WHAT'S UP: The outlook for autumn

Sep 30, 2011


By Tuesday, the moon will be wearing its first quarter suit. The first quarter moon is what most people call a half moon; a half moon with its right-hand side illuminated. In this phase, though, we can only see half of half of (or one-quarter) the moon for the first time in the lunar month.

The first quarter moon rises at solar noon (about 1:30 p.m. in West Michigan) and sets in the middle of the night.
The moon will be full this season, big and bright, rising at sunset and setting at sunrise on Oct. 12 (the Harvest Moon), Nov. 10 (the Beaver Moon) and Dec. 10 (the Cold Moon).

The most captivating solar system object this season is Jupiter. Jupiter reaches the position in the sky (relative to the sun) called opposition on Oct. 29. Jupiter at opposition is like the full moon, rising at sunset, passing highest overhead in the middle of the night and setting at sunrise.

Bright and bold, Jupiter will be swimming in the sky with the water signs, riding above the head of the constellation Cetus the whale, just west of Pisces the fish.
At opposition, Jupiter is about four times farther away from Earth than is the sun, at a distance of about 400 million miles.

Jupiter’s father, Saturn, is out of the picture this season. Saturn is now just about opposite Jupiter in their orbits around the sun. From our vantage point, this puts Saturn deep in the glare of the sun.

Saturn reaches the position in the sky (relative to the sun) called conjunction on Oct. 13. Saturn at conjunction is like the new moon, rising at sunrise, passing highest overhead at noon and setting at sunset.

We won’t get a decent view of Saturn until 2012.

Mercury and Venus, the two solar system planets that forever chase the sun around the sky, are not well-situated for our viewing pleasure this season either.

Although Mercury reaches the position in the sky (relative to the sun) called greatest eastern elongation on Nov. 14 — the position at which we normally can get a glimpse of him in the evening after sunset — the circumstances of this alignment are not favorable. Mercury lies far to the southeast of the sun this time of year, so he sets only a few minutes after sunset.

Venus is near Mercury this season, and also sets shortly after sunset. We won’t be able to get a nice look at her until winter 2012.

And then there’s Mars — the up and comer of the autumn. Mars is lagging Jupiter in their cruises to opposition.

Presently, Mars rises after midnight, making the red planet a target for early birds. But all season long, Mars will rise earlier and earlier, eventually reaching opposition in early March 2012.

— By Doug Furton, a member of the physics faculty at GVSU. Send questions and suggestions to dgf@inbox.com.


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