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What is Epsilon Lyrae?

Commonly referred to as the “Double Double,” Epsilon Lyrae (pronounced EP-sill-on Lye Ree) is defined as a binary star consisting of binary stars. Confused? I’ll explain. 

You’ve probably read or heard about a double star system, which has two Suns shining in the sky. Some of these pairs just appear close together when seen from Earth. Other star systems are called “binary” because they are physically bound and orbit each other. 

Epsilon Lyrae appears as a single star, but upon close observation with the naked eye (or, easily, with binoculars), you can observe that it’s a binary star system. Two equally bright Suns orbit each other.

But that’s not what’s unusual. With through a telescope, it turns out that each of the two stars splits into two again! It’s a true physical double. What first appeared as a single star is actually a quadruple star system!

Epsilon Lyrae is also one of the easiest double stars to spot. Just focus on the brightest star above, Vega (pronounced VEE-guh), then look to the left. I’ll share viewing tips in a moment.

How Many Stars Make Up Epsilon Lyrae?

While it may appear as a single star, Epsilon Lyrae is a multiple-star system containing 5 stars: 

• Two binary star pairs that orbit each other (so, four stars)
• A fifth star, discovered much later, orbits one of those star pairs and is only detectable using specialized equipment

How Far Away is Epsilon Lyrae?

The star system lies about 162 away. These stars are very large (over twice the mass of our Sun) and very hot (about 7,900K). The first pair of stars is equally bright with similar magnitude (4.7 and 4.6), while the secondary pair of stars is dimmer.

How to View the Double Double

Night falls earlier and earlier in autumn. As the sky darkens, the very first stars appear (at nearly 7 PM). Epsilon Lyrae is located in the constellation of Lyra, close to the bright star Vega. 

1. Your first step is to locate Vega, the brightest star overhead. Its zenith position makes its identification easy. Along with Deneb and Altair, it’s known as the brightest star in the Summer Triangle. If you wait until full nighttime, which means 8 PM or so, Vega would no longer be perfectly overhead, though it’s still the brightest and highest star.  

We raved about why Vega deserves our attention, but today, our focus is on the little companion to its left: Epsilon Lyrae. 

2. Once you’ve found Vega, look more closely, and you’ll see several medium-faint stars near it. Four of these form a perfect parallelogram that supposedly represents a harp, along with a fifth star not part of the parallelogram. It’s this fifth star that holds our current interest.

3. This is the very nearest star to Vega, which is another way of locating it. To make the identification foolproof, fish out those old binoculars you’ve got lying in some drawer and point them at Vega. Its two nearest companion stars will join Vega in that same field of view. You’ll immediately see that the nearest of them is not a single point of light but two medium-faint stars close together: Epsilon Lyrae 1 and Epsilon Lyrae 2.

4. For the next step, you’ll definitely need a small telescope. Look again at Epsilon Lyrae 1 and 2. With telescopes with an aperture of six inches or above, you should see the two stars split into four! This is a telescopic four-star system, with two sets of suns whirling around each other while each duo orbits the other. For an appreciation of scale, each of the two-star pairs is separated by twice the diameter of our solar system.

As for the wide distance between the two pairs, it’s a fifth of a light-year and probably requires a million years to complete one orbital circuit around the other pair of stars.          

Celestial Eye Exam   

One other curiosity that makes the Double Double special is that it’s the very best test of one’s ability to resolve sharp detail.

This isn’t a method of checking if your eyesight is 20/20 (the acuity that is characterized as normal). Surprisingly, many young people, especially in their early teens, have much keener eyesight than that. They routinely see detail beyond 20/20, with sharpness measuring 20/15, 29/13, or even 20/10. So today’s venture is a simple one—to see if you (or your children) have better than 20/20 vision.

Can you discern that Epsilon Lyrae is not just one but two stars using unaided eyes (ie., no binoculars or telescopes)? My theory is that vision better than 20/20 can “split” the stars, meaning they can be seen as separate objects rather than as a single dot. 

When I lead an outdoor group of, say, 40 people, I’ll point out the star and ask if anyone can see it as two, not one. In a group that size, a few people, almost always among the youngsters aged 7 to 19, raise their hands and excitedly call out, “I see it!” while everyone else stares up morosely. Sometimes, to confirm their observation, I hold up both clenched fists toward the sky, assign letters to three possible angles of separation, and then ask whether the stars’ orientation was aligned as a, b, or c.

In all likelihood, most of us need binoculars to see this little star as being a double. It definitely requires a telescope to split once again. 

Just think: The four stars that make up the single dot lie around 162 light-years from us, in contrast to nearby Vega, which is just 25 light-years from Earth. That’s quite some splendid choreography parading overhead these nights at nightfall!