Big, Bright & Beautiful in December
By Max Gardner AM
As the days lengthen, the twilight lingers and the commitments of Christmas and school holidays crowd in, it's easy to put off observing. There are some wonderful sights awaiting along the meridian at 10pm this month. Try to make the time to get out there and see the majestic objects that summer nights have to offer. At least you can save on sunscreen! Grab the charts while the moon is absent and lets get going.
Starting as ever in the northern sky, we have two bright naked eye clusters to explore. Right on the meridian in the constellation of Taurus lies the beautiful naked eye group of closely placed stars known as the Pleiades or M45.
If you want to start an argument any summer weekend at Crago Observatory or Ilford, make a statement about how many stars can be seen without optical aid in this cluster. Seven? Ten? Five? It is a very personal thing, but also depends on sky conditions and location, etc. Binoculars increase the number of stars greatly and show the beautiful colors in the brightest stars. A telescope fitted with a low powered eyepiece will show greater detail, perhaps even hints of nebulosity, while larger apertures will show stunning detail in the distinct areas of bluish, wispy nebulosity surrounding the two brightest stars in the cluster, Merope and Maia, both 4th magnitude. Some observers have difficulty seeing this rather delicate nebulosity; it requires good sky conditions and a dry (i.e. dew-free) night. I find higher power works better. Persevere - it's worth it.
A little to the east is the much bigger and looser "cluster", the Hyades, or the head of the bull with its distinct triangular shape containing the red first magnitude star Aldebaran. This group is best seen in binoculars or the scope finder which will show the colors of the component stars. There is no nebulosity. Nor is there any formal catalogue classification of this group as a cluster.
Now let us move due south of the Hyades, across the border of Taurus into the galaxy-rich domain of Eridanus. Four degrees northwest of the 3rd magnitude star Gamma Eridani lies the 10th magnitude planetary nebula NGC 1535. While found by most small scopes, this object needs some aperture to see well. My observing notes say "It shows a large disk, bright over the whole face with a hazy perimeter. Faint spokes can be seen over the outer third of the disk. There is no central star."
Moving a back a little to the north and west, over the border into the constellation of Cetus, just under one degree south east of the 4th magnitude star Delta Ceti, lies the 9th magnitude spiral galaxy M77. A telescopic object, it shows some interesting features to larger apertures as my notes record: "A spiral galaxy that initially looks elliptical. It has a very bright round (Seyfert) core, a bright inner oval bulge with faint 'spokes', then a large and fainter outer halo or arms." Seyfert galaxies have very optically bright cores, indicating dramatic activity is taking place in the core, often also detected at radio wavelengths.
Further south and west, back into the wandery constellation Eridanis, about two and a half degrees north of the 4th magnitude star Tau 4 Eridani is the spiral galaxy NGC 1300. While not very bright at magnitude 10.4, it has interesting features for larger apertures. I noted: "A large, low brightness spiral. It has a small oval barred core, quite bright. There are long, faint, curved arms with mottling."
A few degrees south and east lies NGC 1395, a 9th magnitude elliptical galaxy that is classified as "peculiar". The reason for this is that elliptical galaxies normally look pretty bland - they are reasonably round with a central core and a smooth appearance. There is not much to excite your eye. In this case my notes record: "A large elliptical galaxy it has a bright oval core, large, regular halo and a hint of an outer ring or structure!." Clearly an outer ring structure on an elliptical galaxy takes some explaining. Unfortunately the ring needs a lot of aperture to see - but it is there if you have a scope with enough grunt.
Moving due south by three and a third degrees, just over the border into the constellation of Fornax we find another interesting spiral galaxy, NGC 1398. It displays a very large oval bright core, an extended round halo and a faint outer arm structure not dissimilar to NGC 1395. Less than half a degree away to the northwest is the unusually shaped planetary nebula NGC 1360. Shining at magnitude 9.4, it appears oval in smaller scopes, but shows an hourglass shape (known as "bipolar") with much internal structure to larger apertures.
Moving south and further east back into Eridanus and to a point one and a half degrees north-west of the magnitude 3.6 star Upsilon Eridani, we find the rather spectacular elongated galaxy NGC 1532. At 10th magnitude it is reasonably bright and my notes record: "A great elongated galaxy with a bright barred core and prominent bulge. The disk is very extended and slim, with much structure, knotting and H-11 emission regions. There is a prominent dust lane crossing the disk just southwest of the core. It makes a fine pair with NGC 1531, which is just west of the centre of 1532."
Now we move west across into Fornax and a little further south we encounter the Fornax galaxy cluster, another rich region of the sky. It is literally teaming with galaxies that most scopes can easily see. The centerpiece is NGC 1365, the famous "S"-shaped spiral galaxy that is often used as a cover shot on prestigious magazines. Smaller scopes will see the bright central bar and a hint of the massive arms, but these really need aperture to reveal detail. My observing notes say: "The famous 'S' shape spiral. The bar is bright and high power shows a star and a knot to the northwest of the bar. Both spiral arms are extensive and of low brightness but are well seen and have copious knots and structure. A great object!" Just over one degree to the north-west is the large 9th magnitude elliptical galaxy NGC 1399 which has the usual boring bright core and round halo, but also has a tiny 14th magnitude companion, NGC 1395 which appears to be almost in contact on the west side. There are many smaller galaxies in the vicinity, making a sweep around the area most rewarding. Also try the 9th magnitude galaxy NGC 1316, just three and a half degrees to the southwest. My notes of this object say: "A huge bright barred spiral with a massive, very bright core and extensive halo. NGC 1317 is adjacent."
