June 2007

by Deane Morrison

The short June nights leave the stars and planets little chance to show their stuff, but this year they make the most of it. To the east, Jupiter rises at sunset to dominate the night. To the west, a parade of planets and stars pays its respects to queenly Venus. Elsewhere, the brilliant star Arcturus hangs high in the south and the Summer Triangle of bright stars rises in the northeast.

At the moment June begins, a moon just four hours past full is already halfway through its journey across the night sky. June's proper full moon arrives nearly a month later, on the morning of the 30th. Look for it very early or the night before, because actual fullness occurs a few hours after moonset that morning. This moon is called the strawberry moon by every Algonquin tribe; in Europe it is known as the rose moon.

Earth zips between Jupiter and the sun on the 5th, an event called the opposition of Jupiter because it puts the giant planet opposite the sun in the sky. All month, Jupiter remains very bright and is up most of the night, traveling near Scorpius and its brightest star, Antares.

Over near the western horizon, the Beehive star cluster passes just south of Venus the nights of the 12th and 13th. Binoculars will show both in the same field--a breathtaking sight by any measure. On the 17th, Venus will be one of four bright objects strung in a line. From upper left to lower right, they are Regulus, Leo's brightest star; Saturn; Venus; and a crescent moon. The next night the group will be tighter, the moon having moved in between Saturn and Venus. On the 30th, Saturn will be little more than a full moon's width above Venus; this will be 2007's most striking pairing of planets.

Mars, still low in the east at dawn, reaches perihelion on the 4th and continues its slow brightening. It's not very spectacular, but just wait till December.

Arcturus, anchoring the kite-shaped constellation Bootes, the herdsman, is flanked by the Coma Berenices star cluster to the west and Corona Borealis (the Northern Crown) to the east. Arcturus is a huge star of a type known as a red giant. If it were the size of an orange, our sun would be about as big as a BB gun pellet. Our sun will swell up like Arcturus in about five billion years, when it uses up the hydrogen fuel in its core. Our normally benign parent star will then expand past the orbit of Earth, and it will shine--for any intelligent beings who may still be around to watch--10,000 times brighter.

But if you think Arcturus is big, try Antares on for size. The diameter of Antares, classified by astronomers as a red supergiant, is several hundred times that of our sun. If Antares were the orange, Arcturus would be the BB and our sun would be a mere speck. When it finally exhausts its nuclear fuel, the core of Antares will collapse and the star will explode in a supernova 10 billion times as bright as the sun. But, being at least 400 light-years from Earth, it will only look twice as bright as the full moon. This could happen at any time, so enjoy the red star, whose name means "rival of Mars," now.

In the northeast, the bright stars Vega, Deneb and Altair are becoming prominent. Known as the Summer Triangle, they will be with us from now until well into the fall.

Summer arrives with the solstice at 1:06 p.m. on the 21st. At that moment, the sun will be directly over the Tropic of Cancer and the sun won't set till 9:03 p.m. CDT in the Twin Cities area. Farther north, daylight will last even longer.