In May we lose the two brightest lights in the evening sky: Venus and Sirius, the brightest of stars.
Sirius begins the month very low in the southwest and drops out of sight by mid-month. In the last two weeks of May, most of the other bright winter stars also disappear. Venus, a brilliant evening star, plummets through the sky and is gone by month’s end. Near the end of its fall, Mercury pops into the sky; it passes Venus on May 21, when both are extremely low and in the sun’s afterglow. Venus reappears in the morning sky in July, but then only the early—very early—birds will catch a glimpse of it.
At nightfall Leo, the lion, appears to be leaping downward in the southwest. Look for the bright star Regulus, at the base of a backward question mark of stars called the Sickle; this is the lion’s head. East of Regulus, fairly bright Spica shines from its berth in Virgo, the maiden. Above Spica, radiant Arcturus anchors kite-shaped Bootes, the herdsman.
Jupiter and Saturn rise a couple of hours after midnight on May 1, appearing earlier every morning. Mars follows them by about two hours. All three planets are well up in the southeast before day starts to break.
As the month goes by, Mars climbs steeply but makes little progress westward. Saturn and brilliant Jupiter, however, hurry westward while making only modest gains in altitude. These giant planets are gradually approaching each other, even as they glide steadily farther from Mars. Above Saturn and Jupiter shines the Summer Triangle of bright stars. Altair, in Aquila, the eagle, is the closest to the planets.
May’s full moon will be another big, bright supermoon. Fullness happens at 5:45 am on Thursday, May 7. If you watch it rise the night before or after, it will be close to half a day before or past full. If you go out the morning of May 7, remember to check your local time of moonset. Moonset times range from 5:59 am in Grand Marais to 6:32 am in Pipestone.
May 1 and throughout the month
Comet C/2017 T2 (PANSTARRS) is in the sky throughout the month, and is estimated to reach peak brightness around mid-May, when it’s expected to be visible through binoculars. A finder chart is available here.
The waning gibbous Moon, Saturn, and Jupiter will close together in the early morning sky at around 4 am.
The crescent Moon and Mars will be within a hand length of each other in the early morning sky at around 4:30 am. This is a great time to observe Oceanus Procellarum (the Ocean of Storms), the largest maria (dark region) on the Moon. See how many craters you can spot inside the 1,500 mile wide region!
Stay up late or get up extra-extra early to catch a stunning view of the galactic center in the southern sky at around 2 am. Observing will be easier tonight since the Moon is new, but observing in the days before and after the new Moon are also great times to observe the center of our galaxy.
Deep Sky Objects
Looking at the early evening sky during the beginning of summer we can see a sparse sky, with just a few bright stars filling the emptiness. This may sound disappointing, but don’t despair. This part of the sky is looking away from the bright spiral arms of our Milky Way galaxy, out into extra-galactic space where we can find other galaxies. To hunt these galaxies down you’ll need dark skies and at least a pair of binoculars.
Start by looking high above your head to the west there the Big Dipper still shines bright. The star at the end of the handle of the Big Dipper is named Alkaid, and if you look just a few finger widths below the handle you can spot the magnificent spiral galaxy Messier 51 (M51), or the Whirlpool Galaxy. This is actually a pair of interacting galaxies with the smaller M51b just a few tens of thousands of light-years away from its larger companion.
Next use the Big Dipper and your star map to track down the rest of Ursa Major, the Larger Bear. Once you can see this constellation, move one fist width back from the nose of the bear (towards the tail) and then another fist width above the bear. There, your hard work will be rewarded with the sight of Messier 81, or Bode’s Galaxy. Although M81 is only half the size of the Milky Way—approximately 100,000 light years across compared to the Milky Way’s 200,000—it is one of the closest galaxies to us. At just 12 million light-years away, it’s easily seen with binoculars and, from some observing reports, even the naked eye!
May 7—Full Moon
The Moon is located on the opposite side of the Earth as the Sun and the side we see is fully illuminated.
May 14—Last Quarter Moon
This phase occurs when the Moon is three-quarters of the way through its orbit around the Earth.
May 22—New Moon
The Moon is located on the same side of the Earth as the Sun and is not visible in the night sky. This is the best time of the month to observe faint objects like galaxies and star clusters because there is no moonlight to interfere.
May 29—First Quarter Moon
The Moon is one quarter of its way through its orbit around the Earth, which makes half the Moon illuminated and half dark from our perspective.