th, to the northeast of Saturn and above Mars ,leaving the planets behind as it grows in the waxing gibbous phase that terminates at full Moon on Friday the 16th, when it will undergo another minimal penumbral eclipse that in any case is nowhere visible from the Americas. Of more significance, this full Moon is the famed Harvest Moon. At this time of year, the evening ecliptic in the east bears its most shallow angle to the horizon with the result that the intervals between successive Moonrises from one night to the next are minimized, giving us lots of early evening moonlight for outdoor activities, such as harvesting. Two days after full, the Moon passes perigee, where it is closest to Earth, making it even brighter, though not really noticeably so. The Moon then gibbously wanes, terminating our fortnight at third quarter on the morning of Friday the 23rd with the moon high in the sky. Look the night of Tuesday the 20th to see the Moon to the west of Aldebaran. After occulting the star during the day, the Moon will be just east of the star the following night.

The big event is the passage of the Sun across the autumnal equinox in Virgo at 9:21 AM Central Daylight Time (10:21 EDT, 8:21 MDT, 7:21 PDT) on Thursday the 22nd, which begins autumn in the northern hemisphere, spring in the southern. Discounting the effects of atmospheric refraction and the finite angular diameter of the Sun, at that time the Sun rises due east, sets due west, days and nights are of equal length, and the Sun rises at the north pole and sets at the south pole. Moving south against the constellations of the Zodiac, it will bottom out 24.4 degrees south of the celestial equator on December 21, the first day of winter in the northern hemisphere.

Mars and Saturn are quickly separating as Mars moves to the east. Both still in the southwest in early evening, they set just after 11 PM at the beginning of our fortnight, while by the time of the equinox Saturn (still north of Antares in Scorpius) sets about 10 PM, while Mars lingers for about an hour. With a good horizon, Venus is visible in western twilight, while Mercury disappears, as it goes through inferior conjunction with the Sun (on this side of the Sun) on Monday the 12th.

Ever so slowly, the stars of summer are being replaced by those of autumn. As the Big Dipper glides off into the northwest, the "W" of Cassiopeia climbs the northeastern sky. In mid-evening look about halfway up the sky to find bright Altair, the luminary of Aquila the Eagle, which is nicely set within the Milky Way. While rarely so represented, Altair with its two flanking stars (Tarazed to the north, Alshain) look much like a bird in flight, and have been taken for an airplane with wing lights. Up and to the left of Altair, find the compact and delightful Delphinus, the Dolphin, which looks rather lie a hand with its finger pointing south.
Valid HTML 4.0!