Lyra

by Shaphan Shank | Aug 1, 2022 | 0 comments

Ring Nebula
Ring Nebula. Photo © NASA, ESA, and the Hubble Heritage (STScl/AURA)-ESA/Hubble Collaboration.

Lyra, the Harp, is a small constellation that lies almost straight overhead on August evenings in the mid-northern latitudes. Lyra is outlined by just five stars. Four of them form a parallelogram, and the fifth extends from one corner of this parallelogram. This fifth star, Vega, is the brightest star that lies high overhead in the Northern Hemisphere sky during late summer. Lyra is quite easy to find due to its distinctive shape and the brilliance of Vega.

Despite its diminutive size, Lyra contains several outstanding telescopic targets. One of the most well-known of these targets is Epsilon Lyrae, a pair of double stars that is commonly known as the Double Double. The Double Double lies just under 2° northeast of Vega.

The two star pairs that make up the Double Double lie so close together (3.5 arcminutes) that they look like a single star at first glance. However, if you have sharp eyes, you should be able to split this “star” into two little pinpoints of light with your unaided eyes. A telescope at high magnification shows that both of these stars are doubles themselves. The two pairs that make up the Double Double are nearly identical. Both consist of white stars of nearly equal magnitude, separated by about 2.5 arcseconds. The only apparent difference between the pairs is that they are oriented perpendicularly to each other.

Epsilon Lyr is among the most famous multiple star systems in the sky, but few people are aware that there is a second double double star in Lyra. The two doubles that make up this second pair are known as Struve 2470 and Struve 2474. These two doubles are separated by about 10.5 arcminutes, three times the separation of the pairs that make up Epsilon Lyr. Struve 2470 and 2474 are just faint enough to be invisible to the unaided eye, but they are easily visible with binoculars. To find them, take a line from Vega to Delta Lyr, then continue the same distance again beyond Delta Lyr. The end of your line will be very near Struve 2470/2474.

The first thing you will notice about Struve 2470 and 2474 is that they are much easier to split than the pairs that make up Epsilon Lyr. They are also a little more colorful than the all-white pairs of Epsilon Lyr. The components of Struve 2470 are white and blue-white, while the components of Struve 2474 are yellowish. The secondary stars of both pairs are a little dimmer than the primary stars, and the pairs are oriented in the same direction instead of perpendicular to each other like the pairs that make up Epsilon Lyr.

Along with its doubles, Lyra contains one of the finest planetary nebulae in the sky. M57, the Ring Nebula, lies about halfway between Sulafat and Sheliak, the two stars that make up the southern end of Lyra. The Ring Nebula is bright enough that it is easy to spot in any good-quality telescope, although you will get the best views of it with a large telescope. The Ring looks like a slightly elongated smoke ring, with one end a little more pointed than the other. The center of the nebula is filled with faint nebulosity. This nebulosity is not obvious, but, with a mid-sized telescope, you should be able to tell that the center of the nebula looks a little different from the surrounding sky.

Star map of Lyra, Vulpecula, Cygnus, Hercules

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