As was the case in April, four of the five brightest planets are visible only in the morning sky. Venus Y Jupiter, emerging from a close conjunction with each other on the last day of April, now begin to separate in May. Still spectacularly close to each other at the beginning of the month, these two stunning ones will be almost 30 degrees apart by the end of the month.
Jupiter will rise higher each morning, becoming much fainter Mars for the 29 Meanwhile, Mars provides the opportunity to make a sighting (with good binoculars and telescopes) of the most distant planet: Neptune — on the 18th, with Mars passing just south of this bluish gas giant. Saturn it is also a morning object, positioned far to the west of Venus, Jupiter, and Mars.
In the evening sky, there is only Mercuryshining low in the west-northwest sky just after sunset and keeping company with the nearby pleiades star cluster, 1st magnitude Aldebaran and, on day 2, a very thin crescent moon. Watch fast, though, because Mercury will fade rapidly during the first week of May, and then it will disappear. When you see it again next month, it will have joined the other four planets in the morning sky.
In our program, remember that when measuring the angular separation between two celestial objects, your clenched fist held at arm’s length measures approximately 10 degrees. Here’s a schedule below that provides some of the best times to see the planet and tells you where to look to see them.
Mercury begins the month by setting in the west-northwest in a dark sky just a few minutes after the end of evening twilight. On May 1, it shines at magnitude +0.7, only slightly brighter than Aldebaran orange and easily a dozen degrees to that star’s lower right. Also, binoculars or a wide-field telescope will reveal the beautiful view of the Pleiades centered just about 2 degrees to the right of this speeding planet.
On the following night, the two-day moon’s thin stripe (4% illuminated) will join the array, sitting 4 degrees to Mercury’s upper left. Telescopically, the planet appears about a quarter bright and in the following days, as its crescent phase thins, Mercury rapidly fades to magnitude +1.6 by the sixth; a couple of nights later the planet can no longer be seen.
Mercury passes through inferior conjunction between the sun Y land on the 22nd and enters the morning sky.
venus and jupiter
Venus and Jupiter pick up where they left off in late April, and continue to turn heads as May begins, mimicking a dazzling “double planet” low in the eastern sunrise sky. The two planets rise around the beginning of sunrise (for mid-northern latitude sky watchers) and will be about 12 degrees high in the east about half an hour before sunrise. In the mornings that follow, Jupiter will move away from Venus, rising to the west, and by the end of the month, the great planet will be rising around 2:30 am daylight saving time. Venus, meanwhile, will continue to rise at dawn, until August.
On the 25th, the Moon it will sit about 5 degrees to the lower left of Jupiter, and Jupiter in turn will sit 2.5 degrees to the left (east) of Mars. On the 27th, the crescent moon will be 3.5 degrees to the lower left of Venus. Finally, on the morning of the 29th, Mars and Jupiter are in conjunction with Mars passing only 0.6 degrees below Jupiter.
Mars rises about 30 minutes before first light in May, as it has every morning since the beginning of the year. However, Mars has since doubled in brightness and has traveled east since ophiuchus through Sagittarius and Capricorn in Aquarius. But the red planet is still not much to look at through a telescope. It is a gibbous ball that even in moderately large telescopes appears as nothing more than an orange speck.
But also on May 18, the red planet will pass 0.5 degrees south of Neptune, providing a good opportunity to identify this more distant planet. With large binoculars or a telescope, Neptune will appear as a tiny bluish “star” only 1/700 as bright as Mars. As noted above, Mars will have a close encounter with Jupiter in the predawn hours of the 29th.
Saturn during this month shines in the southeast in eastern Capricorn as sunrise begins. On May 22, during the early morning hours, you’ll see Saturn shining as a bright yellow-white “star” hovering 5 degrees above the last quarter moon.
Joe Rao is an instructor and guest speaker at New York’s Hayden Planetarium. write about astronomy natural history magazinethe farmers almanac and other publications. Follow us on twitter @Spacepointcom and in Facebook.