The Enterprise - White Salmon, Washington

What's in the sky

Stargazing for September

September 04, 2012

September heralds the coming of fall. This year the autumnal equinox, the beginning of autumn, comes on Sept. 22. At that time, the Sun will lie directly overhead at the equator and the length of day and night will be about equal.

The bright planets are leaving the evening skies this September. Saturn and Mars are still visible, low on the western horizon right after sunset. They are visible to the naked eye, but much fainter than they were earlier in the year.

The predawn sky is another matter -- brilliant Venus and bright Jupiter dominate the eastern sky in the early morning hours. Uranus and Neptune are both in the southern evening sky, but these outer planets are faint and difficult to find without a telescope. Uranus will be at its closest for 2012 on Sept. 29.

Evenings may lack bright planets, but there is plenty to see during clear September evenings. Darkness comes earlier, allowing time to view truly dark skies before it is very late.

On Sept. 1, skies are completely dark by about 9:30 p.m. and at 8:25 p.m. by the end of the month. Back in mid-June, that didn't happen until about 11:30 p.m.!

Under dark skies (New Moon is Sept. 16), the familiar stars of summer still shine overhead. Cygnus the swan (also known as the Northern Cross), and Aquila the Eagle soar overhead. Rising higher in the eastern sky is an easy-to-identify constellation, Pegasus, the winged horse.

Pegasus is located just east of the Milky Way, high in the eastern sky in September. If you can make out a winged horse, you have a better imagination than I do. But Pegasus is readily identified by an almost perfect square of 4 stars, all of about equal brightness. To find it, face southeast, and look straight up. You should be able to make out the Northern Cross, in the overhead Milky Way. Look for the square to the left of and below the cross. If you have trouble finding it, look in the northeast for the prominent "W" shaped constellation Cassiopeia. Pegasus will be just to the right and below the "W."

The small but distinctive constellation Delphinius, the Dolphin, is to the right of the square. See the picture with this article, which should help.

If you have binoculars, you can try finding an interesting little star cluster that looks like a coat hanger, Brocchis cluster. To find it, locate the head of Cygnus the Swan, or the bottom of the Northern Cross if you prefer that name. That star is named Albireo. It's the star on the southern end of the cross. From that star, look about 1/3 of the distance from Albireo to the bright star Altair, which is south of Albireo.

Scan the skies with binoculars, and see if you can detect the coat hanger. It consists of a straight line of 6 stars, with 4 others making up the "hook" part of the coat hanger. It will appear upside-down as you see it. Again, the accompanying map may help. If you are able to locate it, let me know.

The Moon will be just past full when September starts, and will be full again at the end of the month, Sept. 30. In the early morning hours of Sept. 8, the Moon will lie just below Jupiter. The Moon will lie very close to Mars on Sept. 19, visible just before sunset if you have a good view of the western horizon.

Be sure to enjoy September skies when you can. It is a great month for stargazing, with still warm temperatures, earlier nightfall, and usually a good spell of clear weather!