Sky chart prepared by George Ayers.
The month of June is named for Juno, the Roman queen of the gods, the wife of Jupiter and the patroness of marriage. According to myth, Juno also had the power to see through a veil of clouds that her husband drew around himself to hide his misdeeds. So it is fitting that a space craft named Juno has been orbiting Jupiter for nearly three years, performing much the same function as its mythical namesake, except that the modern Juno uses scientific instruments and the power of mathematics – not magical powers and ancient spells – to better reveal Jupiter’s true nature.
Jupiter will be at its best for the year on June 10, but it does not usually reach opposition in June. However, summer always starts in June for us in the northern hemisphere. This month, that will happen at 11:54 a.m. on Friday, June 21. That marks the minute that the sun lies farthest north and highest in our sky, which is 68 degrees. That also marks the longest day and shortest night for us and the beginning of winter in the southern hemisphere. If you could photograph the sun at high noon about every other day from a fixed location for a whole year, the sun would trace out a slightly tilted figure eight in the sky; the sun will reach that highest point this month.
Although the nights are at their shortest now, this will be a good month to spend more time looking at the night sky, both because it will be warm out and because the June sky offers many highlights. Jupiter will reach opposition on the 10th; Mars and Mercury will have an extremely close conjunction in the evening sky a week later, on the 17th; a faint comet passes through Cetus the Whale; a fairly bright asteroid named Pallas reaches opposition in Coma Berenices just below the Big Dipper; and there will even be a minor meteor shower called the Bootids very close to where Pallas is on the 27th.
Jupiter has been rising about four minutes earlier each night all winter and spring, and it will finally pass directly opposite the earth from the sun on Monday, June 10. That means that the king of the planets will rise at sunset, reach its highest point in the sky at midnight, and not set until the sun rises. That is the best time to see any superior planet, because it also has to be at its closest to us at that time, which means that it will also be at its biggest and brightest for the year. This happens every 13 months for Jupiter and Saturn and every 26 months for Mars.
Jupiter spends one year in each of the 12 zodiac constellations, since it orbits the sun once every 12 years. Jupiter is at the midpoint of its retrograde or westward loop in the sky now. Notice that it is moving a little closer to Antares, the brightest star in Scorpius and one of the largest stars in our whole galaxy, at 700 times the diameter of our sun. However, Jupiter will not reach Antares because it will start its normal prograde, or eastward motion, against the fixed background of the stars again on Aug. 10. Since July 4, 2016, the Juno mission has been orbiting this planet in highly elliptical 53-day orbits. It continues to discover amazing things about this huge planet, which is 10 times the diameter of Earth.
It photographed huge colorful swirls all over the planet, but especially at the poles. It saw large permanent storms spinning around each of the poles, and it recently discovered that Jupiter has more things in common with Earth than just lots of lightning bolts every second and permanent northern and southern lights. Jupiter also has continually varying magnetic fields, also known as secular variation. It is caused by intense winds about 2,000 miles below the cloud tops of Jupiter on this rapidly spinning planet. Jupiter rotates once every 10 hours, at 28,000 mph at its equator, or 28 times faster than Earth. It’s even faster than the escape velocity from Earth, which is 17,000 mph or 5 miles per second.
Mars is slowly starting to set a little earlier each night in our evening sky. It can be found in Gemini now, directly below Castor and Pollux. On the night of Monday, June 17, and the next night, Mars and Mercury will pass within a third of a degree of each other, the closest they have been for 13 years. Notice that Mercury will be two magnitudes, or six times, brighter than the red planet, which is unusual, since Mars is usually much brighter, especially when it is near opposition. That is because Mars is on the far side of the sun now and Mercury on the near side. Watch for a couple of weeks as Mercury catches up with Mars. A slender crescent moon will join the pair on June 4. Then Mercury will sink out of sight again as Mars continues to get fainter as it gets farther away from us in the sky.
Saturn rises about two hours after Jupiter and can be found in Sagittarius, where it will spend a little over two years, since it takes almost 30 years to orbit the sun once. The ringed planet will rise at 9 p.m. by the end of the month and will reach its own opposition in July. You can finish up a short night of viewing the marvels of the summer night sky and the Milky Way, with its center located just below Scorpius and Sagittarius, by watching Venus rise only about an hour before the sun, well into morning twilight. Notice the waning crescent moon nearby on June 1. Then Venus slowly sinks even lower in the morning sky. By the end of the month, we will lose it completely in the sun’s glare.
A comet named ASASSN, discovered in 2018, will pass through Cetus the whale all month long. It will only reach 12th magnitude, so you will need at least an 8-inch telescope to see it. We have been very lucky over the past half year or more with a long string of fairly bright comets visible to us from Earth.
The third largest asteroid, 2 Pallas, at 340 miles in diameter, will reach opposition in Coma Berenices just below the Big Dipper this month. You will need a small telescope or a good pair of binoculars to see it because it will only reach ninth magnitude. That will make it three magnitudes, or about 15 times brighter, than the comet that is visible this month.
This month’s meteor shower, the June Bootids, caused by Comet Pons-Winnecke, which orbits the sun every 6.4 years, will produce only a few meteors per hour, or just above the background rate of stray meteors of three to four per hour, depending on the darkness of the sky at your location. The word meteor comes from the Greek “meteoros,” which means “high in the air.” Most of these meteors will burn up 50 to 70 miles above us, high in the ionosphere.
JUNE HIGHLIGHTS
June 3: The new moon is at 6:02 a.m. On this day in 1948, George Ellery Hale’s 200-inch Mount Palomar telescope, the largest in the world, was dedicated and saw first light.
June 4: The moon passes 4 degrees south of Mercury this evening. In 2000, the Compton Gamma Ray telescope fell out of orbit in a controlled crash over the south Pacific after it spent nearly 10 years in space discovering amazing things about the high-energy gamma ray universe, including about one gamma ray burst every day.
June 5: The moon passes 2 degrees south of Mars tonight. In 1989, Voyager 2 made its closest approach to Neptune. The last transit of Venus happened in 2012.
June 10: The first quarter moon is at 1:59 a.m. Jupiter is at opposition at 11 a.m.
June 13: In 1983, Pioneer 10 left our solar system. In 2010, the Japanese Hayabusa mission returned the first sample of an asteroid to Earth.
June 16: The moon passes just north of Jupiter tonight. In 1963, Valentina Tereshkova became the first woman in space. She still holds the record for the only solo spaceflight by a woman.
June 17: The full moon is at 4:31 a.m. This is the Strawberry or Rose Moon.
June 18: Mercury passes within one-third of a degree of Mars this evening in Gemini. The moon passes half a degree south of Saturn.
June 21: The summer solstice is at 11:54 a.m.
June 25: The last quarter moon is at 5:46 a.m.
June 29: George Ellery Hale was born in 1868.
June 30: In 1908, a comet or asteroid exploded a few miles over Tunguska, Siberia, creating a daytime fireball brighter than the sun. It exploded with the force of 20 megatons of TNT, or about 1,000 times the force of the first atomic bomb. It downed 80 million trees over 1,000 square miles, but no crater was ever found. One hundred five years later in nearly the same part of Russia, on February 15, 2013, a space rock 65 feet across exploded a few miles over Chelyabinsk. It did not create much damage.
Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.
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