Astronomy: The Week Ahead – Sun 2 Aug to Sat 8 Aug 2015

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Sunday August 2

The Moon attains perigee at 03:11 today, its closest point to Earth during this lunar month. In a waning gibbous phase it is nearly 18 days old with 89% illumination. You can watch it rise just before 10 p.m. in Aquarius over the eastern horizon.


Monday August 3

The eastern morning sky an hour before sunrise features many familiar winter constellations. And today the planet Mars wanders in among them, shining red low on the horizon. Can you find it before dawn washes it out? If you do, compare its color to the giant red stars Aldebaran in Taurus, and Betelgeuse in Orion.

Mars is in Gemini, shining at a bright magnitude 1.70, around 239 million miles from us.


Tuesday August 4

Get your binoculars out and look due south above the stinger of Scorpius tonight, to find Messier 6 (M6), The Butterfly Cluster. This open cluster is visible without optical aid from even reasonably dark locations, at a bright magnitude 4.2. It is 33 arcminutes in size, comparable to the angular size of the full Moon. At 1,600 light years distance, imagine how brilliant these young stars would be were they the distance of some of our brightest neighbors in the sky! Although their discovery is officially attributed to Giovanni Battista Hodierna in 1654, it is very reasonable to believe Ptolemy saw it, and its neighbor M7 (The Ptolemy Cluster) in the First century.


Wednesday August 5

After Pisces has risen, look for the waning gibbous Moon, then, with binoculars, less than two degrees away you’ll find the green-toned planet Uranus at magnitude 5.8 very nearby the magnitude 5.1 star Zeta Piscium. The Moon is 384,399 km distant, Uranus 1.8 billion miles from us, and Zeta 148 light years away. Zeta is an optical double star (not a binary), with its components 23 arcseconds apart.


Thursday August 6

Tonight is last quarter Moon, rising after midnight at 00:26. It is a good weekday night for deep-sky observing, and if not for the Moon we’d be looking for the Southern Iota Aquariid Meteor Shower. If you still want to try for some meteors, here is the radiant, where this shower will appear to emanate from. Expect 7-8 meteors an hour, averaging magnitude 3.


Friday August 7

The constellation name Lacerta is Latin for Lizard. This is a small and faint constellation created by Polish astronomer Johannes Hevelius in 1687. You’ll find it along the Milky Way between the W of Cassiopeia and Cygnus (the northern cross). Its brightest star, Alpha Lacertae, is a dim magnitude 3.76, so this constellation is a challenge to discern. See if you make out its zigzag shape.


Saturday August 8

Located between Cor Caroli in Canes Venatici, and Arcturus in Bootes, M3 is a bright and easy globular cluster to see in binoculars and any telescope. Arcturus is found by taking the handle of the Big Dipper and making an “arc to Arcturus”. Similarly, you can use the dipper’s handle to make a right angle to Cor Caroli. The cluster will be visible easily in binoculars or a finderscope, slightly closer to Arcturus than the halfway point to Cor Caroli. M3 is 16 arcminutes in size, large for the northern hemisphere, and shines at magnitude 6.19 at a distance of 33,000 light years. This is an impressive cluster of over 500,000 stars!

Happy viewing!