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What's in the Sky?

Stargazing for September


For The Enterprise

September brings us the start of autumn, with noticeably shorter days and longer nights. At the start of the month, sunset comes at 7:42 p.m. By the end of the month, sunset has moved up to 6:46 p.m., almost an hour earlier.

Jupiter is almost gone from the evening sky, moving closer and closer to the Sun. At the start of the month Jupiter is about 15 degrees above the horizon at sunset, and has set itself by 10 p.m. By the end of the month, it sets at about 8:15 p.m.

The first quarter Moon greets September on the 1st. Full Moon occurs on Sept. 7, with new Moon following two weeks later on the 21st.

September evenings bring the rise of autumn constellations in the eastern sky. One particularly noticeable figure is the "great square" in the constellation Pegasus. While the winged horse of mythology (Pegasus) is difficult to see, the great square is easy to find. All four corners of the square are occupied by stars of similar brightness, all between magnitude 2.1 and 2.8. The square is "tilted" in orientation as it rises -- see if you can locate it.

Once you find the constellation, look for the star that is the upper-left corner of the square. Extending to the north from this star, you should be able to make out two "lines" of stars that are roughly parallel to the constellation Andromeda. Above and to the north of these lines, find a W-shaped constellation, Cassiopeia. The "W" is fairly distinct.

Now, on a nice, dark night, go back to those parallel lines, and refer to the sky picture accompanying this article. Just above the middle of the two lines, see if you can make out a fuzzy "star" that is barely visible. A pair of binoculars will help. That fuzzy spot is not a star. It is an entire star system, the Andromeda galaxy, our nearest large galactic neighbor. If you can find it, you are gazing at light that left the stars of Andromeda about 2.2 million years ago! Andromeda is the only object outside our own galaxy that is visible to the naked eye.

Finally, a note from August. Easily the most common question I answered in August was, "I read that, on August 27, Mars will be closer than it has ever been, and will be as large as the Moon. Is it true?" This story is not true -- it has been making an annual trip around internet sites and e-mails since 2003. There was some truth to the story in 2003. In that year, Mars made its closest approach to Earth in thousands of years, coming the closest on Aug. 27. Internet postings that didn'’t mention the year that the event occurred continue to be circulated -- with resulting excitement and confusion. Furthermore, some reports in 2003 noted that, through a telescope, Mars could appear as large as the Moon does to the naked eye. That mention got twisted to "Mars will be as large as the Moon." In 2003, Mars was bright, only outshone by the Moon and Venus, but still was much smaller than the Moon, appearing only as a bright "star." This August, Mars is about as far away as it can get from us, on the far side of the Sun.

Remember this article next August when your friends ask. The question will probably come around again!

Jim White is an amateur astronomer who lives in Trout Lake.


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