Epsilon Lyrae

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Epsilon Lyrae
Epsilon Lyrae is located in 100x100
Epsilon Lyrae
ε (circled) in the constellation Lyra.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Lyra
Epsilon1 Lyrae
Right ascension  18h 44m 20.34589s[1]
Declination +39° 40′ 12.4533″[1]
Apparent magnitude (V) 4.66[2]
Epsilon2 Lyrae
Right ascension  18h 44m 22.78056s[1]
Declination +39° 36′ 45.7851″[1]
Apparent magnitude (V) 4.59[2]
ε1 Lyr
Spectral type A3V + F0V[3]
U−B color index +0.065[2]
B−V color index +0.16[2]
ε2 Lyr
Spectral type A6Vn + A7Vn[3]
U−B color index +0.075[2]
B−V color index +0.18[2]
ε1 Lyr
Radial velocity (Rv)−31.20 ± 1.7[4] km/s
Proper motion (μ) RA: 11.09[1] mas/yr
Dec.: 61.39[1] mas/yr
Parallax (π)20.10 ± 0.76[1] mas
Distance162 ± 6 ly
(50 ± 2 pc)
ε2 Lyr
Radial velocity (Rv)−24.40 ± 1.7[5] km/s
Proper motion (μ) RA: 6.18[1] mas/yr
Dec.: 50.42[1] mas/yr
Parallax (π)20.97 ± 0.50[1] mas
Distance156 ± 4 ly
(48 ± 1 pc)
Other designations
ADS 11635, WDS 18443+3940
ε1 Lyr: 4 Lyrae, HIP 91919, HD 173582, HR 7051, BD+39° 3509, SAO 67310
ε2 Lyr: 5 Lyrae, HIP 91926, HD 173583, HR 7052, BD+39°3510, SAO 67309
Database references
ε1 Lyr
ε2 Lyr

Epsilon Lyrae (ε Lyr, ε Lyrae), also known as The Double Double,[citation needed] is a multiple star system approximately 162 light-years away in the constellation of Lyra.

Star System[edit]

The widest two components of the system are easily separated when viewed through binoculars, or even with the naked eye under excellent conditions.[6] The northern component 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 sets of 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 separated by 2.6" 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 separated by 2.3", and orbit in perhaps half that period. ε1 and ε2 themselves are not closer than 0.16 light years apart, and would take hundreds of thousands of years to complete an orbit. An observer at one pair would see the other pair shining with the light of a quarter Moon (which is about mv = −5.0), less than a degree away from each other.[7][8]

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.

A number of other nearby stars may also be part of the system, bringing the system to a total of ten stars. The arrangement of the system is summarised in the tables below.

Stars in the system
Magnitude Spectral Type
A 5.02 A2
B 6.02 A4
C 5.14 A3
D 5.37 A5
E 11.71
F 11.2
G 13.83
H 13.22
I 10.43
a 10.43


Orbit pairs
Most Recent
Position Angle
Semi-major axis
AB-CD 208.2 10,500 172 ε12
AB 2.3 116 347 1804.41 4.742 components of ε1
CD 2.4 121 79 724.307 2.92 components of ε2
Ca 0.1 5 225 recently discovered
interferometric companion
AI 149.6 7500 138
CE 63.7 3200 333
EF 46 2300 37
EG 50 2500 238
GH 35 1800 358


See also[edit]


  1. ^ a b c d e f g h i j van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. ^ a b c d e f Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Bibcode:1986EgUBV........0M.
  3. ^ a b Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement. 95: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
  4. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  5. ^ Kharchenko, N. V.; et al. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776.
  6. ^ a b c Burnham, Robert (1966). Burnham's Celestial Handbook. Dover Publications Inc. pp. 1151–1153. ISBN 0-486-24064-9.
  7. ^ Jim Kaler. "Epsilon Lyrae". Kaler's Stars. Retrieved 18 November 2013.
  8. ^ http://observing.skyhound.com/archives/jul/HR_7051.html
  9. ^ a b "Washington Double Star Catalog". Retrieved 19 December 2010.
  10. ^ "Sixth Orbit Catalog". Retrieved 19 December 2010.

External links[edit]