The Double Double: Detach Lyra’s multiple-star gem

Epsilon Lyrae, the famous “double double” multiple star, lies close to brilliant Vega. A graphic by Greg Smye-Rumsby.

Epsilon (ε) Lyrae is a flagship multiple star for binocular enthusiasts, known as the “Double Double”. It’s a difficult target to divide with the naked eye, as it appears as a fairly close binary of closely spaced fifth magnitude stars. Epsilon is beautifully transformed even through a small telescope, showing that each star is itself a double! Together with the trapezium in Orion, it is probably the best multiple star ever.

Epsilon Lyrae is split into a multiple star system by a small telescope operating at medium to high power on a steady, transparent night. Sketch: Jeremy Perez.

How to observe

The double double is very easy to locate, lying just 1.6 degrees northeast of blazing Vega (magnitude +0.03), the fifth brightest star in the entire sky. epsilon1 Lyrae (magnitude +4.67) lies to the north (also slightly west; position angle [PA] ~350°) from Epsilon2 Lyra (+4.59). The pair are separated by 3.5 inches, an easy task to separate through binoculars, although you’ll need an excellent night and keen eyesight to see them as two stars without optical aid.

On a calm and clear night, swing a small telescope in the epsilon direction and at medium to high magnification you should be able to dissect both stars into their component parts. Observers report that a scope with an aperture as small as 60mm (~2.4 inches) can get the job done, but nighttime visibility conditions are probably the determining factor in how big a scope you need.

epsilon1 (STF 2382) splits into binary components (A and B) of magnitudes +5.2 and +6.1 that lie 2.2 inches apart in an approximate north-south alignment (PA 347°). The stars have an orbital period of about 1,800 years. epsilon2 (STF 2383) consists of +5.3 and +5.4 magnitude (C and D) stars spaced 2.3 inches apart at a PA of 79° (nearly east-west). It takes them around 700 years to complete one orbit. All stars are class A white stars.

The Double Double pictured by Damian Peach. The Double Double: Detach Lyra’s multiple-star gem

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