Epsilon Lyrae

Starbox begin
name = Epsilon LyraeStarbox observe 2s
epoch = J2000.0
equinox = J2000.0
constell = Lyra
component1 = Epsilon¹ Lyrae
ra1 = RA|18|44|20.3453
dec1 = DEC|+39|40|12.444
appmag_v1 = 1.18
component2 = Epsilon² Lyrae
ra2 = RA|18|44|22.7803
dec2 = DEC|+39|36|45.798
appmag_v2 = 1.10Starbox character
class = F1V / A8V
r-i =
v-r =
b-v =
u-b =
variable = Starbox astrometry
radial_v =
prop_mo_ra =
prop_mo_dec =
parallax = 20.10
p_error = 0.76
parallax_footnote =
dist_ly =
dist_pc =
space_v_u =
space_v_v =
space_v_w =
absmag_v = Starbox catalog
names = 4 Lyr, HR 7051, HD 173582, HIP 91919, BD +39 03509, ADS 11635, CCDM 18443+3938, TYC 03122-3438 2, GSC 03122-3438 Starbox reference
Simbad = eps01+Lyr
ARICNS = Starbox reference
Simbad = eps02+Lyr
ARICNS =

Epsilon Lyrae (ε Lyr / ε Lyrae), commonly quoted as The Double Double, is a binary system approximately 162 light-years away in the constellation of Lyra. 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 ε¹ and the southern one is called ε²; 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. [http://www.astro.uiuc.edu/~kaler/sow/epslyr.html]

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.

See also

* HD 98800

External links

* [http://www.skyhound.com/sh/archive/jul/HR_7051.html Epsilon Lyrae -- The Double Double]
* [http://www.daviddarling.info/encyclopedia/E/Epsilon_Lyrae.html Epsilon Lyrae]