June always marks the beginning of summer for us in the Northern Hemisphere. This year the summer solstice will happen June 21. The sun will reach its highest point in the sky that day, creating the longest day and the shortest night of the year for us.

The warmer nights of late spring and early summer will offer us some interesting celestial highlights. The quartet of morning planets has lost one member, our first planet, Mercury, and the other three actors are drawing farther apart. Jupiter will be the highest morning planet, rising three hours before the sun by the middle of June. Then our next-door neighbor, Mars, is next, nicely located right between the Pleiades and Hyades star clusters in Taurus. Last will be brilliant Venus, situated very low on the east-northeastern horizon just half an hour before sunrise. Mercury will reappear in the evening sky right next to Castor and Pollux in Gemini by the end of June.

Saturn remains as the star of the nighttime stage. After listening to and participating in an excellent presentation of the latest discoveries by the Cassini mission around Saturn, I will never look at the ringed jewel of our solar system the same. This is a far more amazing planet than I had ever imagined, even though I had spent many hours over 30 years observing it carefully through many different telescopes and sharing it with others.

Its amazing ring system is far thinner than I thought it was. It is only between 20 and 40 feet thick. The sheparding moons that keep gaps open in the rings show that the rings act more like water than solid particles. The rings display lighter areas that correspond exactly to mathematical fractional resonances created by the moons that orbit outside of its ring system. There was even a major collision or near-collision event as recently as 1984 that created a serious disturbance in the rings from which they are still recovering. Saturn now looks much more like a finely tuned musical instrument within reach of our knowledge, rather than just a distant, cold, giant ball of gas nearly a billion miles away.

Saturn will end its westward or retrograde motion with respect to the stars on June 14. Then it will return to eight months of direct eastward motion again. Saturn will spend the entire month within half a degree or less of a third-magnitude double star in Virgo named Porrima. Through a telescope you will be able to split this double star as a bonus to observing and enjoying the artistic and mathematical wonders of Saturn.

Also, we are in an eclipse season again. There will be two eclipses in June. There will be a partial solar eclipse visible over the Arctic on Wednesday during the new moon, and a nice total lunar eclipse during full moon on the 15th, visible almost everywhere except North America. The next total solar eclipse is Nov. 12, 2012, visible over Australia and South America. The next total solar eclipse visible over this country will not be until Aug. 21, 2017. The shadow cone of the moon will cut a narrow path across our continent from Oregon to South Carolina that day. We will be able to see part of a total lunar eclipse toward moon set on Dec. 10.

June 30 marks the anniversary of a major dramatic event that happened just 103 years ago. At 7:17 a.m. on that fateful morning, a giant fireball raced northward across the skies over Tunguska, Siberia. Eyewitnesses from 300 miles away heard deafening bangs and saw a fiery cloud on the horizon. Anyone within 40 miles was knocked to the ground or even knocked unconscious. Fortunately, this happened over a remote area of Siberia, and only a few reindeer herders were killed by this still mysterious event.

It was probably caused by a fragment of a comet or an asteroid about 50 meters across that exploded about 4 miles above the surface of Earth with the force of 10 megatons of TNT. That is 1,000 times the force of the atomic bomb we dropped over Hiroshima, or about the equivalent of one hydrogen bomb. No crater was ever found, but it did kill 80 million trees covering nearly 1,000 square miles. They did find microscopic silicate and magnetite spheres in the soil, but no larger meteorite pieces. There is a very intriguing lake named Cheko near the epicenter which may be young enough to have formed at the time of the explosion. The event did set the night sky aglow over Europe and Asia for several nights. It also caused reduced atmospheric transparency for several months around the world.

The explanations for this strange event vary from a black hole passing through the Earth to antimatter explosions to the usual way out for anything that is not easily explainable, aliens caused it. As recently as 1972, a 1,000-ton stone skipped off our atmosphere over the Grand Teton Mountains in Jackson, Wyo. If it would have come in at a slightly steeper angle, it would have hit Canada with the force of several atomic bombs.

JUNE HIGHLIGHTS

June 1: New moon is at 5:03 p.m. A partial solar eclipse will happen over the Arctic.

June 4: The waxing crescent moon passes under Castor and Pollux in Gemini this evening one hour after sunset.

June 8: First quarter moon is at 10:11 p.m.

June 10: The waxing gibbous moon passes below Saturn and Spica in Virgo this evening one hour after sunset.

June 14: The nearly full moon can be seen just to the left of Antares in Scorpius, which, at 700 times the diameter of the sun, is one of the largest stars in our whole galaxy of over 200 billion stars.

June 15: Full moon is at 4:14 p.m. This is also known as the Rose or Strawberry Moon. There will be a total lunar eclipse visible over Africa and Australia, most of Asia, and parts of Europe and South America.

June 20: Mars and the Pleiades fit into the same 5 degree binocular field of view in the morning eastern sky half an hour before sunrise.

June 21: Summer starts at 1:16 p.m. this Tuesday afternoon, marking the longest day of the year in the Northern Hemisphere.

June 23: Last quarter moon is at 7:48 a.m.

June 26: Charles Messier was born on this day in 1730. He was a French astronomer and comet hunter that established a catalog of 110 objects like galaxies, nebulae, and star clusters that proved not to be comets. He also discovered about a dozen comets.

June 28-30: The slender waning crescent moon will descend between Mars and Venus for three consecutive mornings in the eastern morning sky half an hour before sunrise.