You are here: Home USNO News, Tours & Events Sky This Week The Sky This Week, 2016 July 26 - August 2

The Sky This Week, 2016 July 26 - August 2

Gliding through the Milky Way.
M22_140705_01small.jpg
Globular Star Cluster Messier 22 and Milky Way star field
imaged 2014 July 5 from Morattico, Virginia

The Moon wanes through her crescent phases in the pre-dawn sky this week as she wends her way into the rising stars of late autumn and early winter. New Moon occurs on August 2nd at 4:45 pm Eastern Daylight Time. Watch the Moon glide through the Hyades star cluster, the scattered group of stars around the bright star Aldebaran, during the hours before sunrise on the 29th. By 5:30 am the star will be less than half a degree from Luna’s bright limb. If you watch the pair with binoculars or a small telescope, watch Aldebaran disappear behind the bright limb at 6:06 am EDT, coincident with sunrise here in the Washington area. The star will re-appear from behind the Moon’s dark limb at 6:53 am.

Assuming you can find a spot away from city lights and from the humidity and heat we’ve been experiencing lately, this is a great week to explore the wonders of the summer sky. To me the greatest of these is the ghostly shimmering band of light that delineates the summer Milky Way. It’s always a highlight of summer vacation to spend time out under this misty apparition with a pair of binoculars slowly sweeping across its mottled glow. What appears to the naked eye as a formless glow begins to resolve into clouds of innumerable stars laced with dark spots and rifts. Summer is the best time for those of us in the Northern Hemisphere to see the brightest parts of our home galaxy since its densest star clouds, which lie between us and the galaxy’s center, dominate the southern reaches of the sky from near the zenith to the horizon. The galaxy’s center, located some 30,000 light-years from us, is buried behind successive clouds of stars and dust that delineate the spiral arms and lies in the general direction of the "spout" of the "teapot" asterism in the constellation of Sagittarius. Scattered through the Milky Way are dozens of star clusters and bright emission nebulae that you can see in binoculars. Many of these will yield to the small telescope as resolved clusters of many stars, offering some of the best views of deep-sky objects for very modest scopes. As you follow the Milky Way toward the north, you’ll notice that it bisects an asterism of three first-magnitude stars that are known as the Summer Triangle. Each of the stars lead a separate constellation, and one of these is the focus of the current observing campaign for the international Globe at Night citizen-science program. The star Deneb, faintest of the three Triangle stars, denotes the "tail" of Cygnus, the Swan, which is the target for this month’s observing campaign.

This week offers one of those rare times when we can see all five of the planets visible to the unaided eye at the same time. To catch two of them you’ll need binoculars and a clear view of the western horizon, but you’ll be looking for one of the brightest objects in the sky in the form of Venus, which is a few degrees above the horizon about 20 minutes after sunset. About six degrees to the left of Venus you should see the glow of Mercury, which shares the field of view with the star Regulus in Leo. Mercury will be less than half a degree from the star on the evening of the 30th. Both Venus and Mercury will appear in the same relative configuration for the duration of the week and will be joined by a very slender crescent Moon on the evening of the 3rd.

Jupiter is still easy to spot during the twilight hours, but his time in the evening sky is short. The giant planet now sets just after the end of evening twilight, so if you want to get a look at him through the telescope you’d better act fast.

Mars is now marching steadily eastward against the stars, closing the nightly gap between himself and the star Dschubba, the middle star in the "head" of Scorpius. By the week’s end the star and planet are just two degrees apart. Mars is still easy to find in the evening sky thanks to his distinct ruddy glow. His telescopic disc now shows a very pronounced gibbous phase.

Saturn lies just west of the meridian at 9:30 pm, and forms a triangle with bright Mars and the bright star Antares. Of all the planets that currently inhabit the sky, Saturn provides the most rewarding view through the telescope. The planets rings provide the "wow-factor" at any star party, and if you’re like me you’ll never tire of looking at him on these warm summer nights.

USNO Master Clock Time
Javascript must be Enabled