This image of the Skull Nebula (NGC 246) in Cepheus includes 20.6 hours of S2/Ha/O3 imaging with a 235 mm SCT at f/7. Credit: Michael Borland (Flickr, CC BY 2.0)
Many constellations are famous for having a very special deep sky object within their boundaries, something so famous that when you read or hear the name of that constellation, you immediately think of it, like in an astronomical word association game . Orion? The Orion Nebula! Andromeda? The Andromeda Galaxy, of course! Lira? Easy: the Ring Nebula. And Perseus? It has to be the Double Cluster, right?
But not all constellations have that claim to fame. Many constellations are not home to a particularly striking or beautiful nebula, twinkling star cluster, or swirling galaxy, and so are often overlooked, like impatient tourists, by observers who pass through or past them on their way to more exciting destinations. These are the Shy constellations, the ones that hide in a corner of the living room during a star party, hidden behind a potted plant or next to the aquarium, talking to the dog while all the other constellations, safer and less socially awkward, dance together or hang out in the kitchen, laughing and joking while they eat all the pizza and appetizers.
But just because a constellation doesn’t have a celebrity feature doesn’t mean there’s nothing to see within it. Everything is fine The constellation has something within its borders worth tracking down, if you look hard enough, like these “five shy” deep-sky gems:
CETUS: The Skull Nebula, NGC 246
Also known as the Skull Nebula, NGC 246 is a planetary nebula approximately 1,600 light-years from Earth. It is also known by some observers as the Pac-Man Nebula due to its shape’s similarity to the greedy video game character it devours, but do not confuse NGC 246 with either other Pac-Man Nebula (NGC 281) or the much larger and brighter Rosette Nebula (NGC 2337), also known by some as “the Skull”.
With a magnitude around 11, NGC 246 is one of the faintest planetaries in the sky. Although it can be seen with smaller instruments from dark-sky sites, this nebula really needs a 6-inch or larger telescope to see properly: as a disc-shaped, lightly dappled haze with foreground stars scattered across of it.
ARIES: NGC 772, a beautiful galaxy
Let’s be honest, there isn’t much to see in Aries. It’s the celestial equivalent of a remote country town you pass through on your way to somewhere more interesting. But if you park and wander around, you’ll come across NGC 772, a cute 10th-magnitude spiral galaxy about 130 million light-years away.
With a diameter of about 250,000 light-years, NGC 772 is larger than our Milky Way. Long-exposure images show that the galaxy’s spiral arms are warped and distorted by nearby dwarf galaxies, but the arms are visually very faint and you will only see the bright core unless you use a large-aperture instrument.
CAMELOPARDALIS: IC 342, another beautiful galaxy
One of the shyer constellations, Giraffa Camelopardalis (hands up in case you forgot there’s a giraffe in the sky too!) is rather devoid of deep-sky objects, although many observers are drawn to the galaxy NGC 2403, which lies near the Giraffe’s mouth. But halfway up the Giraffe’s back is another deep-sky object that is shamefully overlooked and overlooked by observers.
IC 342 is a spiral galaxy of magnitude 8.4 relatively close to us, at a distance between 7 and 11 million light years. It can be seen with binoculars as a surprisingly large hazy patch, much like the much more famous M33, and telescopes easily spot its tightly coiled spiral arms. So why isn’t it better known? Maybe the same reason it’s called the Hidden Galaxy: because unfortunately IC 342 is behind a very dusty part of our Milky Way, so our view of it is pretty ruined. If it were elsewhere in the sky, IC 342 would be a lovely sight, easily visible to the naked eye.
LYNX: The Intergalactic Wanderer globular cluster, NGC 2419
While lynxes are beautiful creatures in real life, the constellation Lynx, sandwiched between Ursa Major and Gemini, is an unremarkable splash of faint stars. However, it contains something that is definitely worth looking for. The globular cluster stain.
Globular clusters famously orbit galaxies like moths flitting around streetlights, but astronomers once thought that NGC 2419 did not orbit the Milky Way and was instead some sort of rogue cluster. He was also nicknamed the Intergalactic Wanderer. We now know that it belongs to our galaxy, sometimes passing beyond the Magellanic Clouds during its 3 billion-year-long orbit.
SAGITTA: Globular cluster M71
If we could somehow actually turn on the “artwork” of the sky, as we can with a phone app or computer program, we would see an arrow resting on the paws of Vulpecula the fox. This is Sagitta, and its main purpose appears to be to guide observers towards the famous Dumbbell Nebula (M27), which lies just north of its sharp tip. But Sagitta contains an overlooked Messier object of its own: M71, a globular cluster 13,000 light-years away. M71 is a loose globular cluster, meaning its stars are less densely packed than those of better-known globular clusters. In fact, it probably looks more like M44 (the open Beehive cluster) than M13 (the famous Hercules globular cluster). A dark notch cut on the western side is very noticeable at high magnification.
These are just five objects that appear in the sky. There are many, many more. So, next time you go out on a clear night and point your telescope at the stars, don’t point it directly at your favorite objects, the cheeky ones that scream, “Look at me!” Ignore them. They won’t go anywhere. Give shy deep-sky objects a chance to tell you their stories for a change.
