What Are Multiple Stars and Which Are the Best Ones?

Whenever you look up at the night sky you’re looking at hundreds - if not thousands - of stars. To the naked eye, they appear as single points of light, but the reality is that most stars are thought to be multiple star systems. In other words, that single point of light probably isn’t just one star, but several.

What Are the Different Types of Multiple Stars?

If you haven’t already, you’ll probably hear the terms “double star” and “multiple star” used a lot, and often interchangeably. For the sake of clarity, we’ll call a star system made up of two stars, or two stars close together a “double star”. If there are more than two stars present, we’ll call that a “multiple star”. Just to confuse matters a little, the phrases “double star” and “multiple star” are both often used generically.

You might also hear the term “optical double.” This is a pair of stars that simply appear within the same line of sight. In other words, they don’t form a true double star system and could, in actuality, be many light-years apart.

There are thousands of double and multiple stars that can be seen through telescopes, but here are a handful to get you started.

Showcase Stars for Spring

There are a number of double and multiple stars that are easily accessible to us during the spring, and if you’re familiar with the Big Dipper, you should have no problem locating them.

Let’s start with Mizar, the middle star in the handle of the dipper. Look carefully with just your eyes and you may see a much fainter, tiny star just beside it. This is Alcor, and in ancient times, spotting this star was considered a good test of your eyesight. Realistically, it shouldn’t present you with much trouble, even from suburban skies.

While it’s known that Mizar and Alcor aren’t far apart from one another and are moving in the same direction through space, it has yet to be conclusively proven that these two form a true double star system.

Turn any telescope toward the pair and you’ll see that Mizar itself has been split in two. The brighter star (the “primary”) appears about 50% brighter than its companion (the “secondary”). Besides Alcor, you’ll also see another star nearby, but this isn’t a part of the group. All of them will appear white or blue-white in color.

Image Credit: Greg Parker via AstronomyNow.com


Now, look at the star at the end of the dipper’s handle. This is Alkaid, and while it’s not double or multiple itself, there’s a star nearby that is. If the dipper appears upright, then look just a little way below Alkaid for a star that’s slightly fainter than Alkaid itself and about the same brightness as Megrez, the faintest star in the dipper.

This star is Cor Caroli, and it’s the brightest star in the tiny constellation of Canes Venatici, the Hunting Dogs. This is an easy split for almost any telescope at a low power of just 25x. The primary appears white and about two or three times brighter than the off-white secondary. Some observers describe the secondary as being slightly coppery or creamy in color - what do you see?

Unmissable Multiples for Summer

The star Vega is one of the closest stars to the Sun and, consequently, is one of the brightest in the entire night sky. It’s also the brightest star in the constellation Lyra, the Lyre, and serves as a very handy marker for one of the best multiple star systems you can observe with a telescope.

Within the same finderscope field of view as Vega is Epsilon Lyrae. Binoculars will show two white stars of equal brightness very close together, but a telescope of any size can reveal a lot more.

With a low-power eyepiece, you’ll easily be able to see the same two white stars that are visible with binoculars. Now you’ll need to increase the magnification to more than 100x. Since your scope probably didn’t come with an eyepiece that will magnify that much, you may want to buy an additional eyepiece for such high-powered work.

(Remember, magnification is calculated by dividing the focal length of the telescope by the focal length of the eyepiece. The smaller the focal length of the eyepiece, the higher the magnification.)

Image Credit: Viewfrom.earth

This is also where a Barlow lens comes in handy. A 2x or 3x Barlow will multiply the magnification of the eyepiece without losing any of the field of view. It’s, therefore, easier to observe with a Barlow and a long focal length eyepiece than with an equivalent eyepiece with a short focal length.

The two stars you can see at low power are about 160 light-years away and orbit one another, making this at least a double star system. However, each of the two stars seen here is also a double, making this a multiple-star system of at least four stars.

You may be able to split both stars into their two components at around 100x, but the chances are you’ll need something closer to 150x. All four stars will appear white and of almost equal brightness. As a result, Epsilon Lyrae has earned itself the nickname “the Double Double.”


If you’re looking for something a little easier, then look no further than the neighboring constellation of Cygnus, the Swan. Beta Cygni marks the head of the swan and is more commonly known as Albireo. This famous double is arguably the finest in the northern celestial hemisphere and can be easily split with any telescope at a low magnification of just 25x.

The primary has a strong golden light, while the fainter secondary appears sapphire-blue. A favorite with stargazers worldwide, it’s a showstopper at star parties and is guaranteed to wow anyone.

Autumnal Doubles in Andromeda and Aries

While many of the stars of fall can be faint, there’s one reasonably bright constellation that’s well-known and contains a number of interesting sights. Andromeda, the Princess, looks like two curved lines of stars stretching east from the Great Square of Pegasus, the Flying Horse.

Gamma Andromedae, also known as Almach, lies roughly 350 light-years away and is a multiple star system whose two brightest components mimic Albireo. A magnification of around 35x may be enough to split it, otherwise, you’ll need to increase it to around 50x. The primary star appears a pale white-gold while the fainter secondary is a light, ocean blue. Look carefully at the secondary, as it can sometimes appear to have a purple hue.

In neighboring Aries, the Ram, we find Gamma Arietis or Mesarthim. It’s one of the brighter stars in the constellation and is another easy double for almost any telescope. Again, you’ll only need a low magnification of about 35x to split the star, with two white stars of almost equal brightness being visible.

Image Credit: Wikisky

Bright Multiples for Winter Nights

Orion, the Hunter, dominates the winter skies and can be easily seen all season long. If you’re already familiar with the constellation, you should be able to find Meissa, a star with a violet-purple companion.

Meissa appears at the top of the constellation and forms a triangle with Betelgeuse and Bellatrix. A low power of around 25x will show a bright white star in a scattered field with a much fainter star nearby. Between the two is a third star, barely seen at this magnification, with all three stars being roughly equally spaced apart.

Turn your attention to the bright white star and increase the magnification to around 100x. The star should be split, with a close, fainter companion now visible on the opposite side from the other two stars. The color of this close companion can be a little hard to distinguish, but if you look carefully it appears to have a bluish-purple or violet tint.


You may also be familiar with the constellation Gemini, the Twins. If not, start at Bellatrix in Orion and draw a line through Betelgeuse. Keep going until you come to two nearly identical bright stars, fairly close together. These two stars, Castor and Pollux, each represent one of the twins.

Despite having the designation of Alpha Gemini, Castor is actually the slightly dimmer of the two, but unlike Pollux (a single star system) Castor is a multiple star comprising six suns in total.

Unfortunately, you won’t be able to see them all, but you should be able to split the star into its two largest components.

You’ll most likely need a magnification close to 100x, although magnifications somewhere between 50x and 100x might show the star as being elongated. You’ll see a pair of brilliant white stars, very close together, with the secondary being slightly fainter than the primary. These stars lie about 52 light-years away and take nearly 450 years to orbit one another.

Image Credit: Fred Espenak

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