June is named for the Roman goddess Juno, wife of the king of the gods, Jupiter. Juno is also the name of a large asteroid, the third discovered. Unfortunately, the asteroid Juno sets in the west this June around sunset.
Brilliant Venus low in the west-northwest will still be the first object visible in the evening sky but there is a contest between two bright stars to see which of them will be visible first.
Just south of the zenith, the point directly overhead in the sky, is the bright red star Arcturus. There is an easy way to identify Arcturus later in the evening. Find the big dipper high in the north. Follow the handle of the dipper from the bowl to the end and follow this curved line southward. It will lead directly to Arcturus.
This process is called “arcing to Arcturus”. In competition with Arcturus for the first star visible at twilight is the bright white star Vega, all alone high in the northeastern sky. Because of precession, a slow change in the direction towards which the earth’s rotation axis points, Vega will be the “North Star” in 14,000 CE. You should be able to spot Arcturus and Vega between 9 and 9:30 p.m.
June rhymes with loon, but the only loons in the starry night sky are those that just happen to be flying through. But rising in the east just below Vega is the closest thing to a loon in the starry sky, Cygnus the Swan.
The bright stars of Cygnus form a nearly perfect Roman cross in the sky. The cross piece of the Roman cross marks the wings of the swan and the straight piece marks the long neck and body of the swan. Cygnus is visible when the sky is thoroughly dark.
June 21, 6:28 a.m. CDT, brings the summer solstice, which marks the beginning of summer in the northern hemisphere. During the year the altitude of the sun in the sky at noon varies from lowest in the winter to highest in the summer. At the summer solstice in Mankato, the altitude of the sun reaches its maximum of about 69 degrees.
June also rhymes with moon, and this June 26 brings us a partial lunar eclipse. A lunar eclipse occurs when the full moon moves into the shadow of the Earth cast by the sun.
For a partial eclipse the moon moves only partly into the umbra, the darkest part of the shadow. Unfortunately this eclipse only begins when the moon is setting in the west. The setting full moon will start being eclipsed at about 4 a.m. CDT. Look for the setting moon to be redder than usual.
The first astronomical event to be recorded in America was a lunar eclipse observed June 25, 1638, by an unknown observer from what today is Rhode Island.
June 30 is an ominous date is astronomical history. On that date in 1908 (June 29, 6:14 p.m. CST), a large body from space collided with the Earth over the Tunguska river valley in Siberia.
This impact had the energy of a hydrogen bomb. When the investigators got to the site decades after the event they found millions of trees knocked down by the force of the blast, but at the center of the impact there was no crater and there were no meteorites.
Arguments continue about what hit the Earth, but I like the suggestion that a small icy comet exploded in the atmosphere over Siberia and then the icy pieces, like the icicle dagger in a murder mystery, melted away, leaving no evidence behind.
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