Seven degrees south, back in the wandery constellation of Eridanus, brings us to the 9th magnitude galaxy NGC 1291. When I first came across it, I thought I was looking at a globular cluster, as my notes show: "This looks like a cross between an elliptical galaxy and a globular cluster. It has a very bright, dense, round core with a bright inner mottled halo. There is an extensive fainter outer halo, more obvious on the south-west side."
Fourteen degrees due south in the constellation Horlogium is the pretty globular cluster NGC 1261, which lies in an area of sky with few naked eye stars to star hop from. I recorded the following note: "It is well resolved into a myriad of tiny stars across the whole face. There is a well condensed core and a moderately wide edge, flattened to the north-east and extended to the south-west." Almost nine degrees due east, in the constellation Dorado, is the bright galaxy pair NGC 1549 and NGC 1553. Both are found in the same eyepiece field. The northern object is NGC 1549 for which I noted: "Has a very bright oval core with extensive round halo. It is set in a "y" shaped asterism of magnitude 10 stars and looks pretty." NGC 1553 in the south of the field has a "very elongated disk with bright oval core and extensive oval halo. There is a suspiciously bright star located very near the core." Sadly, it was not the supernova discovery I hoped I might have made, as it showed clearly on the image of the galaxy in my Deep Space CCD Atlas. Damn! Still they make a fine pair of galaxies. Just under one degree northeast is the bright spiral galaxy NGC 1566 which shows excellent detail in larger apertures. I noted: "A large face-on spiral galaxy with bright oval bar, from which two "s" shaped arms emerge and can be traced well round the galaxy."
We are now right at the northwestern edge of the Large Magellanic Cloud (LMC). If an observer's Nirvana exists anywhere, in my opinion it is the LMC. I have spent many happy months locating and studying the hundreds of fascinating clusters, nebulae, star clouds and stellar associations in this astonishing satellite of our Milky Way galaxy. In fact, there are so many that the real problem is to avoid getting lost in the maze! Even though we are confining ourselves to the larger and brighter objects, there are so many in the LMC that we will need to spend a couple of months on them. The biggest problem is finding a good enough chart. Sadly, once again, Sky Atlas 2000 shows the outline of the LMC but only marks seven objects, making it virtually useless. By contrast, the Herald Bobroff Astroatlas, being produced in Australia, devotes no less than fourteen charts at differing scales to the LMC and offers a wealth of detail. If, like me, you get hooked on the LMC, you will find the HB atlas invaluable.
There are a few aspects of the LMC that are useful to know before starting to observe it. Most people look at the biggest and brightest object - The Tarantula Nebula - then ignore everything else. Why? Perhaps because the profusion of objects confuses them. It is easy to have this happen unless you know something about the structure of the LMC. For our purposes the major structural features are:
The main axis of the galaxy - the so-called "Bar" - which crosses the Cloud from north-west to south-east and contains most of the multitude of small clusters and other features in a broad band of confusing detail.
The so-called "wings" that rise north from the Bar at the eastern end and north and south of the bar at the western end. The 'wings" contain most of the larger, bright groupings of objects, including many of those we shall be looking at.
In addition, be aware that the numbering of NGC objects is rather overdone in the Magellanic Clouds. Often what appears to be a single complex object can have up to seven different NGC and IC numbers allocated to almost indistinguishable, tiny sections within the object. It is a great challenge for experienced observers to try to identify every catalogued item, but we shall be content for now to find the large, bright complexes and look at them as a whole. When you consider that the LMC is over 160,000 light years away, you realise how extraordinarily large and bright these complexes must be.
Let us start our exploration of this wonderful area high in the northwest wing, where we find the bright complex catalogued as NGC 1760/63/69. It is a prominent group of three closely placed patches of star clusters and nebulosity surrounding a small star cloud. In the centre of the star cloud is the variable star HV5499 which appears to have a tiny nebula around it. Is it possibly a planetary or proto-planetary nebula? It is not catalogued as such in any text I have. The whole area brightens well with the aid of an O-III filter and is surrounded by many fainter objects that make a bright and interesting field. Moving south into the Bar we find another complex marked as NGC 1737/43/45/48. Again, four small clusters (the one on the west end is fan-shaped) are surrounded by bright nebulosity and make a fine sight, being closely grouped in a bright field.
Back north in the direction of NGC 1763 but nearly two degrees to the east lies the bright oval open cluster NGC 1818. In larger apertures the cluster is well resolved with distinct star patterns and bright outlying stars. It is so bright and well resolved it could be taken for a Milky Way cluster, but is in fact an LMC object. Moving south again towards the Bar we encounter the bright area NGC 1850/54/58, containing three clusters. NGC 1850 and 1854 are to the west and are condensed but will resolve in larger apertures. NGC 1858 to the south-west of the field is a large star cloud surrounded by bright nebulosity with emission areas and other structure that lights up brightly with an O-III filter. This is a most interesting area. Moving less than one degree southeast and right into the bar we find the large open cluster NGC 1903. This appears as a round haze to smaller scopes, but larger apertures will partially resolve it, showing a dense round core surrounded by a wide edge. It looks very much like a small globular cluster. Lying in the Bar, it is surrounded by numerous other fainter clusters close by.
Our final object for tonight is an excellent navigation mark, being prominent and almost at the centre of the LMC. It is NGC 1910, and is almost in the field of 1903, slightly to the northeast. NGC 1910 is a massive U-shaped star cluster, well resolved by larger apertures and containing the bright 7th magnitude variable star S Doradus. The cluster is surrounded by a complex nebulosity which contains many dark lanes and has a definite 'S'-shaped outline that is enhanced by an O-III filter. It is a magnificent area and an excellent point at which to resume our tour next month.