Epsilon Lyrae (ε¹ & ε² Lyrae — The Double Double)
Coordinates, Gaia DR3 distance (160 ly), 208″ wide pair and 2.3″/2.4″ tight sub-pairs, and telescope resolution test guide for Epsilon Lyrae.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Combined apparent visual magnitude | 3.82 mag | ± 0.02 mag | Integrated photometry (ε¹ = 4.67 mag, ε² = 4.59 mag) | definitive | Hipparcos New Reduction Catalog |
| System distance (Gaia DR3) | 49.1 pc | ± 0.4 pc | Gaia DR3 astrometric parallax of components (~20.37 mas, 160.1 ly) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Wide ε¹–ε² angular separation | 3.47 arcmin | ± 0.01 arcmin | Astrometric separation 208.2 arcseconds (tight pairs are 2.3″ and 2.4″) | definitive | ESA Gaia Archive — Data Release 3 |
| Component effective temperatures | 8200 K | 7300 to 8500 K | A3–F0 main-sequence spectroscopy across four visual components | high-confidence | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Epsilon Lyrae (The Double Double Star) at RA 18h 44m 20.30s, Dec +39° 40′ 12.4″ within Lyra, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
Epsilon Lyrae (ε¹ and ε² Lyrae, the 'Double Double'), situated just 1.8° northeast of brilliant Vega, is the quintessential hierarchical quadruple star system for testing telescope optics and atmospheric seeing. To sharp unaided eyes or binoculars, Epsilon Lyrae splits along a north-south line into two 4.6-magnitude stars—ε¹ Lyrae (4 Lyrae) on the north and ε² Lyrae (5 Lyrae) on the south—separated by 208.2 arcseconds (3.47 arcminutes).
When William Herschel examined both stars under higher magnification in August 1779, he discovered that each component is itself a tight binary: northern ε¹ Lyrae splits into magnitudes 5.02 and 6.02 separated by 2.3 arcseconds (orbital period ~1,800 years), while southern ε² Lyrae splits into two nearly equal 5.25 and 5.38 magnitude A-type dwarfs separated by 2.4 arcseconds (orbital period ~724 years).
Remarkably, the position angles of the two tight pairs are oriented nearly perpendicular to each other (~346° vs ~77°), creating an unmistakable geometry in the eyepiece. Speckle interferometry has also detected a fifth star (ε² Lyrae Ca) orbiting one of the southern components, making the system at least quintuple at a Gaia DR3 distance of 49.1 ± 0.4 parsecs (160 light-years).
Practical Visual Observing Guide
- Form an equilateral 1.8° triangle with Vega (α Lyrae) and Zeta Lyrae (ζ Lyrae) at the northern tip of Lyra.
- Binoculars easily separate the wide 208-arcsecond pair (ε¹ and ε²), and observers with 20/20 vision under dark skies can split them with the naked eye.
- By Dawes's limit (116 / D_mm), a 60 mm telescope has a theoretical resolution limit of 1.93″ and can just split both 2.3″ and 2.4″ pairs at 120×–150×; in an 80–150 mm telescope at 150×–200×, all four white Airy disks appear with clean black sky between them in one field of view.
Catalog Cross-Identifications & Aliases
Common Aliases: ε Lyrae · Double Double · 4 & 5 Lyrae · HIP 91919 / HIP 91926
| Catalog Authority | Identifier |
|---|---|
| HIP | HIP 91919 |
| HD | HD 173582 |
| SIMBAD | * eps01 Lyr |
| WIKIDATA | Q13237 |
Related Objects, Comparisons & Guides
Vega (Alpha Lyrae Zero-Point Star)
Coordinates, distance (25.04 ly), magnitude 0.03 photometric zero point, rapid oblate rotation, and observing guide for Vega in Lyra.
Albireo (Beta Cygni Color Double Star)
Coordinates, Gaia DR3 parallaxes of Beta Cygni A & B, 34.6″ angular separation, color contrast, and observing guide for Albireo in Cygnus.
Mizar & Alcor (Zeta Ursae Majoris System)
Coordinates, Hipparcos/VLBI distance (82.8 ly), 11.8′ naked-eye pair, 14.4″ Mizar A–B split, and observing guide for Mizar & Alcor.
Castor (Alpha Geminorum Sextuple System)
Coordinates, Hipparcos distance (50.8 ly), 5.6″ A–B binary orbit, YY Geminorum eclipsing pair, and observing guide for Castor.
Splitting Bright Double & Multiple Stars Guide
How to resolve showcase binary and multiple star systems—Albireo, Mizar & Alcor, Epsilon Lyrae, Castor, and Sirius B—and test telescope Dawes limit.
Northern Summer Milky Way Observing Tour
Summer observing guide from the Summer Triangle (Vega, Altair, Deneb) and Hercules Keystone down the Milky Way rift to the Sagittarius Galactic Center.
Angular Size, Separation & Field of View
How angular diameter (degrees, arcminutes, arcseconds), spherical angular separation, and small-angle physical diameter relate to telescope field of view.
Trigonometric Parallax, Parsecs & Gaia DR3
How trigonometric parallax (d_pc = 1 / p_arcsec), the distance modulus equation, Hipparcos, and Gaia DR3 microarcsecond astrometry measure cosmic distances.
Scientific Sources & Dataset Provenance
- ESA Gaia Archive — Data Release 3 (DR3 (2022-06-13)): Gaia Collaboration, Vallenari, A., et al. 2023, A&A, 674, A1 (Gaia Data Release 3) — European Space Agency / Gaia DPAC
- Hipparcos New Reduction Catalog (2007 New Reduction): van Leeuwen, F. 2007, A&A, 474, 653 (Validation of the new Hipparcos reduction) — ESA / van Leeuwen (2007)
- SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg