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The Honolulu Advertiser
Posted on: Sunday, November 30, 2008

Brilliant Venus and Jupiter pair up in the night sky

By Mike Shanahan
Bishop Museum

Venus and Jupiter, the two brightest planets, pair up in the early-evening sky early in December. Throughout November we had watched these two planets draw closer and closer in the western twilight sky. In late November and early December, these two planets will appear right next to each other. While the two planets are really very far apart from each other in space, they appear like neighbors in our earthly evening sky.

The closest approach of Venus and Jupiter during this entire November-December conjunction happens today; Venus and Jupiter appear almost exactly 2 degrees apart. Two degrees is about the width of a finger held at arm's length, or about four times the width of the full moon. Venus shines at minus 4.2 magnitude, brighter than anything in the sky except the sun and the moon. Jupiter, shining at minus 2 magnitude, is the next-brightest object in the sky, though it's more than six times dimmer than Venus. Venus will be to the left and a little below Jupiter this evening. Look for the planets in the west from about 6:40 p.m., when they are about 25 degrees above the western horizon (somewhat more than the width of two fists held at arm's length). The planets set at 8:40 p.m. Adding to the striking view, the early crescent moon will be just below Venus and Jupiter tonight. This gives you a chance to see the three brightest objects of the night sky — the moon, Venus and Jupiter — clustered together in a small part of the western sky.

Tomorrow, Venus and Jupiter will be nearly as close (2.1 degrees) as they were the night before. The moon will still be nearby, though tomorrow it will be just above the two planets, rather than just below them.

As December progresses, these two shining planets draw apart. On each evening in December, Venus will appear to be about 1 degree farther away from Jupiter than it was the night before.

MERCURY JOINS IN

Then another planet joins the gathering. The planet Mercury will appear below Jupiter and should be visible by Dec. 25, about halfway between Jupiter and the horizon at about 6:25 p.m. Night by night for the last week of December, Mercury will draw closer and closer to Jupiter. By Dec. 31, Jupiter and Mercury will appear side by side in conjunction, much as Venus and Jupiter did at the start of the year. Mercury shines at minus 0.68 magnitude and will be to the left of Jupiter on Dec. 31. However, you will have a very narrow window to catch this sight. On Dec. 31, for example, it will not be dark enough to see Jupiter and Mercury until about 6:30 p.m., and the two planets will set just after 7 p.m. In contrast, Venus, which sets around 8:40 p.m. at the start of the month, will not set till 9:10 p.m. by the end of December.

MARS MISSING IN ACTION

Mars is not visible at all this month; on Dec. 5 it is in conjunction with the sun, which means that the red planet is exactly on the other side of the sun from us. We won't see Mars until it pops into the morning sky in March.

SATURN BRIGHTENS SKY

The only planet in the morning sky is Saturn. At the start of December, Saturn rises almost exactly due east at 2 a.m.; it will be halfway up in the sky by daybreak. It shines at first magnitude. By the end of December, Saturn rises around 12:15 a.m. and is high up in the south by daybreak.

GEMINID METEOR SHOWER

The Geminid shower peaks on the evening of Dec. 13 and 14. The Geminids are generally at least as good as the summer Perseids, but don't get as much attention, perhaps because they happen in a season where the weather is cloudy in much of the northern hemisphere. That said, this will not be a great Geminid year. The full moon will interfere with the shower this year, and only the brightest of the Geminid meteors will be visible. If you want to try your luck, stay up late on Dec. 13, and look for meteors from about 10 p.m. all the way to dawn on Dec. 14.

URSID METEOR SHOWER

The Ursid shower is not one of the big meteor showers, but its peak on the night of Dec. 21 to 22 coincides this year with a waning crescent moon that should not provide too much interference. You might see up to five meteors per hour in the wee hours — stay up late on Dec. 21, and look for the meteors early in the morning of Dec. 22). The shower is called the "Ursid" because the meteors seem to come from the direction of the constellation Ursa Major (Big Bear, otherwise known as the Big Dipper). This constellation rises by 1 a.m. on the night of Dec. 21 and 22.

WINTER SOLSTICE

Winter begins on Dec. 21 at 2:05 a.m. Hawai'i Standard Time this year. This is the shortest day of the year in the northern hemisphere. In a location like Seattle, Wash., (47 degrees north latitude) the sun rises at 7:55 a.m. and sets by 4:20 p.m. on the first day of winter, giving Seattleites less than 8.5 hours of daytime. In Honolulu, on the other hand, the sun rises on the first day of winter at 7:05 a.m. and sets at 5:55 p.m., so we still get nearly 11 hours of daytime even on the shortest day of the year.

AN OLD FRIEND RETURNS

The Southern Cross, or Crux, returns to Hawai'i's skies each December. (The Southern Cross is not on our December star map; the sky map is for our current evening sky, and Crux is in the pre-dawn morning sky.) Around Dec. 10, look for the cross rising around 5:45 a.m. You need an absolutely flat horizon (the sea is ideal) and you need a cloudless view of the south. If you are looking due south, Crux will be a little to the east of due south. You'll have to look fast, since the sky start to lighten up by 6 a.m. By Christmas Day the Southern Cross rises at 4:45 p.m., so you'll have more than an hour to spot it before day begins. By New Year's Eve, Crux is up by 3:45 a.m.

THE DECEMBER SKY MAP

The most distinctive constellation in this sky is Orion the Hunter. Orion is the easiest constellation to find; its hourglass shape, famous belt and two bright stars (Betelgeuse and Rigel) make the constellation an easy target. Follow the belt of Orion higher in the sky and it will direct you to Taurus the Bull and then to the Pleiades. Follow Orion's belt lower in the sky, and you'll find Sirius, the Dog Star. Sirius shines at minus 1.47, much brighter than any other night star; its name in Hawaiian, "A'a," is the same as the Hawaiian word for "fire." As Sirius rises, the thick atmosphere near the horizon bends the star's light and makes it seem to twinkle in different colors — from blue to red.

Also in the eastern sky on this map are the Gemini Twins and Auriga the Charioteer, two other great constellations of the winter skies.

The Great Square of Autumn is high overhead, and starting to sink to the west. This is one of the names for the square of four stars at the heart of Pegasus, the Flying Horse.

In the southern portion of the map, look for two bright and lonely stars. First magnitude Fomalhaut is high in the south. It's in the constellation of Piscis Austrinus, the Southern Fish, although that constellation is too faint to show on our map. Achernar is low in the South. It's quite bright, 0.43 magnitude. The rest of its constellation, Eridanus the River, is not shown on the map, since the other stars of that constellation are not very bright.

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