University Lowbrow Astronomers

Doug’s Deep Sky Challenge: Feeling Edgy Lately?

by Doug Scobel
Printed in Reflections: May, 2004.

Did the long, cold winter leave you feeling just a little bit on edge?  If so, then I have just the cure for you.  How about some springtime edge-on galaxies to brighten your spirits?  During spring, our nighttime sky faces the richest galaxy hunting grounds in our corner of the universe.  And a fair number of these galaxies present a nearly edge-on profile from our vantage point here on Earth, providing a unique view.  Now a couple of features of edge-on galaxies make them particularly pleasing to view in moderately sized amateur instruments.

The first thing you notice when viewing an edge-on galaxy is, well, it is edge-on (duh!).  The best examples look extremely long and narrow.  Usually you’ll see a bright central bulge.  Often you can see a dark, obscuring dust lane nearly bisecting the brighter outline.  Some of the best ones are so thin that they look like a glowing needle superimposed on the dark background sky.

The other thing that’s nice about edge-ons is that more often than not they exhibit a high surface brightness.  This is because their light is concentrated into a long, skinny area.  By comparison, a face-on spiral of the same brightness and the same diameter will look much dimmer because the light is spread out over a much larger area.  This high surface brightness makes the edge-ons good targets when observing under moderately light polluted skies, or when using smaller apertures.

When viewing these, as well as all galaxies, it is important to observe from as dark a sky as you can get to.  Even with the relatively high surface brightness of edge-ons, you need as much contrast between the galaxy and the sky background as you can get.  The best way to do this is by observing under a dark sky.  Also, don’t be afraid to crank up the magnification on these.  Their high surface brightness lets them withstand magnification well, and many will not reveal much structure and detail until you “kick it up a notch,” aperture permitting of course.

Enough talk - how about some observing?  Here are a few particularly notable springtime edge-on galaxies that I have observed (all using my 13” Dob) and consider to be “must-see”s.  I hope that you’ll find observing them enjoyable as well.

NGC 2683 is only magnitude 9.8, but it is fairly long and narrow and so has a high surface brightness making it easy to spot.  It appears to me to be nearly exactly edge-on, but I was unable to detect a dust lane.  Its core is noticeably brighter but not star-like.  Look for it in the constellation Lynx, about 6 degrees nearly due west of that constellation’s alpha star.

M82 (NGC 3034) is half of the famous, spectacular pair M81/M82 in Ursa Major that is a favorite target of amateur scopes.  While strictly speaking it is not an edge-on, it’s close enough and shows so much detail that I had to include it here.  It is classified as an irregular galaxy - astronomers are not quite sure what’s going on in its tortured-looking interior.  Visually, it looks very elongated, and very bright, like an edge-on spiral.  But instead of having a small, concentrated core area, much of the middle of the outline is very bright, with a lot of mottled bright and dark areas.  There’s also an obvious dark area that crosses the galaxy in the “short” direction just west of center.  This galaxy holds magnification well, so don’t be afraid to turn up the power on it.  It’s a beauty!

NGC 4026 is the smallest of the group I have described here, but it is worthy of being mentioned.  It is only magnitude 10.8, but like most edge-ons, it has a high surface brightness and so withstands high power well.  It has a bright, star-like nucleus, and is very needle-like at both ends.  I detected a hint of structure in the nucleus at high power.  Look for this little gem about three degrees south-southeast of Gamma Ursae Majoris, the bottom left star of the Big Dipper’s bowl.

NGC 4565 is perhaps the finest edge-on galaxy visible to observers in mid-northern latitudes.  In larger scopes it’s nothing short of spectacular!  This magnitude 9.6 beauty is nearly perfectly edge-on to our line of sight, and in a dark sky the needle-like extensions on each side seem to go on forever.  The narrow, dark dust lane extends nearly exactly down the middle from end to end.  This showpiece is located just two or three degrees east of the center of the cluster of stars making up “Bernice’s hair” in Coma Berenices.  I’m sure you’ll come back to it again and again.

M104 (NGC 4594), also known as the “Sombrero Galaxy,” is not quite edge-on, but it is close to being so.  This one will also become one of your favorites, if it hasn’t become one already.  It is easily found by sweeping due west about eleven degrees from Spica, the brightest star in Virgo.  What distinguishes it from most other galaxies listed here is that it has a very wide central bulge that can be seen extending quite far on either side of its very prominent dust lane.  It’s this visual appearance that gives it its common name.  At magnitude 8.0, it is also the brightest galaxy on this list.

NGC 4762 I like to call “Son of NGC 4565.”  It has a very similar appearance to its namesake, it’s just not as big and bright.  It has the same, needle-like appearance, with a central bulge and a bright nucleus.  There’s also a hint of a dust lane.  It’s in a pretty setting, too, being bordered to the south by an arc of three approximately 12th magnitude stars.  NGC 4762 is just over two degrees west and just a smidge north from Epsilon Virginis, making it easy to find.

NGC 5907 is another fine needle-like edge-on, with a bright nucleus.  It’s nearly as large as NGC 4565, but not quite as bright.  You can find this galaxy in Draco about three degrees south-southwest of Iota Draconis, softly glowing at magnitude 10.3.

If these edge-on galaxies have piqued your interest, then here’s a table with more information on these and some other good edge-ons that I have observed and recommend (you’ll have to wait until fall to see NGCs 891, 7332, and 7339, though):

        (visual)(arc minutes)(Mag/sq.
arc minute)
89102h22m42°22’Andromeda9.913.0 x 2.813.7
268308h52m33°24’Lynx9.88.4 x 2.412.9
303409h56m69°41’Ursa Major8.412.0 x 5.612.8
307910h02m55°39’Ursa Major10.98.0 x 1.513.4
311510h05m-07°43’Sextans8.98.1 x 2.812.1
343210h52m36°35’Leo Minor11.26.9 x 1.913.9
387711h46m47°28’Ursa Major11.05.1 x 1.112.7
402611h59m50°56’Ursa Major10.84.6 x 1.212.5
411112h07m43°03’Canes Venatici10.74.4 x 0.912.1
421612h16m13°07’Virgo10.07.8 x 1.612.6
424412h17m37°47’Canes Venatici10.417.0 x 2.214.2
425612h18m65°53’Draco11.94.1 x 0.813.0
456512h36m25°58’Coma Berenices9.614.0 x 1.812.9
459412h40m-11°38’Virgo8.07.1 x 4.411.6
463112h42m32°31’Canes Venatici9.215.5 x 3.313.3
476212h53m11°12’Virgo10.39.1 x 2.213.4
530813h47m60°57’Ursa Major11.42.6 x 0.411.3
586615h06m55°44’Draco9.96.6 x 3.213.1
590715h16m56°18’Draco10.311.5 x 1.713.4
733222h37m23°49’Pegasus11.13.7 x 1.012.4
733922h38m23°47’Pegasus12.22.6 x 0.812.9


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