With the moon out of the sky for most of the week, skywatchers get to experience dark nights, perfect for exploring stellar giants and enjoying a sprinkle of shooting stars.
Arcturus Shines: Monday, August 5, look west after nightfall for orange-hued Arcturus, the lead star in the kite-shaped, northern constellation Bootes (the herdsman). At 37 light years away, this dying red giant is about 25 times wider than our sun and burns 215 times brighter.
According to Greek mythology, the name Arcturus means “bear guardian,” most likely in reference to its neighboring constellation Ursa Major. You can find the rump of the Great Bear–the seven stars we call the Big Dipper–easily just to the upper right of Arcturus this week.
In 1933 the light of Arcturus was focused through telescopes and used to turn on the floodlights at Chicago’s World’s Fair.
Perseid Shower Begins to Sprinkle. Celestial fireworks begin this week with the famous Perseid meteor shower slowly ramping up in the late night skies. While the peak occurs on August 12, observers should start seeing 5 to 10 shooting stars per hour appear to radiate out from its namesake constellation, Perseus, rising in the northeast horizon in the overnight hours.
Moon Snuggles with Venus. Gaze towards the low west after sunset on Friday, August 9, for a meeting between the crescent moon and the goddess of love. The cosmic pair will appear less than 6 degrees apart–about the width of your three middle fingers at arm’s length.
Altair, the Eagle’s Eye. On Saturday, August 10, look southeast after dark, a little more than halfway from the horizon to straight overhead, for the bright star Altair–the eye of the mythical eagle, Aquila. It is the second brightest star in the familiar Summer Triangle stellar pattern along with Vega and Deneb.
At only 17 light-years away , Altair is about a million times farther than the sun is to Earth, and yet it is still the closest stellar neighbor visible this season.
Astronomers have found one particularly impressive feature with Altair: it rotates 100 times faster than our sun. To put that into perspective, our Earth rotates on its axis once every 24 hours while Altair–which is twice the mass of our sun–takes only 10 hours to spin once around. Its spin rate is so fast that it flattens the star at least 14 percent, making it into a distinctly elliptical shape.