June always marks the beginning of summer for us in the northern hemisphere. This year that will happen on Saturday the 21st at exactly 6:51 a.m.
That is the highest point that the sun will reach for the year. That will be about 68 degrees high in our sky at high noon, when the sun is at the meridian. By contrast it is only 24 degrees high in our sky on the first day of winter, which is Dec 21.
The highlights this month include several very nice close conjunctions, another Comet Panstarrs, the Bootid meteor shower, the two largest asteroids, Ceres and Vesta, close together in the constellation of Virgo, and even a triple transit of three of Jupiter’s largest moons.
So try to get out under the warmer skies this month to enjoy and appreciate the many celestial events always going on above us and try to enlarge your perspective of where we really are, and try to solve or at least wonder about the hidden mysteries each of these events represents. This way you will begin to attain a much larger cosmic perspective and see what is really possible once we learn more about where we really are and where we are going.
Jupiter is slowly slipping away into the western horizon after gracing our evening skies since fall of last year. Watch as a slender waxing crescent moon joins the king of the planets on June 1, low in the western sky about 45 minutes after sunset in the constellation of Gemini the Twins just below Castor and Pollux. Notice that our first planet, Mercury, will be about 15 degrees below and to the right of Jupiter.
Try to watch the triple shadow transit of Callisto, Ganymede, and Europa during the day on June 3. You will need a telescope and need to know exactly where to look, but Jupiter is up in the daytime and the shadow transits will be visible. They start at 11:22 a.m. and end at 3:43 p.m. Many observers have never even seen a double transit so this will be a treat. Think about what is really going on as you watch this rare event. Galileo first observed this through his telescope and saw how it demonstrated a whole miniature solar system at work.
The Danish astronomer Ole Romer used eclipses of Jupiter’s moons to calculate the speed of light. It took less time when the earth was moving toward Jupiter and more time when it was moving away from Jupiter. This was done back in 1668 to 1674. His speed came out too slow but he did prove that the speed of light was finite. Try to see if you can calculate this for yourself. That will give you a much better sense of the real distances and speeds involved within our own solar system.
Mars is past its peak for the next two years, but it is still much brighter than usual in Virgo. Watch as a bright waxing gibbous moon joins the red planet on the evening of June 7.
Our two biggest and brightest asteroids, Ceres and Vesta, will be very close together in Virgo by the end of this month. They will be just 23 arc minutes apart, which is less than half a degree of the sky, which is the width of the full moon and the sun.
You will need a small telescope to spot them. Vesta reflects nearly five times as much light from its surface as Ceres, which is the largest asteroid at about 600 miles in diameter. This, along with many other fascinating mysteries about these dwarf planets, will be solved when the Dawn spacecraft enters orbit around Ceres next summer.
Saturn is also just past its peak but still offers a wonderful sight through telescopes. It now rises just before sunset in the eastern sky. The ringed planet can easily be found in Libra, the very next constellation to the east of where Mars is currently located in Virgo.
Venus remains as the only bright morning planet. It rises about two hours before sunrise in the constellation of Aries the Ram and then enters Taurus the Bull during the middle of the month. A waning crescent moon will join the brilliant planet on the morning of June 24, just after summer starts. Look low in the eastern sky 45 minutes before sunrise. The placement of this close conjunction will be very dramatic, right between the V-shaped Hyades star cluster marking the face of Taurus and the famous Pleiades, or seven sisters, cluster of about 400 stars that are about 400 light years away, which is when Galileo first improved the telescope and used it for astronomy.
Comet Panstarrs should reach about 8th magnitude. With a telescope or good binoculars, you should be able to see it in Ursa Major, which is commonly known as the Big Dipper, starting this month. There will be a nice 10th magnitude galaxy in the same field of view. Then this comet will drift into Leo Minor and then float directly above the sickle shape of Leo’s head. The interesting thing about this comet is that if it would have arrived six months earlier or later, it would have grazed the earth and become very brilliant at magnitude minus 5, which is what comet ISON was predicted to do before it broke up after going around the sun.
June 3. The Hale 200-inch telescope was dedicated on this day in 1948.
June 4. The Compton Gamma Ray Observatory was allowed to re-enter our atmosphere on this day in 2000. It was only orbiting for nine years, but it discovered numerous amazing things about our high-energy universe, including about one gamma ray burst per day.
June 5. First-quarter moon is at 4:39 p.m.
June 7. The moon passes less than 2 degrees south of Mars tonight.
June 10. The moon passes less than 1 degree south of Saturn tonight.
June 13. Full moon is at 12:11 a.m. This is also called the Flower or Strawberry Moon. James Clerk Maxwell was born on this day in 1831. He is known as the father of modern physics for his work in developing the equations to explain and use the electromagnetic fields that Michael Faraday first discovered. Einstein’s general theory of relativity was made possible by the genius of these two great scientists. Pioneer 10 left the solar system on this day in 1983.
June 16. On this day in 1963, Valentina Tereshkova became the first woman in space and is still the only solo space flight by a woman.
June 18. Sally Ride became the first American woman in space on this day in 1983.
June 19. Last-quarter moon is at 2:39 p.m.
June 21. The summer solstice is at 6:51 a.m.
June 22. On this day in 2000, NASA announced evidence of liquid water on Mars.
June 24. The moon passes just over 1 degree south of Venus this morning.
June 26. Charles Messier was born on this day in 1730. He developed a catalog of 110 celestial objects, many of which can be seen with the naked eye or just a pair of binoculars.
June 27. New moon is at 4:08 a.m. The Bootid meteor shower peaks this morning. This is not usually a great shower but it could always surprise us. The meteors enter the atmosphere at only 11 miles per second, which is the slowest of any shower.
June 29. George Ellery Hale was born on this day in 1868. He designed and engineered the four consecutive largest telescopes in the world from 1899 through 1940.
June 30. On this day in 1908, the Tunguska impact destroyed about 1,000 square miles of Siberian forest and about 80 million trees. It exploded about 5 miles above the surface of Earth with the force of 20 megatons of TNT, or 1,000 times the power of the Hiroshima atomic bomb.