Warm June nights provide great opportunities for stargazing. This month the planets will be on parade and an asteroid gets bright enough to view with binoculars or even the naked eye.
June opens with the planet Mercury reaching greatest elongation. This means that Mercury reaches it farthest point from the Sun as seen from Earth, so we have our best opportunity to view it away from the Sun's glare. But Mercury will still appear low on the horizon, about twenty degrees above the sun just after it sets. You can measure 10 degrees by holding your fist at arm's length from you; the distance from top to bottom of your fist on the sky is about 10 degrees. Mercury will appear about two fist widths above the horizon at sunset and sink below the horizon less than two hours later. Mercury shines at magnitude 0.52.
June 1 also opens with four planets in the night sky. While Mercury is still up after sunset you can also catch Venus, Saturn, and Jupiter spread across the sky. Mercury and Venus are about 22 degrees apart. Venus is lying even with the two "head" stars of Gemini: Castor and Pollux. Venus shines at a brilliant -4.26. Twenty-three degrees higher than Venus is Saturn, lying in front of Leo the Lion. Saturn is shining at magnitude 0.34. Then all the way across the sky, recently risen in the southeast, is Jupiter shining at magnitude -2.6. See if you can catch the moon rising behind Jupiter before Mercury has set in the west.
The asteroid Vesta reached opposition on May 31. But because of the full Blue Moon, it was not the best time to look for it because of the bright lunar interference. June 3 is probably the best night to find Vesta. At magnitude 5.4, Vesta may be found without optical aid, but it is easier to first use binoculars and then try to spot it without them. Vesta is nine degrees higher in the sky than Jupiter. The two are rising in the southeast after sunset. Vesta can be found in the constellation Ophiuchus, just over one degree from the globular cluster M107. Try catching the 8th-magnitude M107 and Vesta in the same field of view in a telescope. See what other asteroids will be easy to observe in 2007.
Venus reaches greatest elongation on June 8, and then begins to loop back toward the horizon each night, although it brightens as it sinks. It meets up with the Beehive Cluster on June 12, making for a great view in binoculars.
On the morning of June 13, observers in the western United States will be able to see the thin waning crescent moon occult, or hide, some of the stars of the Pleiades. On June 14 is the New Moon, occurring at 11:13 p.m. EDT. The next evening try to catch a young moon just after sunset, very low, as it sets after the Sun and before Mercury.
On June 18, the Moon sits between the brighter Venus and Saturn, with the bright star Regulus just beyond Saturn. On the next night, June 19, some observers will be able to catch the Moon occult the star Regulus as it passes in front of it.
For observers with large telescopes, Pluto reaches opposition on June 18 in the constellation Sagittarius. Pluto is a faint magnitude 13.9.
The official beginning of summer occurs on June 21 at 2:06 p.m. EDT for the Northern Hemisphere. The summer solstice marks the first day of summer and happens each year when Earth's North Pole is tilted toward the Sun. "Solstice" means to "stand still." In the past, people would watch the Sun climb higher and higher in the sky until the summer solstice, when it would seem to stand still. Because it is higher in the sky in summer months, we have longer hours of daylight and more direct rays of sunshine falling on our portion of the Earth.
The biggest show occurs at the end of June, as Venus and Saturn pass less than one degree from each other. Toward the end of the month of June people will be noticing that two bright "stars" are getting very close in the western sky. Venus is the brightest of the two at a dazzling magnitude -4.43, and Saturn is shining at magnitude 0.43. Their closest approach occurs on June 30, when they will be just 0.7 degrees apart. This day will mark the smallest conjunction of two naked-eye planets all year. June 30 is also the date of the Full Moon in June, with full phase happening at 9:49 a.m. EDT.
