0
Small Wonders: Andromeda
Mar 18 2005 09:24 AM |
Tom T
in Small Wonders
Discuss this article in our forums
|
Small Wonders:
Andromeda
A Monthly Guide to the Night Sky by Tom Trusock A printable version can be found here.  Wide field Chart
  Far from resembling a Princess, I've always seen Andromeda as a cornucopia arriving just in time for harvest - whichever way you see it, it contains a wealth of spectacular deep sky objects. Mention Andromeda to nearly any amateur astronomer, and immediately an image of the stately Andromeda galaxy and it's companions comes to mind. While there's much more in this constellation, there's no denying this is one of the all time best showpieces in the night sky. M31 the Great Galaxy in Andromeda and close satellites...   The Andromeda
Galaxy (also known as M31) is notable for several reasons but, perhaps
it's best known for being one of the keystones in
resolving the Island Universe debate (are there many galaxies or just
one?) , and determining interstellar distances by the use of Cephid
variables.At the turn of the century, astronomers questioned if spiral nebulae like M31 were located inside the Milky Way galaxy or external to it. Then, in 1923, working with the 100 inch telescope at Mt Wilson, Edwin Hubble imaged stars in the halo of M13, discovered the existence of Cephid variables among them and came up with a distance of 900,000 light years - far beyond what most believed the limits of our galaxy to be at the time. In 1944, German born astronomer Walter Baade - who had been classified as an enemy alien and thus not able to work on defense projects, was "stuck" working at Mt Wilson. Due to the wartime blackouts of Los Angeles, Baade was able to make good use of the blackest skies Mt. Wilson will probably ever see to resolve the individual stars throughout M31. Although these astronomers studied M31 with the most powerful telescopes of the time, it's visible to the naked eye under all but the worst conditions of light pollution. Andromeda - the 31st entry in Messiers catalog, spans around 5 degrees under the most careful measurements, and is an astounding 2.2 to 2.9 million light years away, and is in close attendance by m32 and m110. Somewhat farther out, in Cassiopeia, can be found two more bright Andromedean satellite galaxies - NGC 185 and NGC 147. It's fun to experiment with different optical aids on Andromeda - it's so large, it makes an excellent binocular target, but I've often found the best views to be in a 4" scope - this tends to frame the brighter portions quite nicely, and reveal M32 and M110 as well. When looking for M32, look for a brighter tighter puff closer into M32 itself, while in a small scope M110 is far more ephemeral puff of smoke. My 8" reflector on a decent night easily pulls in one of the dark lanes visible in photographs, and a larger scope will show both dust lanes. We aren't completely done with the Andromeda galaxy - we'll return to visit it's brightest globular cluster in the form of our challenge object this month but for now, lets move on. Gamma, NGC 752, Beta and the Ghost...  Gamma Andromeda First, lets start way out on the tip of the horn - consult your wide field chart to find Gamma Andromeda. This is a nice bright double that easily shows up in a small scope. Even though you might split it with a low power, be sure to try a succession of higher powers. One thing that I've found is that star colors often seem to change a bit with the magnifications used. Gamma is a good example of this effect. At lower powers I found both stars to have a orange hue, but when I increased the magnification to 70 power in my 4" refractor, I found the brighter one remained orange while the dimmer one took on a whitish hue. What do you see? NGC 752 Next, with your widest field eyepiece, scan eastward from gamma and look for a large open cluster. This is NGC 752, and it's best seen in binoculars or a wide field scope due to it's large size. In my 4" scope, I found my best views at 36x where I counted a couple of dozen stars. Look for two bright golden stars in the field lying just outside the cluster proper. Similar magnitude and coloration stars such as these two often remind me of eyes peering back at me out of the night. Beta Andromeda (Mirach) and Mirach's Ghost (NGC 404)   Now head back up the base of Andromeda, till you come to beta. Take a moment and study beta carefully - you'll notice something that looks like a reflection on the lens of your eyepiece. Unless you are looking very closely for it, you might miss it completely. This is the galaxy known as Mirach's Ghost - NGC 404. More advanced observers might decry the fact that it's next to impossible to separate NGC 404 from the glare of beta - unfortunately, they are quite right. Fortunately for us though, there's not much to see in any size scope. The success here lies in finding the galaxy and recognizing it for what it is rather than discarding it as a reflection or trick of the light. The Blue Snowball...   