Archive for August 20th, 2009


Mission 3: Waxing Lyrical

August 20, 2009

Mission Objectives: Constellation, Multiple stars

Equipment: Naked eye, Binoculars

Required Time: 3 minutes

Related Missions: Summer Triangle

Instructions: Ready for another constellation? This one is a piece of cake: nice and compact, all bright stars that show up easily even in the city, two simple shapes, high enough to be seen clearly throughout the Northern Hemisphere, and it even has a couple of nice Easter eggs for binoculars and small scopes. I’m talking about the constellation Lyra, the Lyre.

You remember how to find Vega, I’m sure (if you’ve forgotten, refresh your memory here). This time of year it is the brightest star overhead in the early evening; in fact, it is the fifth brightest star in the sky. It is so bright mainly because it is so close, only 25 light years away, not because it is big, although it is about twice the mass of the sun. Because it is heavier it is burning through its fusion fuel faster, and it will swell into a red giant in perhaps half a billion years. By comparison, the sun is only about halfway through its 10 billion year lifespan.

The constellation Lyra (red lines), and the Double Double (white arrow), from Stellarium.

The constellation Lyra (red lines), and the Double Double (white arrow), from Stellarium.

You already know that Vega is at the apex of the Summer Triangle. Even with the naked eye and under city lights, you should be able to see that Vega is also one point of a much smaller triangle, and that the smaller triangle has a parallelogram hanging off its southeast corner. That’s it, the constellation Lyra. If you can find the triangle and the parallelogram, you’re done.

But wait–there’s more! If you’re very sharp-eyed–or your corrective lens prescription is up-to-date–you may be able to see that the star at the “free” corner of the triangle is not one point of light, but two close together. This is Epsilon Lyrae, the famous “Double Double” star. It’s called the Double Double because both of the two stars that make up the naked-eye binary are themselves binary; so, two pairs of binary stars, circling each other. As if that wasn’t enough, spectrometry shows that the system includes a fifth star that is too dim for even telescopes to see.

If you can’t split Epsilon Lyrae into two components with the naked eye, grab your binoculars–any binoculars. Binoculars will show the wide separation between the two pairs, but to split the four visible stars requires a telescope with good optics. At 96x in my 90mm Maksutov-Cassegrain scope, the two pairs look like a couple of 8s, one standing up and one laying on its side. For a much better view, check out this photo of the four stars by acclaimed astrophotographer Damian Peach.

And as long as you’ve got your binoculars out, you might as well have a look at the third “star” in the triangle, Zeta Lyrae (the one star shared by the triangle and the parallelogram). This one is a simple double, not a Double Double, and the two component stars are much closer together than the double-eights of Epsilon Lyrae. Using my 10×50 binoculars and bracing my arms on the top of my car, I just make out that Zeta Lyrae is indeed two points of light, but I can’t hold the binoculars steady enough freehand. About time for a post on mounting binoculars, methinks.



August 20, 2009

Mt Wilson 60 inch 800

Jupiter from Mt Wilson 800

Up far too late, but I couldn’t turn in without posting these. Full report to follow. I took both photos with my Nikon Coolpix 4500. That’s Io next to Jupiter, by the way.