Epsilon Lyrae -- The Double Double
Binary Star System
aka 4 Lyr, HR 7051, HD 173582, HIP 91919, BD +39 03509, ADS 11635, CCDM 18443+3938, TYC 03122-3438 2, GSC 03122-3438
RA: 18h44m18.5s Dec: +39°40'13" (Lyra)
Integrated Visual Magnitude: 4.7
Distance: 160 +/- 6.1 ly

Minimum requirements to detect: any telescope


Epsilon Lyrae is one of the most observed multiple star systems and makes for a great view in just about any telescope, under even the most light polluted skies.  It is easy to find as one of bright stars in the tiny constellation of Lyra.  For these reasons it is a great object for beginners to cut their teeth on.  Make sure to look when the pair is high in the sky, and if the view is blurred by the atmosphere, turning the wider pair of stars in large blobs, wait for another time.

Rather than a singe bright pair of stars Epsilon Lyrae splits into two pairs, Epsilon1 and Epsilon2.  Epsilon1 is the northern pair which is on the right in the diagram above.  Shown are two stars of 4.7 and 6.2 magnitude currently separated by 2.6" at position angle 350o. These stars are physically connected, orbiting slowly about their common center of gravity in a cosmic dance.  It probably takes something on the order of 1200 years for them to complete one orbit.

Epsilon2 (left) consists of 5.1 and 5.5 magnitude stars currently separated by 2.3" in position angle 82o.  They are also physically connected, orbiting once every 585 years.

All of the stars appear off-white in the eyepiece.

Remarkably, each pair is also physically connected to the other.  Separated by 0.16 light years they would take hundreds of thousands of years to complete an orbit.  The pairs themselves are separated by 208" in position angle 173o. Binoculars may show the widely separated  pairs as two stars and some keen-eyed observers may be able to discern them with their eyes alone.

The view in a 6 inch at 270x.  North is down and east is to the right.

Millennium Star Atlas Vol III Chart 1132
Sky Atlas 2000 Chart 8
Uranometria 2000 Vol I Chart 82
Herald-Bobroff Astroatlas B-05 C-21

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