IC342: An Obscured Spiral Galaxy, Hiding in Plain Sight

The nearly face-on spiral galaxy IC342 (Caldwell 5) in the constellation Cepheus. Image credit: Terry Hancock.

The nearly face-on spiral galaxy IC342 (Caldwell 5) in the constellation Camelopardalis. Image credit: Terry Hancock.

The galaxy IC342 ranks as one of the under-appreciated gems of the northern night sky. As you can see in the image above, this elegant nearby spiral galaxy in the far-northern constellation Camelopardalis (the Giraffe) is a photogenic target for experienced imagers. But it’s rather challenging to see visually in all but the darkest skies. It is, however, worth the effort to see this swirling assembly because it lies in an unusually beautiful field of foreground stars.

A nearly face-on spiral galaxy, IC342 (also known as Caldwell 5) lies at a distance of about 13 million light years, relatively close in cosmic terms. It’s part of the Coma-Sculptor Cloud of galaxies along with such objects as NGC 6946, NGC 147, and NGC 185 which also inhabit this part of the sky. IC342 is about 60,000 light years across or about 60% the diameter of our galaxy.

Unlike most galaxies, this spiral lies close to the flat plane of our own Milky Way. This means it lies in a rich field of foreground stars and this makes for excellent viewing or imaging. It also means the light from this galaxy is obscured by the dust in our galaxy by nearly three full magnitudes. If it weren’t for this dimming effect, IC342 would be one of the finest and brightest face-on spirals in the sky and easily visible to the unaided eye in dark sky. That would make it by far the most distant object you could see with the unaided eye.

The spiral nature of this galaxy wasn’t fully appreciated until 1934, a relatively late date, when the astronomers Edwin Hubble and Milton Humason imaged the galaxy with the 100-inch Hooker telescope at Mount Wilson in southern California. The galaxy isn’t a pure spiral. As you can see in the image above, it has a nascent bar near its nucleus so it may be evolving into a full-fledged barred spiral galaxy.

The location of the spiral galaxy IC342 (Caldwell 5) in the constellation Camelopardalis.

The location of the spiral galaxy IC342 (Caldwell 5) in the constellation Camelopardalis.

Look for IC342 for yourself about 3º south of the 4th-magnitude star γ (gamma) Cephei (see map). The galaxy has a total brightness of 8th-magnitude, but this light is spread over a diameter of about 15′, about half the size of the full Moon. So it has very low surface brightness and it’s all but invisible in light-polluted skies.

In good dark sky on a clear night, you can spot this distant stellar congregation as a dim smudge with any pair of binoculars. Turn a telescope towards it and insert your lowest-power eyepiece to keep the image bright and nicely framed. A good 6-inch or 8-inch reflector works well at 50x or less. Now use your best observing skills to look for the three very faint and clumpy spiral arms. They are there, but it takes averted vision and a lot of patience to see them.

 

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