Stellar Vista Observatory Sky Report
Sept. 13 – 19
The Sky Report is presented as a public service by the Stellar Vista Observatory, a nonprofit organization based in Kanab, Utah, which provides opportunities for people to observe, appreciate, and comprehend our starry night sky. Additional information is at www.stellarvistaobservatory.org. Send questions and comments to [email protected]
Beginning with planets, the first to appear as darkness falls is Venus, in the southwest. At the moment of sunset it’s 18 degrees above the horizon, as seen from Kanab, and you can spot it with binoculars. An hour later it’s only 7 degrees high and you may need to peer between buildings or trees to see it.
Little Mercury is to the lower right of Venus. Although it’s at its greatest angular separation from the sun (27 degrees) on Monday, it’s even lower and too faint to see it easily as explained in the Sky Report two weeks ago.
But do look at Jupiter and Saturn, especially if you have a telescope – or access to one. Jupiter is the brightest object in the southeast and Saturn is 17 degrees straight to its right (remember that your fist held at arm’s length spans 10 degrees).
Tripod-mounted (or image-stabilized) binoculars with at least 10 times magnification will show Jupiter’s four large moons but probably not Saturn’s largest moon Titan; the rings require a minimum of 30 power. The moon passes them this week, standing directly below Saturn on Thursday and below Jupiter on Friday.
The bright star that is virtually overhead once the sky is dark is Vega, in the small constellation Lyra, the lyre – a type of primitive harp popular in ancient Greece. Vega is 26 light years distant which makes it one of the nearer bright stars. It’s 50 times as bright as our sun; if you placed our sun next to Vega it would be barely visible to the naked eye.
Vega is the topmost of three equally-bright stars that form the popular Summer Triangle. The other two are Deneb, to the lower left of Vega, and Altair, considerably lower and to the right, halfway to Saturn. They are in the Swan and Eagle respectively.
The gravitational attraction of the moon and sun cause the spinning earth to wobble, or precess, like a toy top that is slowing down before it falls over. It takes the earth 26,000 years to complete one wobble, and during that time the earth’s axis, which points to the sky’s north pole, makes a huge circle in the sky. Today the axis points to Polaris, our current North Star, but in 12,000 years it will point near Vega and Vega will be our North Star. Google “precession of the equinoxes.”