Beta (β) Lyrae, Zeta (ζ) Lyrae, and even Eta (η) Lyrae!

One of the things that has always amazed me about the constellation Lyra is all but one of the stars that make up its outline are multiple systems of stars.

The Lyre of Lyra. Stellarium screen image with labels added, click on the image for a larger view.

You can start in the north with Vega (a triple with magnitudes of 0.0, 9.5, 9.5, and separations of 78″ and 118″) and from there move northeast to Epsilon (ε),  then south to the parallelogram where you come to Zeta (ζ) in the northwest corner.  To the east of it is Delta (δ) and the beautiful open cluster Steph 1 —  and over in the southwest corner you find Beta (β), also known as Sheliak.  Gamma (γ), in the lower southeast corner is the exception, but if you look at in a scope, you’ll find a difficult double just to the west of it, β648 (magnitudes of 5.4 and 7.5,  separated by 0.8″).  Tonight, with the moon close to full, we’ll stay on the west side of the Lyre and save the very beautiful Delta (δ) and its surroundings for a later time.

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Beta (β) Lyrae (Sheliak)  (Σ I 39)    HIP: 92420   SAO: 67451
RA: 18h 50.1m   Dec: +33°  22′
Mag:  AB – 3.6, 6.7     AE: 3.6, 10.1   AF: 3.6, 10.6
Sep:  AB –  48.6″         AE:  66.8″         AF: 86.3″
PA:    AB – 148°  (WDS 2011)       AE: 318°       AF:  19°   (AE & AF  WDS 2009)
Distance: 881.5 Light Years
Spectral Classification for A & B: B7, A8

The two main components of Beta (β), “A” and “B”, are a beautiful sight in a 60mm scope at 48x.  The primary is a bright white, which stands out well against a background of much fainter stars. The 6.7 magnitude companion can best be described as gray — well, gray with a tinge of white.  Now I never thought I would see that color in a star, and I checked it again several times before I was convinced, but gray it was.   However, in my 152mm refractor at 68x, the primary had picked up a yellow tinge and the secondary was now a whole lot more white.  Sheliak, by the way, is Arabic and refers in some way to the lyre, or harp.

In the larger scope, I noticed a pair of fainter stars just to the north of the primary which looked suspiciously like they might be part of a system linked to A and B.  The Haas book says nothing about a multi-star system, so I checked the Night Sky Observers’ Guide and found there are actually six stars in this system.  The “C” and “D” components are thirteenth magnitude, however, so unless you have about fifteen inches of aperture, you’re not going to see them in the glare of the much brighter primary and secondary.

One of the great advantages in using a larger scope along with a 60mm (I have the 60/800 mounted on a 152mm f/8 refractor) is that you notice things in the larger scope that you miss in the smaller one — especially when the moon is about 98% full, as it was on this night.  Going back to the 60mm refractor, I looked again — much more carefully this time — and first the “E” component popped out of the darkness, and then the “F.”  Switching from 48x to 76x, they were much easier to see.  If the moon hadn’t been a factor, I probably would have noticed them sooner, or if I had known they were there to begin with, I could have picked them out.

Anyway, it’s not every night you come across a system with six stars in it, four of which are visible in a 60mm refractor.  And as an added bonus, if you sit patiently for a couple of minutes, the Ring Nebula (M57) will come into view from the southeast — or if you’re impatient, just move the scope a bit in that direction to see it.  On an almost full moon night, it was a ghostly presence in the 60mm scope.

Zeta (ζ) Lyrae  (Σ I 38)     HIP: 91971    SAO: 67324
RA: 18h 44.8m   Dec: +37°36′
Magnitudes (AD) : 4.3, 5.6
Separation (AD):   43.8″
Position Angle (AD):  150°   WDS (2011)
Distance: 153.6 Light Years
Spectral Classification: A, F0

With the moon gleaming off the side of both scopes, I shifted north to Zeta (ζ).  Looking in the eyepiece of the 60mm scope, I thought I was back at Beta (β).  The position angle of the two stars is identical to the two brighter components of Beta (β), and the separation is within two arc seconds of it as well!  Missing were the two fainter companions of Beta (β), but if I had a larger scope, or the moon wasn’t so bright, I might have been able to see  three more faint components: a 12.5 magnitude star 26 arcseconds away, a 10.0 star at 46 arc seconds, and an 11.5 companion at 62 arcs econds.  (I’ll be back!)  And — we’re not done yet — there are an additional two spectroscopic components, so we have SEVEN stars in this system.

In the 60mm at 48x, the primary was yellow and the secondary was white.  In the six inch at 68x, both stars appeared to have almost identical yellow hues to them.  Haas includes some green in her description of both, but if it was there, it couldn’t be seen in the moonlight.  At any rate, in both of the scopes, the two bright components stood out well against a field of much fainter stars.

Eta (η) Lyrae (Aladfar)    (Σ 2487)      HIP: 94481     SAO: 68010
RA: 19h 13.8m   Dec: +39° 09′
Magnitudes: 4.4, 8.6
Separation:   28.5″
Position Angle:   79°   (WDS 2010)
Distance: 1042 Light Years
Spectral Classification: B2.5, A0

And now, just because it’s located way off to the east by itself (look about 6.5 degrees east of Vega) – and it rhymes well with Beta (β) and Zeta (ζ) – we’ll wander over to Eta (η).  After the much brighter secondaries of the two previous stars, I had to look closely to see the 8.6 magnitude secondary here.  In the six inch refractor, the primary was yellow-white and the secondary blue.  In the 60mm at 48x, the primary lost it’s yellow tinge and the secondary was too faint to call anything other than bluish.

Like Beta (β), Eta (η) has a name associated with it.  Aladfar refers to an eagle’s talons, which obviously has nothing to do with a lyre or harp, unless the eagle had some musical ability.  The primary is 6500 times more luminous than our sun and is approaching a transition toward the red giant stage.  The secondary is not actually gravitationally attached to Eta (η), so we’re looking at an optical double in this case.  There is the possibility, however, that a spectroscopic companion exists, and is as close as .6 astronomical units to Eta (η).

By now the bright moonlight was finding it’s way over my shoulder and into the eyepiece, so not one to ignore a hint, I got up from my crouched position at the bottom of the refractors, and swung them around to take a quick look at the moon.  Time for a break!

These observations were made in the early hours of June 27th, 2010.

Much of the information on these stars came from James Kaler’s excellent web site, which can be found here.