Here’s how to see three naked-eye planets visible in June’s night sky.
If there was ever a “Month of the Planets” then June would be it!
Saturn is visible virtually all night long this month, coming to the opposition on June 27th and being accompanied across the sky that night from horizon to horizon by a full moon. Venus reaches its highest point above west-northwest horizon at sundown for 2018 this month. Speedy Mercury can be spied late in the month far to the lower right of Venus. Jupiter dominates the sky after Venus has set, remaining in view for most of the night. And finally, there is Mars which more than doubles in brightness during June as its distance from Earth decreases by half a million miles per day on its way to its closest approach to our planet in 15 years. It pops up above the east-southeast horizon around midnight at the start of June and about 90 minutes earlier by month’s end.
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.
Mercury – reaches superior conjunction on June 6th, passing from the morning to the evening sky. Observers who closely follow Venus may be able to see Mercury as early as the evening of the 13th in rather bright skies, about a half hour after sunset and hovering just above the west-northwest horizon nearly 30 degrees to the lower right of Venus. Mercury, at magnitude -1.4, will then match Sirius (the brightest star) yet will be fainter than Venus by nearly three magnitudes. By month’s end, Mercury dims to magnitude -0.1 but is more easily found, setting 1½ hours after the sun.
Venus – during June appears highest right after sunset for this current evening apparition for those living at mid-northern latitudes, despite the fact that Venus won’t reach the greatest elongation from the sun until mid-August. This is true because the planet is moving rapidly south relative to the sun. This dazzling world (magnitude -4.0) is more than 25 degrees high at sunset now for observers around 40 degrees north latitude. It sets about 2½ hours after the sun at the start of June and maintains this interval throughout the month. You should be able to detect the gibbous phase of Venus in your telescope if the atmosphere is calm and you observe as early in twilight as possible before it has sunk too near the horizon. On June 11th, at dusk, Venus forms a nearly straight and horizontal line, just over 10 degrees long with the much fainter “Twin stars,” Pollux and Castor. On the 16th, a lovely crescent moon and Venus likely will attract attention to even casual sky watchers at dusk, although they are not really all that close to each other; Venus appears 7 or 8 degrees to the right of the moon as they descend the west-northwest sky. On the 19th, Venus is now in the middle of the faint zodiacal constellation of Cancer the Crab. Wait until about an hour after sunset and use binoculars or a wide-field telescope at low magnification to detect big Messier 44, the Beehive Cluster, as a faint sprinkling of stars less than a degree to the lower left of Venus; a lovely sight.
Mars – swings into early-evening view during this month. It kicks off June rising near midnight local daylight time and by month’s end it rises in the southeast at the end of evening twilight. All year Mars has been rising slightly earlier every night and slowly brightening. As Mars’ distance from the Earth decreases from 57 million miles to 42 million this month, the planet more than doubles in brightness from magnitude -1.2 to -2.2, and its nearly full disk grows in apparent size. In fact, by the end of June Mars will appear nearly as bright as Jupiter. When Earth passes Mars late next month (opposition), it will be closer and brighter than it has been for 15 years. Even now it’s a prime attraction for telescopes. On June 3rd, during the predawn hours, take note of Mars, resembling the color of a burning ember, glowing below and to the left of a waning gibbous moon. Note how for the balance of the night, the moon appears to approach Mars at a pace of roughly its own apparent diameter per hour.
Jupiter – was at opposition in early May, so in June it fades ever so slightly to magnitude -2.4 and gets a trace smaller in telescopes. Although Venus outshines it, Jupiter is the dominant light in its part of the sky and still offers a generously big disk; given good seeing and a large telescope, it can be rich in telescopic detail. On the 23rd, as darkness falls, take note of Jupiter in the south-southeast shining to the lower right of a waxing gibbous moon.
Saturn – comes to opposition in grand fashion, being accompanied across the sky by the full moon, which itself also happens to be opposite to the sun. Saturn will arrive at opposition at 8:17 a.m. EDT on the 27th. The moon will pass about 1 degree to its north about 15 hours later and will then officially turn full at 12:53 a.m. EDT on the 28th. Without question, Saturn will be the showpiece planet of the night during the upcoming summer months. But unfortunately, Saturn never gets very high, especially from northern states, due to its southerly declination in Sagittarius. Two hours after rising, Saturn is still no more than 20° above the southeast horizon (depending somewhat on your latitude). Even around 1 a.m. local daylight time when Saturn crosses the meridian due south, its altitude is only around 30 degrees for most of the United States — or to be exact, 68 degrees minus your latitude. By dawn, Saturn has shifted to the southwest. Saturn’s rings are, of course, its leading attraction, currently tilted about 26 degrees to our line of sight, and according to Murray Paulson in the Observer’s Handbook of the Royal Astronomical Society of Canada, are currently visible “. . . even in steadied (or image-stabilized) high power binoculars and small spotting scopes.” But the ball of the planet is a worthy object in its own right. It is the second largest planet after Jupiter and shows similar atmospheric features, though they are smaller and much paler. Then there are Saturn’s moons. The brightest, Titan, is within reach of any telescope that shows the rings. It will appear farthest west of Saturn on June 7th and 23rd and farthest east on June 15th and July 1st