Aug 01

What’s Up in the Sky

What’s Up in the Sky – August, 2013

August is always a good month for observing and next month is doubly so. I have two challenges for dedicated readers. First,, observe the Perseid meteor shower for at least two hours, and second, find at least three double stars.

As with any meteor shower, the best viewing occurs in the hours just before dawn, but most people prefer an earlier viewing experience. My advice is to take a nap after dinner Sunday, August 11, so you can set up your lawn chair, bundle up in a sleeping bag, and sit back and enjoy the show starting around midnight. No optical aid (such as a telescope) is required or even desirable – this is a naked-eye observation. Depending on how clear and dark your sky is, you could see up to 50 or 60 meteors per hour. Don’t get discouraged if you only see a few at first. The rate should increase as time goes on and your eyes become dark-adapted.

Start your double star search with Mizar, the middle star in the handle of the Big Dipper, found in the northwest sky around 10 p.m. Look closely and you will notice Mizar has a faint companion, known as Alcor. In a small telescope you can see what was first observed in 1650 – Mizar itself is a double star, its two components close, but easily separated.

In contrast, it was not until 1889 that astronomers, using a spectroscope, discovered that Mizar’s brighter component consisted of two stars, making it the first binary to be discovered by spectroscopic methods. Years later the other component was also shown to be a spectroscopic binary, making Mizar a quadruple star.

I used to teach that Alcor and Mizar make up what is known as a visual double. That is, they are not gravitationally bound to each other, but merely lie almost in the same direction of sight and therefore appear close to each other. In 2009 researchers reported strong evidence indicating that not only was Alcor also a spectroscopic binary, but also that it is indeed gravitationally bound to the Mizar system. So, when you look at the famous double in the handle of the Big Dipper, you are actually looking at six stars. How cool is that?

Next check out the star at the very bottom of the Northern Cross and the one right next to Vega (called Epsilon Lyrae). These are both nearly overhead and thus perfect for a small Dobsonian telescope. I will let you discover how cool these guys are.

All in all, this should be a good month to enjoy what’s up in the sky.

This month in history:
August 2: First televised liftoff of lunar module – Apollo 15’s “Falcon” – 1971
August 5: Neil Armstrong born – 1930
August 12: Echo 1 launched – 1960
August 20: Voyager 2 launched – 1977
August 25: Voyager 2 flies past Saturn – 1981
August 27: Teacher in space program announced – 1984