This month the great planet race continues, as Venus, Mars and Saturn form a triangle in the west. Watch the triangle change shape each night as Venus overtakes Saturn and then Mars!
Venus is by far the brightest of the three planets. Face west at dusk and look for a point of light that outshines everything in the night sky.
Saturn and Mars are to the upper left of Venus as August opens. Mars is below Saturn and a bit to its left. Although these two planets of similar brightness are much dimmer than Venus, they outshine all the other stars near them.
Observe all three carefully throughout August and watch as their configuration changes. Mars aligned with Saturn last Saturday (July 31) and now begins to move farther to Saturn’s left. Venus, moving faster than the other two, continues to approach from the right; it will pass Saturn on August 8. Venus then continues to gain on Mars as they both move away from Saturn. Venus finally overtakes Mars on August 19-20. On the night of August 31, Venus and Mars are to either side of the star Spica in Virgo.
Jupiter is now a late evening object, rising by 11 p.m now and by 8:45 p.m. at month’s end. It outshines all stars in the sky, so it’s easy to find. Face east in late evening or south southwest at dawn to see it.
The Big Dipper is in the northwest at dusk. You can extend the curve of its handle to ‘arc to Arcturus’ and then ‘speed on to Spica’. These stars are in the west at dusk tonight. Arcturus, by the way, is the fourth brightest star we ever see at night, but the brightest one Americans ever see on an August evening. Spica is in Virgo, the constellation where this month’s ‘planet race’ occurs.
In the east, look for the enormous Summer Triangle, consisting of the stars Deneb, Vega, and Altair. This triangle is up all night long from June to early August, hence its name. Scorpius, the Scorpion, is in the south at dusk. Sagittarius, the Archer, known for its ‘teapot’ asterism, is to its left. Between these two star patterns is the center of our Milky Way—the brightest part of that band as wee see it. On a cloudless night far from the big city, see if you notice the Milky Way glow near the ‘teapot’ of Sagittarius. In late evening, look for the Great Square of Pegasus rising in the east.
Moon Phases in August 2010:
Last Quarter August 3, 12:00 a.m.
New Moon August 9, 10:08 p.m.
1st Quarter August 16, 1:14 p.m.
Full Moon August 24, 12:05 p.m.
On Friday morning, August 13, the Earth passes through a stream of debris left long ago by Comet Swift-Tuttle. This produces the Perseid Meteor Shower, one of the best meteor showers each year. The Perseids occur every year at about this time, producing on average about one meteor per minute. Keep in mind that even a short period such as a minute can seem longer if you are waiting for something to happen. Since Earth is running into the meteors, not the other way around, the leading edge of the Earth encounters the shower. This is the side going from night into day. Accordingly, we see more meteors as dawn approaches. Big city lights or the Moon can limit the meteors you see by dimming out fainter ones. This August, however, the New Moon is on the 10th, giving us a skinny crescent on the 12th which sets long before the shower really gets going. The main challenge, then, is to avoid city lights.
If skies that night are clear, our George Observatory will open Thursday night, August 12 at 9pm and remain open until dawn for observing the shower. If you come out to George or go elsewhere, you’ll want to lie on your back (to see as much of the sky as at once as possible) and orient yourself towards the constellation Perseus. (The shower is called the ‘Perseids’ because they seem to radiate from that constellation.) Perseus rises in the northeast at dusk and is high in the north at dawn.