Messier Guide: Early Winter

Most beginners probably start with telescopes that they received as Christmas presents. The timing is fortunate, because in many ways, early winter is the easiest time to learn deep-sky astronomy in the North Temperate Zone, especially from light-polluted locations.

The winter sky is full of bright stars and prominent constellations, including in particular Orion, which almost everyone recognizes. That makes it easy to orient oneself, and to locate deep-sky objects. In addition, most of the winter Messier objects are bright and easy to see, including most particularly M42, which many people consider to be the finest deep-sky object of all.

Unfortunately, there is a natural tendency to start with M1, which happens to be one of the hardest and least spectacular of all the winter Messier objects. Beginners who set out to observe all of the Messier objects starting with M1 often give up before they have even started.

Here are the objects that are at their highest in the evening sky during the early winter, from RA 3 to RA 6. I have also included M35, which barely fails to fit in this range of RA, but forms a natural group with M36/M37/M38.

 

Obj	S178	S70	U178	U70	Type	Con	RA	Dec	Mag	PBrt	SBrt	Size
M45	1A	1A	1A	1A	OCL	Tau	03:47.0	+24:07	1.2	—-	19.8	100
M79	2B	3B	3C	3C	GCL	Lep	05:24.5	-24:33	7.7	17.7	21.0	8.7
M38	2B	2B	2B	3C	OCL	Aur	05:28.4	+35:50	6.4	—-	21.6	21
M1	2B	3C	3C	4C	SNR	Tau	05:34.5	+22:01	8.4	—-	20.5	6×4
M42	1A	1A	1A	2A	C/N	Ori	05:35.4	-05:27	4.0	—-	20.5	40×35
M43	2B	2C	2C	3C	C/N	Ori	05:35.6	-05:16	9.0	—-	22.6	10
M36	2B	2B	2B	2B	OCL	Aur	05:36.1	+34:08	6.0	—-	20.0	12
M78	3B	3B	3B	4C	NEB	Ori	05:46.7	+00:03	8.0	—-	20.8	8×6
M37	1A	2B	2A	3B	OCL	Aur	05:52.4	+32:33	5.6	—-	21.1	24
M35	1A	2B	1A	3B	OCL	Gem	06:08.9	+24:20	5.1	—-	21.0	28

For a key to this table, see
Key to the Tables.

In addition to the objects described in this chapter, you may want to observe some of the late-autumn objects, from RA 0 to RA 3. Many of these have northerly declinations which make them readily visible from the North Temperate Zone well into the winter. In particular, M31 and its companions are always worth a look whenever possible.

If you stay up late enough, you can also easily observe the late-winter objects, from RA 6 to RA 9, and even the magnificent galaxy pair M81/M82 which is nearly at RA 10.

M45, the Pleiades

M45 is the first of the winter Messier objects to rise as seen from the North Temperate Zone, and it is a wonderful introduction to the Messier objects, especially for people with small telescopes and for urban and suburban observers. Even the smallest binoculars under the worst conditions reveal the signature seven stars forming a miniature dipper. At 25X or so, my 70mm refractor under urban skies shows all of the important stars of this cluster. I particularly love the arc of seven faint stars stretching from Alcyone (eta Tauri), the bright central star, down to the mag 5.4 star at the south edge of the cluster, and the lovely tight triangle of stars just west of Alcyone. Also worthy of mention is the lovely wide double star Burnham 536 in the center of the bowl, with two mag 8 components separated by 40″.

Extra aperture or darker skies do little to improve the appearance of the cluster; in fact, most large telescopes cannot deliver a wide enough field to frame the cluster well. M45 looks best in a field at least two degrees wide. Under dark skies, some people can see faint nebulosity around some of the stars of the Pleiades, but there is no hope of seeing this under urban or suburban skies.

M42 and M43, the Orion Nebula

M42, the Great Nebula in Orion, is by far the brightest nebulous object visible from most of the North Temperate Zone; its only serious rival is NGC 3372, the Eta Carina Nebula, which is never visible north of latitude 30N.

M42 is visible even in the smallest instruments under the worst conditions, but it is an object that responds very well to aperture. It is charming in my 70mm scope, gorgeous in my 178mm scope, breath-taking in my 318mm scope, and overwhelming in a 500mm scope or larger. It is also an object that responds well to high magnification, at least the bright central region.

M42 is a very large and complex object; you could study it for a lifetime and still find something new every time you looked at it. At the core of the nebula is the Trapezium, Theta 1 Orionis, a magnificent quadruple star, readily split at 25X or higher. With a medium-sized telescope (say, 150mm or larger) at highish power, you may be able to make out one or two more stars, titled E and F. E and F would be easy to see in small scopes if they were out on their own, but they tend to be overwhelmed by the glow from nearby A and C. Their visibility depends primarily on steady seeing; bright skies are only a minor obstacle.