This one is a bit more difficult to hop to. The key lies in the three bright stars that are oriented mostly North to South in the above map. From a semi-dark site, they are naked eye stars. If you can see them, the hop shouldn't be that bad. If you can't, you'll have to get to the area using the wide field map, then narrow in with the above one. 7662 - the Blue Snowball is CERTAINLY worth the effort. I noted that it was non-stellar at 37x in my 4" refractor, and recall it as being an amazing shade of blue in both my 8" and 4" scopes. It's a planetary nebula, and remember these can support high powers so now's the time to pour it on. You may also want to haul out a UHC or OIII filter as well to increase contrast and see how the image changes - don't expect a lot with this particular target and a small scope, but it's a good habit to get into. NGC 891 - The Outer Limits Galaxy   While I've spotted 891 in my 4" scope, it takes an 8" or larger scope to really begin to appreciate it. One of the first TV stars (It was in the opening of the show "The Outer Limits" hence the name) it's a truly spectacular galaxy in a larger scope. In my 8", it's typically a nice spindle of a galaxy, with the dust lane only beginning to show itself when I'm under the best sky conditions. In a 15"-20" scope, it begins to look like the picture to the left. Because it's an edge on galaxy, it's one of the few galaxies that respond well to the Collins I3 image intensified eyepiece and is simply spectacular when viewed in such a device. G1/Mayall II   While it's not a
toughie to see - if you have sufficient aperture - it can be a real
pistol to find.Conceptually, this is a spectacular target. Visually, it's something less than impressive. We've looked at several globulars in our own galaxy by this point - now it's time to take a peek at the brightest globular in the local group. The catch? It's not in our galaxy. It's in Andromeda. The shot to the right was taken by the Hubble Space Telescope. It's called G1 or Mayall II and orbits the Andromeda Galaxy at a distance of 130 thousand light years from Andromeda's center What's truly amazing is that you can actually make out some extent to G1 through a moderate sized back yard telescope. It's not just a point source. While you are a long long way from resolving any individual stars, you can clearly see that there is something there - especially when you compare it to the two foreground stars that flank it. At mag 13.7, it's a somewhat dim target though, so the more aperture you can throw at this, the better your chances of finding it. It's certainly doable in a 10" scope from a decent site, and more than likely is cacheable in an 8" scope from a very dark site. I've even heard rumors of folks grabbing it in a 6" scope.  I always start my
star hop at M32, and work straight down to the very recognizable
asterism shown at left. Then I work my way over towards G1. Once
I know I'm in the right area, I crank up the power and begin inspecting
multiple stars in the area. G1 lies almost in the middle of two
similar magnitude foreground stars, and that's a big help when it comes
to fishing it out.Here is a finder chart that may help. I've flipped the image in this chart to aid star hopping at the eyepiece.   Note the circled
grouping of stars in the chart above
- in a moderately sized scope, this grouping bears a strong
resemblance to Cassiopeia. Once you are in the right area, look
for three stars at the position marked G1 on the charts. Under
high magnification, it will resemble Mickey Mouse - the two foreground
stars are the ears, and Micky's head is G1.The DSS image to the right should resemble what you see. Be sure to pump up the magnification, and you can see that it's not quite a stellar point. Not very spectacular visually, but it blows my mind when I think about exactly what I'm looking at. While I've caught it in my 10" and seen extent in my 15", the best view I've ever had of this object was when I was observing with Gary Gibbs in his 20" with a Collins I3 image intensified eyepiece. You could obviously see that it wasn't a star - in fact, it had a star like core with a dimmer coma around the outside and reminded me of tiny dim Milky Way globulars I've caught in a small scope. If you grab this one, you can rest assured that your star hopping skills are getting quite good, and you've seen a target very few others have. I'd
love to hear of your experiences under the night sky - please feel free
to
e-mail me or send any observing reports to: tomt@cloudynights.com Please indicate if I can cite your observations in future columns. Photographic Images Courtesy DSS (except where noted): copyright notice http://archive.stsci.edu/dss/acknowledging.html Star Charts Courtesy Chris Marriott, SkyMap Pro 10 Printed with Permission http://www.skymap.com |
0 Comments