Epsilon Lyrae
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation (pronunciation) |
Lyra |
| Right ascension | 18h 44m 18.5s |
| Declination | +39° 40' 13" |
| Apparent magnitude (V) | 1.18 (ε1), 1.10 (ε2) |
| Characteristics | |
| Spectral type | F1V (ε1), A8V (ε2) |
| Other designations | |
| Database references | |
| SIMBAD | make query |
Epsilon Lyrae (ε Lyr / ε Lyrae) is a binary star in the constellation Lyra. Commonly known as the double-double, Epsilon Lyrae is one of the most well known of binary stars. It can easily be separated into two components when viewed through binoculars, or even with the naked eye under excellent conditions. The northern star is called epsilon-1 and the southern one is called epsilon-2; they both lie around 162 light years from Earth and orbit each other. When viewed at higher magnifications, both stars of the binary can be further split into binaries; that is, the system contains two binary stars orbiting each other. Being able to view the components of each is a common benchmark for the resolving power of telescopes, since the individual doubles are so close together: the stars of ε1 were 2.35 arc-seconds apart in 2006, those of ε2 were separated by about the same amount in that year. Since the first high-precision measurements of their orbit in the 1980s, both binaries have moved only a few degrees in position angle.
The component stars of ε1 have magnitudes of 4.7 and 6.2 and have an orbital period that can only be crudely estimated at 1200 years, which places them at roughly 140 AU apart. The component stars of ε2 have magnitudes 5.1 and 5.5, and orbit in perhaps half that period. ε1 and ε2 themselves are no closer than 0.16 light years apart, and would take hundreds of thousands of years to complete an orbit. An observer at either pair would see the other pair shining with the light of a quarter Moon, less than a degree away from each other.[1]
A fifth component of this system, orbiting one of the ε2 pair, was detected by speckle interferometry in 1985 and confirmed in two subsequent observations. No orbit can be prepared from such limited data, but its rapid motion suggests a period of a few tens of years. Its maximum observed separation of 0.2 arc-seconds precludes direct visual observation.