The area right around the Trapezium is called the Huyghenian region, after the great Dutch astronomer Christiaan Huyghens who gave the first detailed description of it. This area is intensely bright, and is barely scathed by light pollution. It is quite small, only a tiny part of the whole nebula, and is best viewed at high magnifications, as much as 1X per mm of aperture or higher. Protruding far into the Huyghenian region is the dark nebula sometimes called the Fish Mouth. The line of three bright stars south of the Fish Mouth includes the components of the star Theta 2 Orionis.

M43 is actually part of M42, separated from the main nebula by a dark foreground cloud which is evident in long-exposure photographs. Visually, it appears as a vague, nearly circular cloud about 3′ in diameter around a brightish star 8′ NNE of the Trapezium. This is an attractive nebula through large instruments under dark skies, but it suffers badly from light pollution. It is fairly difficult in my 70mm refractor under urban skies, but gets easier with larger apertures and darker skies.

Stretching out from the Huyghenian region are two great arcs sometimes called the Bat Wings. The southern Bat Wing is particularly bright, being faintly visible in my 178mm scope under urban skies at around 60X, or in my 70mm scope under suburban skies at similar magnifications. Under very dark skies, the Bat Wings curve around and meet again half a degree S of the Trapezium, but there is no hope of seeing this from the city or suburbs.

I find narrow-band filters somewhat useful on the outer sections of M42, but I prefer the Huyghenian region unfiltered at high powers.

M78

M78 is bright for a diffuse nebula, but it is several orders of magnitude fainter and more difficult than M42. It is quite hard to see in urban skies, especially in smaller instruments, but under suburban skies it is visible although extremely hard in my 7×35 binoculars, and fairly obvious in my 70mm scope.

The nebula is slightly elliptical, roughly 3′ by 4′. Look for the central star or pair of stars, which give the nebula much of its charm. If you can see M78, you also have a good chance of seeing NGC 2071 20′ NNE of M78. NGC 2071 is smaller than M78, but otherwise very similar.

Unlike many faint objects, this one seems to show best at lowish powers, about 40X in my 70mm scope and 60X in my 178mm scope; the nebulosity tends to fade out at higher powers. But one of my notes says that at 120X in my 178mm scope, a new much smaller nebulosity appeared right around the two central stars, although the main nebulosity had disappeared.

M79

M79 is one of the lesser Messier globulars, quite hard to resolve in medium-sized scopes even under dark skies. However, it is bright and highly concentrated, and fairly easy to see even in small instruments despite the fact that it never rises high above the horizon at my latitude of 42N. It shows best at moderately high powers, around 50X in my 70mm scope or 80X in my 178mm scope. At lower powers, it may look like a fuzzy star.

Under suburban skies, I see a faint halo about 3′ across around a brilliant 1′ core. Under urban skies, only the bright core may be visible.

M1

M1 is very easy to locate off the moderately bright star Zeta Tauri, but it can be fairly hard to see under bright skies. It is fairly similar to M78, but perhaps a little bigger, brighter, and easier to see.

This object is rather attractive in large telescopes under dark skies, but is lackluster in small instruments and/or under significant light pollution. Its interest lies in the fact that it inspired Messier to compile his catalog, and in the nature of the object. It is the remnant of a supernova that was observed by Chinese astronomers in 1054, one of the few supernovas to have exploded in our own galaxy in historic times.

Like M78, M1 shows best at lowish powers, around 40X-50X both in my 70mm scope and in my 178mm scope. It requires averted vision through the small scope in the city, but is fairly easy to see in the larger scope in all conditions. It is a somewhat blocky patch of light, about 3′ by 5′, with fairly distinct edges. The SE quadrant is somewhat fainter than the rest of the object.

M36, M37, and M38

The three open clusters in Auriga are rather similar to each other in size and total brightness, yet each is quite different from the others.

M36 is the most prominent through small instruments; it is small and bright, consisting of half a dozen mag 9 stars, another half dozen mag 10 stars, and a modest coterie of fainter stars. Through my 7×35 binoculars, all of the stars merge to form a very small but fairly bright and prominent patch of light. The mag 9 stars stand out well in my 70mm scope at low and medium powers, and it is apparent that they are much more densely clustered than the mag 9 stars in the background. My 178mm scope brings out the faint background stars much more strongly. This tends to camouflage the bright stars of the cluster somewhat, making the cluster a little less prominent. M36 stands out best at fairly low power, but it show well at 100X or even higher. The cluster’s high surface brightness makes it fairly resistant to light pollution. Note the lovely double star Struve 737 slightly SE of the center, with mag 9.1 and 9.4 components separated by 11″. Struve 737 is slightly difficult to split in my 70mm scope under urban skies.

M37 has roughly the same total brightness as M36 but has twice the diameter, giving it much lower surface brightness and making it harder to see under heavy light pollution. Nonetheless, it stands out reasonably well in my 7×35 binoculars from the city, forming a fairly large, subtle, but attractive cloud of light.

