Astronomy for Beginners, Part 2 - The Galaxy, or Hunting DSOs

Next time you're outside on a clear night, stand a moment and look up.  That's a lot of stars, right?

Photo by Dambldore via Wikimedia Commons

EVERYTHING YOU SEE that's not a distant galaxy is actually inside our own galaxy, the Milky Way (with a few exceptions).  That includes all the stars, star clusters, and nebulae you can find with a telescope.  Nebulae, clusters, and other galaxies are collectively referred to as Deep-Sky Objects or DSOs.

So what should a beginner look at?



There are many stars that will become more interesting once you have a pair of binoculars or a telescope.  For example, some stars prove to be doubles, such as Albireo, the head of Cygnus the Swan (photo by Jim Spinner):

Some stars have a beautiful color, such as Herschel's Garnet Star (Mu Cephei) in the constellation Cepheus.  Mu Cephei is thought to be the largest star visible to the naked eye.  Because it is at the end of its life, it has swollen and turned a reddish-orange color:


Other stars are variable, meaning that they change their brightness on a schedule.  For example, Algol, which represents Medusa's eye in the constellation Perseus, is an eclipsing binary.  Every 2.86 days, the dimmer star of the pair blocks the brighter star.  Ancient peoples called Algol the Demon Star, perhaps because they thought evil spirits were stealing its light!


Some stars form interesting patterns, or asterisms.  Try using your binoculars to find Brocchi's Clusters, aka the Coathanger.  You can find it by tracing an imaginary line past Aquila the Eagle's head, past the fletching of Sagitta the Arrow.  Hint: The coathanger is upside-down in this photo:

Before we embark upon our deep-sky adventure, here is a tip for viewing DSOs: Try gazing just to the right or left of the object and let your peripheral vision take over.  The center of human vision is dominated by cones, which see color but don't work well in the dark.  What you want to use are your rods, which control your night vision.  Unfortunately, this means that the beautiful colors you see in astronomical photographs simply aren't visible to the human eye.  Don’t be surprised when all of the DSOs you view are in shades of gray.  They're called faint fuzzies for a reason!



Open clusters are groups of a few thousand stars, siblings born from the same molecular cloud at about the same time.  Because they are loosely bound by gravity, they can lose members as they travel through the Milky Way.  The most famous open cluster is the Pleiades or Seven Sisters (or if you like Japanese cars, Subaru!)  It's visible as a small kite shape above the constellation Taurus the Bull.  A good test of your vision is to count how many of the stars you can see with the naked eye.  Hint: There are more than seven of them!  Check out the Pleiades with binoculars for the best experience.  (Photo by Rawastrodata.)


My favorite open cluster is the Double Cluster in Perseus.  In a dark sky, you can see this pair with the naked eye, but they're best in a telescope.  (Photo by ItFrightensMe.)

To find them, start at Cassiopeia and draw an imaginary line from Gamma to Delta.  Then continue two more "steps"--a double jump for a Double Cluster.  (Chart by


Globular clusters (fondly referred to as globs) are exactly what they sound like--round globs of hundreds of thousands of stars, tightly bound together by gravity.  The best of these (and one of the best sights in the sky) is the aptly-named Great Globular Cluster in Hercules.  You'll need binoculars to spot it, but try to see it in a telescope if you can!  Here's a photo from the Hubble:

"My God, it's full of stars!"

A dimmer glob, easier to see this time of year, is Messier 15, located just past the tip of Pegasus's nose.  Its stars are 12 billion years old, locked together as they orbit a black hole.  (Photo by HeWhoLooks).



Planetary nebulae are the remains of old stars that went nova, shooting off their outer layers of gases into interesting shapes.  Fun fact: Someday our sun will explode into a planetary nebula!  Will it become a dumbbell?  A ring?  We'll never know because we'll all be dead long before that!  (Photo by Charlemagne920.)

M37, the Dumbbell Nebula

My favorite planetary is the Ring Nebula in Lyra.  It looks like a tiny space doughnut!  But don't waste your time hunting for it with binoculars.  You need a telescope for this one.  (Photo by RawAstroData.)


Diffuse nebulae are giant clouds of gas and dust.  Often they are stellar nurseries, where new stars are born.  There are a few kinds of diffuse nebulae.  Emission nebulae glow brightly due to ionized gases.  Reflection nebulae reflect the light of stars in their dust.  Dark nebulae are so dense that they block the light from everything behind them, making them appear like black streaks in space.


The most famous diffuse nebula is Messier 42, the Orion Nebula.  This bright emission nebula is faintly visible to the naked eye, but try it with binoculars or a telescope and prepare for your breath to be taken away!  Unlike most DSOs, this one's bright enough for the human eye to make out a bit of color.  (Photo by Brian Goff.)

I think it looks like an eagle in flight.  What shape do you see?



In addition to all the DSOs you can see within the Milky Way, you can also view other galaxies (and in some cases, you can see star clusters belonging to those galaxies).  The easiest galaxy to see is our neighbor, Andromeda.  Andromeda is so huge that if we didn't have annoying little things like sunlight and atmosphere getting in the way, it would appear bigger than the full moon.  In a dark sky, you can spot the Andromeda Galaxy with the naked eye.  Even with light pollution, you should be able to see its bright galactic core with a pair of binoculars.  (Photo by Adam Evans.)

Fun fact, Andromeda and the Milky Way are on a collision course that will fling our Sun out of its orbit and send it on an eternal voyage into the cold emptiness of space!  Fortunately we'll all be dead before then.

The Milky Way and Andromeda are both part of the Local Group, a collection of more than fifty nearby galaxies.  Along with Triangulum, they are the three biggest members, so large that smaller galaxies can become gravitationally bound to them.  Our galaxy has many satellite galaxies, but the most famous of them are the Large and Small Magellanic Clouds.  Unfortunately for us, you have to travel to the Southern Hemisphere to see them.  (Photo by J. Colisimo.)

BRB, I'm booking a flight to Chile!

Check out these other nature articles:

Astronomy for Beginners, Part 1 (The Solar System)

Owls of Indiana

What's in a vernal pool? (Fun With Plankton)

Birding at the library?!

What's Blooming Now? Hayswood Nature Reserve

What's Blooming Now? Woodland Edition

Frogs and Toads of Harrison County

Spider Identification

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