The bright evening planets outnumber the morning planets by a 4 to 1 ratio during June. Low in the west-northwest sky, immersed in the evening twilight is dim Mars, with a much brighter Mercury passing close by during the middle and latter part of the month. Jupiter comes to opposition on the 10th and is a prominent object all through the night. Fainter Saturn follows Jupiter across the sky, trailing behind it by about two hours. Next month it will be Saturn’s turn to come to opposition. Finally, there’s brilliant Venus into her final full month as a morning star, sitting close to the east-northeast horizon just before sunrise.
In our schedule, remember that when measuring the angular separation between two celestial objects, your clenched fist held at arm’s length measures roughly 10 degrees. Here, we present a schedule below which provides some of the best planet viewing times as well directing you as to where to look to see them.
Planet Viewing Guide
Mercury — puts on an interesting show this month. The speedy little planet loses some luster in the first half of June, fading from magnitude -1.1 on the 1st, to 0.0 on the 15th. But it also comes into view significantly higher above the west-northwest horizon by mid-month. For observers around 40 degrees north, the time between sundown and Mercury-set increases during this time span from about 1 hour 10 minutes to 1 hour 45 minutes. By mid-month this planet seems unusually prominent because it outshines nearby Mars (see “Mars” below). Two bright stars are also nearby, Pollux and Castor, which represent the starry eyes of the Gemini twins. On June 4th, about 6 degrees to the left of Mercury will be the slender sliver of a waxing crescent moon, less than 40 hours past new phase. By June 23rd, having left Mars behind, Mercury reaches its greatest elongation from the Sun (25 degrees) this evening. The planet is only 39 percent illuminated at this particular greatest elongation and shines not too conspicuously at magnitude +0.5. On June 25th, if you extend an imaginary line from Castor to Pollux, then twice the distance between these two stars will bring you to Mercury. During this final week of June, Mercury gradually fades, becoming only about half as bright by month’s end, and is ultimately lost to view.
Venus — is visible this month solely because of its great brilliance (magnitude -3.9). It currently rises an hour before the sun, but that’s reduced to just 50 minutes by month’s end. If you look very low, near the east-northeast horizon about 30 minutes before sunrise you should be able to pick it up; scanning with binoculars will make the job easier. On the morning of June 1st, if you make a sighting, look about 7 degrees to Venus’s right for a very thin (5 percent illuminated) waning crescent moon, just two days from new phase.
Mars — has been on stage in our sky for more than 1½ years, but its reign of visibility will soon be coming to a close. On June 5th, a crescent moon will be positioned about 6 degrees to the upper left of Mars. Currently, the red planet sets in the west-northwest around 9:30 p.m. Mercury and Mars are within 1 degree of each other from June 16th to June 19th. On June 18th they’ll pass strikingly close to each other – within 0.3 degrees – with Mars situated directly below Mercury. Look low toward the west-northwest horizon about an hour after sundown. Binoculars will help greatly in spotting Mars, which now shines at magnitude +1.8 and is located far across the inner solar system, some 20.9 light-minutes away. Mercury gleams more than 4 times brighter at magnitude +0.2. The innermost planet is only about 7.6 light minutes away. Also take note of the twin stars of Gemini, Pollux and Castor, lurking to the upper right of the two planets.
Jupiter — in southern Ophiuchus, arrives at opposition on June 10th, rising around sunset and remaining visible all night long. The grand planet reaches a peak magnitude of -2.6, and telescopes show a generously large disk. The only problem for viewers at mid-northern latitudes is Jupiter’s southerliness (declination -22 degrees) and thus lowness in the sky. For good telescopic views of Jupiter’s cloud belts and zones, look when it’s highest in the middle of the night. At sundown on June 16th, look low toward the east-southeast horizon for the rising moon and situated prominently about 4 degrees to its upper right will be Jupiter. At around midnight, Jupiter will appear to the right of the moon and the gap between them will have widened to 6 degrees. By around 5 a.m., Jupiter is just about to set with the moon now standing 8 degrees to its upper left. Jupiter is slowly retrograding (moving westward) in southern Ophiuchus, pulling closer to the ruddy star Antares sparkling to its right. They’re separated by 13 degrees on June 1st but 8 degrees on the 30th.
Saturn — will likely be the object that everyone with a telescope will want to look at first during the next few months. It rises at the end of twilight by June 8th, and less than a half hour after sunset by month’s end. Like Jupiter, the ringed planet comes to opposition (opposite the sun in the sky) on July 9th, but also like Jupiter, Saturn never gets very high, especially as seen from northern states, due to its southerly declination in Sagittarius, well to the left of the famous Teapot asterism. Even at around 2:30 a.m. local daylight time when Saturn transits the meridian due south, its altitude is less than 30 degrees as seen from mid-northern latitudes. Saturn’s rings are, of course, its leading attraction. Even a 2-inch telescope at 20 power will show them and they are still wide-open to our line of sight, their northern face being tilted 24 degrees to our line of sight. Then there are Saturn’s moons. The brightest, Titan, is within reach of any telescope that shows the rings. Finally, during the overnight hours of June 18-19, watch as the waning gibbous moon interacts with Saturn. As they rise together in the east-southeast, Saturn will be the bright yellow-white “star” shining a little over a degree to the upper left of the moon. At around midnight, Saturn will shining directly above the moon and at the break of dawn it will be positioned to the right of the moon.
Joe Rao serves as an instructor and guest lecturer at New York’s Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers’ Almanac and other publications, and he is also an on-camera meteorologist for Verizon FiOS1 News in New York’s lower Hudson Valley. Follow us on Twitter @Spacedotcom and on Facebook.