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Brilliance of Venus slowly sinks below horizon

By Mike Shanahan

POSTED:
LAST UPDATED: 09:07 p.m. HST, Aug 05, 2011


Venus has blazed like a torch in the west throughout the summer of 2010. However, it's time to say goodbye to the planet that we call both our sister planet and "the evening star."

For the first two weeks of October, look for Venus low in the west as it gets dark about 6:30 p.m. Venus is still incredibly bright, at minus 4.8 magnitude. That's more than 100 times brighter than any star in the October evening sky.

Through the first half of October Venus emerges in the dusk at about the same time (6:30 p.m.) but sets earlier night by night. By Oct. 10 it will set at 7 p.m., which means you have only about 30 minutes to see it at all. By Oct. 15 Venus sets at 6:30 p.m., right as it is emerging from the dusk. Given that, you can pretty much assume that Venus is "gone, baby, gone" by Oct. 15.

Jupiter dominates

As Venus vanishes, the planet Jupiter comes forward to dominate the October evening sky. Shining at minus 2.9 magnitude, Jupiter is by far the brightest light in the sky except for Venus. At the start of October, Jupiter is rising above the eastern horizon at dusk. For those first two weeks of October we'll have "dueling planets": Venus shining low in the west while Jupiter rises in the east. Look for this phenomenon around 6:45 p.m. from Friday through Oct. 10.

In early October Jupiter will climb the eastern sky in the evening, be high overhead about midnight and set in the west at dawn. By the end of the month Jupiter will be halfway up in the east at dusk, will be overhead at 9:30 p.m., and will set in the west around 3:30 p.m.

The planet Mars is just above Venus for the first half of October, until Venus does its vanishing act around Oct. 15. The red planet will remain low in the western sky at dusk for the entire month, setting around 7:45 p.m. at the start of October and 7 p.m. at the end.

However, Mars has really become a bit player by now, hundreds of times dimmer than Venus. Try finding Mars around 7 p.m. on Oct. 9, using the moon. The crescent moon will be right above Venus on that night, and Mars will be the little dot of light straight to the right of the moon, with a faint orange color.

For a longer version of this article, go to the Bishop Museum planetarium page www.bishopmuseum.org/planetarium/planetarium.html and click on the October "Sky Column" on the right.

For the first days of October you might still catch Mercury in the eastern sky at dawn. It's very bright (minus 1), but your window to view the planet is small. Mercury rises at 5:40 a.m. on Friday, and day breaks 30 minutes later. After about Oct. 5, it's gone.

Orionid Meteor Shower

The Orionid shower peaks on the night of Oct. 21-22. For a few days on each side of Oct. 21-22, you may see an increase in meteor activity. The Orionid Show occurs every October as we pass through debris left over by Halley's Comet. The comet itself will not return till 2061. This is a modest shower and should be particularly modest this year due to interference with the full moon.

October Sky Map

The map for October 2010 is good for 9 p.m. at the start of October, 8 p.m. in the middle of the month and 7 p.m. at the end of October. We'll start in the southern part of the map and then work our way north.

The brightest object on the map is Jupiter, marked on this map by a large round dot in the southeastern portion of the sky. While Jupiter is just below the portion of Pisces called "the circlet," don't expect to find any part of Pisces unless you are in a really dark sky. It's a faint constellation. You should have much better luck finding the star Fomalhaut, which is south of Jupiter. Fomalhaut is a first magnitude star in the constellation of Piscis Austrinis, the Southern Fish. You won't be able to pick out the other faint stars (4th and 5th magnitude) in the constellation from city skies. However, even with a lot of light pollution, Fomalhaut will jump out at you. It's the only first magnitude star in the southern half of the sky on October evenings.

Overhead we can still see the summer triangle. This triangle is made up of three bright stars from three different constellations. This includes Vega, the brightest star in the triangle, in Lyra the Harp; Altair, in Aquila the Eagle; and Deneb, the dimmest of the three bright stars, in Cygnus the Swan. We've shown both the individual constellations and the triangle on our map.

Looking north, the North Star is a little harder to find than normal. Usually the Big Dipper is a guide to the North Star, but the Big Dipper is not visible in Hawaii in October's evening sky.

Instead, use the constellation of Cassiopeia. Cassiopeia is made up of five stars that form a squished "W" shape. The three middle stars of Cassiopeia's "W" form an arrowhead that points roughly to the North Star.

Mike Shanahan is director of education, exhibits and the planetarium at Bishop Museum.

 






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