Right in the center of M37 is a prominent mag 9.2 star, surrounded by a large number of fairly faint stars, very densely packed, and all within a fairly narrow range of brightness. In small scopes and at low magnifications, these stars tend to merge into an unresolved nebulosity, especially under heavy light pollution. At higher powers, numerous stars become intermittently visible with averted vision, a very lovely effect. In my 178mm scope, many stars are immediately evident even at low power, making the cluster very attractive and absolutely unmistakable. The cluster shows best at the highest power that frames it well, probably around 80X or 100X in an eyepiece with a 50-degree apparent field of view. At least 100 stars are visible in my 178mm scope at 100X under suburban skies.

M38 is as large as M37 but significantly fainter, giving it fairly low surface brightness and making it by far the hardest of the three clusters to detect under heavy light pollution. In my 7×35 binoculars from the city, it is a very vague smear of light, just slightly brighter than the background.

M38 contains about 20 stars from mag 9.9 to mag 10.9, more tightly clustered than similar stars in the background, but not dramatically so. Most of the brighter stars lie on two wavy lines crossing in the center, reminding me of the Greek letter chi. There is also a stubby projection from the center, making the cluster look a little like a starfish with one arm partially amputated. Under urban skies, most of the brighter stars are visible but not dramatic through my 70mm scope, making the cluster rather unconvincing. It improves under suburban skies. My 178mm scope shows all of the brighter stars immediately, and in darker skies or at higher powers, it also reveals another 20 or 30 fainter stars which help to flesh the cluster out. Because the cluster is rather vague, it needs a rather wide border to frame it well, best in a field of view around 1 degree.

In good skies, with a 150mm scope or larger, you may be able to pick out the small, faint cluster NGC 1907 just half a degree S of M38. It is not particularly interesting in its own right, but it forms a nice contrast with M38.

Although M38 is the hardest cluster to detect, it is very easy to locate, being almost exactly half way between iota and theta Aurigae. M36 and M37 symmetrically straddle a line connecting theta Aurigae and beta Tauri (El Nath), slightly closer to theta Aurigae. If the clusters cannot be found by the point-and-hope method, they are rather arduous star-hops from the nearest naked-eye stars.

The appearance of the three clusters reflects their underlying nature. M36 is a young, fairly sparse cluster, very much like M45, but about ten times more distant, making it appear ten times smaller and one hundred times fainter. The brightest stars are still on the main sequence, burning hydrogen, and showing white or blue.

M37 is much richer and much older. All of its very bright stars have already burned out, leaving the remainder fairly narrowly clustered in brightness. The brightest of the remaining stars are all red or yellow giants, near the end of their lives. The reddish color of the bright central star is particularly obvious in my 178mm scope.

Stars in a cluster interact much like the molecules in a fluid. The stars do not actually bounce off each other, but when two stars come close, their gravitational interaction has much the same effect. As in a fluid, the net effect is that the heaviest stars eventually settle to the bottom (the center of the cluster), while the lightest stars “evaporate”, or escape from the cluster. The heaviest stars are also the brightest, and the ones that reach red-giant stage the soonest; therefore, it is very common to find one or two bright red stars near the center of a mature cluster.

M38 is intermediate between M36 and M37; about half of the brightest stars are on the main sequence, shining blue or white, and the other half are red or yellow giants. M38 is dominated by a small number of stars considerably brighter than the rest, but not so few nor so bright as the bright stars of M36.

M35

M35 has something for everyone. Its brightest stars are even brighter than those of M36; a few are mag 8 or brighter, making them readily resolvable by my 7×35 binoculars under urban skies. But M35 also has plenty of stars in every brightness range below that, down to a cloud of mag 12 stars that rivals M37’s.

M35 is about half the distance of the clusters in Auriga (2000 light years as opposed to 4000), which accounts for the brightness of its stars and for its enormous apparent size. The brightest stars of M35 are split roughly evenly between the main sequence and the red giant branch; perhaps this is what M37 looked like before its brightest stars burned out.

M35 is faintly visible to the naked eye under the best suburban skies, and fairly easy under dark skies. It is also very easy to locate off the right-hand “foot” of Gemini, the star eta Geminorum, which is visible in all but the worst skies.

Nonetheless, M35 does not stand out as well as M36 in small instruments under heavy light pollution. Much of its brightness is contained in the half-dozen brightest stars, but those stars are spread out over a large area instead of forming a tight, distinctive pattern like that of M36. The fainter stars merge into a nebulous background that stands out well in dark skies, but its surface brightness is too low to be seen easily from the city.

In my 70mm scope, M35 shows best at around 60X. Under urban skies, this brings out just enough stars to make the cluster look like a cluster. M35 is spectacular in my 178mm scope even under the worst conditions, but it is a struggle to find a magnification low enough to frame the cluster well yet high enough to bring out its faint stars and resolve its intricate detail. 80X seems optimal with a standard Plossl eyepiece, but higher powers could be used if the eyepiece has a wider apparent field of view.

In good skies, you might take a look for nearby NGC 2158 about 20′ SW of M35’s edge. It shows quite easily even in small instruments under dark skies, but suffers badly from light pollution. Through a large telescope, NGC 2158 is one of the prettiest of all open clusters, even richer than M35. However, it is also much farther from us than M35, making it quite hard to resolve in modest telescopes