The months move along quickly and we are ready for our next edition of the Monthly
DSO Challenge. For the northern February run, we head to Hydra for a fine open cluster; into Lynx for a beautiful and haunting nearly edge on galaxy; then wrap up in Gemini for a curious dual-lobed planetary nebula that also carries a dual identifier within the New General Catalogue (
NGC). In the southern section this month we visit Puppis for a very interesting duo, one imposed in front of the other. Then we finish in the deep southern constellation Volans, the flying fish, with a very intriguing barred spiral galaxy that likewise has two designations within the
NGC.
I hope you find this month’s selections fun and interesting to observe, image and/or sketch. There are easy ones and others that are a bit more challenging. But of course they only represent a tiny portion of what is up there on the canvas of the night sky. So I encourage you to get out there and enjoy what the universe puts on display each and every night – weather permitting of course.
Northern Celestial Hemisphere
Messier 48 / NGC 2548 (Hydra, open cluster, mag=5.8, size=30.0’, class=I2m):
I will ask your indulgence here because M48 actually lies nearly 6° south of the celestial equator. However, it is a very common object for us northerners and I wanted to give you all a nice bright open cluster that I had not featured before to start off this month’s journey. As the celestial water serpent begins to rear its head in the southeast, it is a harbinger of the spring to come for many of us northerners. But we still must endure our cold weather and spring seems a far off hope. The prominent serpent head is formed by Zeta (mag 3.1, Epsilon (mag 3.4), Delta (mag 4.2), Sigma (mag 4.4) and Eta Hydrae (mag 4.3). About 11° southwest of this
asterism, hugging the border with Monoceros, one will easily find this bright open cluster. In dark areas it may be glimpsed with the naked eye as a small fuzzy glow, and is certainly easy in optical finders and small
aperture scopes. It is a bit loose and straggling across its field, but easily apparent in the sky, dominated by a narrow wedge of 8th and 9th mag stars flowing southeast-northwest. There are numerous dimmer stars dotting the field. Though not a visually stunning object, it is not a disappointment either.
Discovered by Charles
Messier in 1771, he described it as a "cluster of very faint stars, without nebulosity; this cluster is a short distance from the three stars that form the beginning of the Unicorn's tail." However, he poorly calculated its position and it remained a lost object of his for nearly two centuries. It was independently discovered by both Johannes Bode and Caroline Herschel, the latter of whom was erroneously given credit in the
NGC by Dreyer. Eventually the snafu was worked out and
Messier is given due credit for its discovery.
NGC 2683 (Lynx, spiral galaxy, mag=9.8, size=9.3’x2.1’, SBr=12.8):
This bright spiral galaxy was discovered by William Herschel in 1788, who called it “a beautiful object” and noted its elongated shape and that its brightness was cutoff suddenly along its side, which is indicative of the presence of heavy dust obscuration along the northwestern edge of its core area. Its eerie appearance in deep images garnered it the nickname of the “UFO Galaxy.” Tilted southwest to northeast, it appears as an elongated glow that can appear mottled and unevenly illuminated due to the dustiness of the arms. Its southwestern extension is brighter and more prominent than is the northeastern portion. Because of the dustiness northwest of the core, this lends it an uneven appearance along its major axis. From dark locations it can be very bright and particularly in medium to large
aperture, reveal some curious detail. Even in a typical suburban area, it is not difficult with medium sized apertures and one can also begin to glimpse hints of its interesting structure. Give it a look and see just how much of its unusual appearance your eye can pick up.
NGC 2371/72 (Gemini, planetary nebula, mag=11.2, size=1.2’x0.9’, SBr=11.0):
This interesting bipolar (two-lobed) planetary is affectionately called the “Double Bubble” and sometimes the “Peanut Nebula.:” Discovered by William Herschel in 1785, he saw it as two distinct objects in very close proximity. That is the reason it was later put into the
NGC as two objects, though in fact, it is a single object. In medium to large apertures one can see two knots of brightness (the two lobes) oriented southwest-northeast inside of a dim halo. With larger
aperture one may catch a glimpse of the mag 14.9 central star more or less equally placed between the two lobes. If you have an O-III line filter, you can get a better visual presentation, but even a narrow-band nebula filter will be beneficial. The Double Bubble is indeed a very curious object and is a good challenge of your observing skills, particularly in areas of increased sky glow.
Southern Celestial Hemisphere
Messier 46 / NGC 2437 (Puppis, open cluster, mag=6.1, size=20.0, class=III2m:
This open cluster is easily found using binoculars, presenting an obvious fuzzy concentration of light. In a telescope its true nature becomes readily apparent as a dense round evenly clustering of dimmer stellar points. Though the cluster contains just over a dozen stars of 10th magnitude, the bulk of its stars are in the 11th to 13th magnitude range. While overall bright, the multitude of dimmer stars gives it a smooth and evenly illuminated look. I find it a rich conglomeration of stars, but not as in your face as some other clusters, such as nearby M47 to its WNW (which you should also check out). Discovered in 1771 by Charles
Messier, it was also observed by Caroline, William and John Herschel, with William describing it as "a beautiful, very rich, compressed cluster of stars of various magnitudes." This cluster also presents us with an added bonus. For that, see the next object, and enjoy both.
NGC 2438 (Puppis, planetary nebula, mag=10.8, size=1.3’, SBr=11.1):
Seemingly swimming among the stars in the northern portion of
Messier 46, keep an eye out for this nice planetary nebula. Discovered in 1786 by William Herschel he commented that it had no connection with the cluster since the cluster itself was free of nebulosity. While it is easy to assume that the planetary is within the cluster, it is known to be a foreground object. In smaller apertures it may not always be so easy to discern against the dizzying backdrop of dim cluster stars. Using either a narrow-band nebula filter or O-III line filter will help out with that task. Once you have affixed its position within the cluster field, try removing the filter and you should be able to see it without the filter. In larger apertures it is quite apparent against the cluster’s stars and can present hints of annular structure. One may notice a 13th magnitude star just northwest of its center, but this is not the true central star, which is a white dwarf of magnitude 17.5. I have always found it intriguing when two different types of
DSOs are in such close proximity and I hope you enjoy this dynamic duo.
NGC 2442/43 (Volans, barred spiral galaxy, mag=10.4, size=5.5’x4.9’, SBr=13.8):
We now swing deep into the southern sky for this very interesting and beautiful barred spiral galaxy. Located within Volans the flying fish, it was discovered by John Herschel in 1834 who noted “A double nebula; very large.” The double nebula he described was because his initial impression was of the southwestern and northeastern sections of the galaxy separated by a stellar presence (the core). During subsequent observations Herschel did determine this was one larger “nebula” rather than two smaller ones. However, Dreyer erroneously kept the two distinct
NGC numbers in his catalogue.
Informally known as the “meat-hook galaxy” due to its hooked appearance in deep images, it can display a bright core set within a thick diaphanous bar shaped body. The hooked arms are more difficult typically, but can be glimpsed with larger
aperture. Images of this curious object are entrancing and tickle the imagination with its “S” shaped envelope.
And that wraps it up for another month. I hope you get as many opportunities to commune with the night sky as possible. It can be a time of peace, a time of introspective thought. Engaging the night sky can be ethereal and a source of visceral emotions, as we engage something so immense and unfathomable.