Epsilon Lyrae 1 and 2

 

Epsilon Lyrae the multiple star system.
Data Credit: PIRATE robotic telescope (Clear and BVR filters).
telescope.org, Open Observatories, Open University.
Image Credit: Kurt Thrust.

"In a dull moment at the Observatory, the JPO Team fell into conversation about the famous double double star, Epsilon 1 and 2, in the constellation Lyra.No one was sure as to whether they had seen the gravitationally bound stellar system through a telescope eyepiece which resolved the target into four stars. Kurt thought that he had once achieved this with the JPO's 127mm refractor at high magnification but if he had it was so long ago that he could not be sure. We looked through the JPO's extensive archive of images but could find none relating to Epsilon Lyrae. As an afterthought, Kurt programmed the PIRATE telescope to capture an image. Clearly the large aperture PIRATE robotic telescope on Mount Teide had sufficient aperture but insufficient magnification to split the star system into four separate stars". - Joel Cairo CEO of the Jodrell Plank Observatory.

" Joel asked me to provide the following overview for the Epsilon Lyrae star system:

Epsilon Lyrae: The Double Double

Situated near the bright star Vega in the constellation Lyra, Epsilon Lyrae is among the best-known multiple star systems in the northern sky. To the unaided eye, it appears as a single faint star of about fourth magnitude, but through even a modest pair of binoculars it is revealed as a close double — two nearly equal stars separated by about 208 arcseconds. These two components are traditionally labeled ε¹ Lyrae (the western pair) and ε² Lyrae (the eastern pair).

What makes Epsilon Lyrae remarkable is that each of these stars is itself a tight binary. Thus, the system has earned the nickname the Double Double. Through a telescope of about 100 mm (4 inches) aperture under steady seeing, each component can be resolved into two stars. The separations are small:

ε¹ Lyrae (STF 2382) splits into a pair of magnitude 5.1 and 6.1 stars, separated by only 2.6 arcseconds.

ε² Lyrae (STF 2383) splits into a slightly wider pair of magnitude 5.4 and 5.5 stars, with a separation of 2.3 arcseconds.

Both pairs orbit each other over timescales of centuries, and the wider ε¹–ε² pairing is gravitationally bound, though the orbital period is measured in tens of thousands of years. The geometry of the system gives observers a striking contrast: ε¹’s stars are aligned roughly north-south, while ε²’s pair is oriented nearly east-west. This nearly orthogonal arrangement makes the system especially pleasing to amateur astronomers who succeed in splitting all four stars.

From a physical standpoint, the Epsilon Lyrae stars are main-sequence A-type stars, somewhat hotter and more massive than the Sun, shining white due to their surface temperatures of around 8,000–9,000 K. They lie at a distance of about 162 light-years (49.6 parsecs).

In observational astronomy, Epsilon Lyrae is often used as a test of both atmospheric seeing and optical resolution. Smaller telescopes may split the wide pair (ε¹ vs ε²), but only instruments of sufficient aperture and magnification under steady skies will reveal the close binaries that make the system a true Double Double". - Professor G.P.T Chat visiting astrophysicist at the Jodrell Plank Observatory.