Roaming the Deep Sky #11

Markarian’s Chain
By Don Clouse

Spring brings the constellation of Virgo to prominence in our evening night skies. When our gaze is directed toward northwest Virgo, we are staring into the heart of the Local Supercluster of Galaxies – also referred to as the Coma-Virgo Supercluster. We are also looking nearly directly up out of the plane of our Milky Way Galaxy. The bulk of the Virgo (for short) Supercluster lies between +70 and +80 degrees galactic longitude – quite near to the north galactic pole. An observer looking back at us from the Virgo Cluster (the center of the Virgo Supercluster) would see a large, bright, beautiful, nearly face-on barred spiral galaxy accompanied by some small companion galaxies – the Magellanic Clouds. Our Milky Way Galaxy and our Local Group of galaxies are also a part of the Local Supercluster. Quite possibly, M31, the Andromeda Galaxy, its brighter satellites, M32 and M110, and M33, the Triangulum Galaxy would be visible in the same field of view with the Milky Way and its satellites! Fittingly, we are treated to a similar view when we train our telescopes on a group of galaxies near the center of the Virgo Cluster (and thus the Local Supercluster also) known as Markarian’s Chain (in the upper right corner of this DSS image). Nine galaxies are visible in a 50’ field of view and eleven in 1.1 degrees. These galaxies are all thirteenth magnitude and brighter. Before taking a closer look at some of these galaxies, let’s first locate Markarian’s Chain on the sky.

Refer to chart 1 (galaxies to 11^th and stars to 9^th magnitude). It shows the location of several galaxies including M87, M86, and M84 near the center of the chart. Note that several Messier galaxies, 16 to be exact, are shown. These are all members of the Virgo Cluster. Most, if not all, of the other galaxies are members of the Virgo Cluster also. M87, while not a member of Markarian’s Chain, is the brightest, as well as the gravitationally dominant, member of the Virgo Cluster – which lies at the core of the Local Supercluster. At magnitude 8.6, it may be visible in a large finder like an 8x50. Also, at magnitudes 8.9 and 9.1 respectively, M86 and M84 could well be visible in a large finder as well. All three galaxies lie on a line between Epsilon Virginis, Vindamiatrix, and Beta Leonis, Denebola. Vindamiatrix is the star at the top of the large kite or diamond shaped asterism in Virgo. (The first magnitude star Spica is at the base of the diamond.) Denebola is the tail of the lion, the eastern most star in the traditional constellation lines of Leo. At magnitudes 2.8 and 2.1, respectively, the two stars are easily visible to the naked eye. M87 lies about 2.5 degrees closer to Vindamiatrix. However, M86 lies almost exactly between the two. Put in your lowest power eyepiece, then try pointing your telescope directly between the two stars using a Telerad or other "1x" pointer. If your pointer is well aligned and you’re lucky or good, you just might put Markarian’s chain smack in your eyepiece. Otherwise, M86 and M84 may be visible in your finder especially if it’s an 8x50. I haven’t yet tried spotting this pair in my finder-scope. However, I fully expect to be able to do so on a sufficiently good night with the 9x60 finder.

Once you locate M86 and M84, use chart 2 (galaxies and stars to 13^th magnitude) to identify the other galaxies in the field. The circle shown is 50’ (arcminutes) or 5/6 of a degree. For comparison, recall that the full moon averages about one-half degree (or 30’) in size. The 50’ circle, not coincidentally, is the field of view I get with my 35mm eyepiece in my 8" SCT (Schmidt-Cassegrain telescope). {A quick primer: 2032mm telescope focal length / 35mm eyepiece focal length = 58 power. 49 degree eyepiece apparent field / 58x magnification = 0.84 degree true field of view. 0.84 degree = 60 minutes per degree x 0.84 degree = 50.7’} These nine galaxies make for a stunning sight in a single field of view. However, this 50’ field is rather tight and a couple of the galaxies end up right on the edge of the field and can be difficult to pick up. A full one-degree field would be better. In fact, I’m anxious to try my new 40mm (62 degree apparent field) 2" eyepiece on this group. Given a dark, transparent night/site, I should be able to bring NGC4458 and NGC4461 into the 1.2-degree field this eyepiece will provide - for a total of eleven galaxies! What can you expect these galaxies to look like?

A description of how the nine galaxies appeared to me using my 8" SCT follows. These observations were done on an exceptional, very transparent night in May 1999 at a site about one mile southeast of the Curby site. Some of the observations are at 58x and some at 101x. The 101x field of view is much smaller than the 58x field; thus not all nine galaxies were visible at the same time. Higher powers can bring out additional detail. Try observing some of these galaxies at 100x to 150x while you’re there – or even 200x or more with an excellent night and a larger scope. What additional detail do you pick up at higher powers?

• M84 – 101x: Bright, non-stellar core. 3’ in diameter.
• M86 – 101x: Bright, extended core, perhaps 0.5’, surrounded by a bright 2’ diameter haze which falls off in brightness rather quickly. Maybe 3.5’x3.5’ overall.
• NGC4387 – 101x: Very small and dim. Perhaps 1’ in diameter. Slight brightening toward the center.
• NGC4388 – 101x: Aligned east-west. Relatively dim. Perhaps 3’x1’, with very slight brightening toward center.
• NGC4402 – 58x: Very faint smudge. Elongated, 2’x1’.
• NGC4413 – 58x: Another small, faint smudge. Barely there.
• NGC4425 – 101x: Concentrated, but non-stellar core. Dim, hazy, and small.
• NGC4435 – 58x: Relatively bright, stellar core. Very small, circular, with an apparent, surrounding haze.
• NGC4438 – 101x: Elongated NE-SW, 4’x2’. Relatively dim with an indistinct core.

Table 1 lists some data on the galaxies shown on the second chart. This data is an amalgam of information complied from the sources listed at the end of the article and represents the "majority opinion", or an approximation thereof, where details differ among the sources – and they do, considerably in some cases.

Both M86 and M84 lie near the gravitational center of the Virgo Cluster. M86 is in the vicinity of 50 to 60mly away. If it is 50 million light years (mly) distant then it is 175,000 light years (ly) in diameter – a very large galaxy indeed. If both M84 and M86 are at 50mly, then they are only 300,000 ly away from each other. However, this is considered unlikely since giant ellipticals tend to be somewhat solitary objects. Additionally, M86 has a high blue shift meaning it is moving in our direction. This in turn means that it is likely to be nearer to us than is M84.

Long classified as an elliptical galaxy, there is now evidence that M84, like M86, may be a face-on lenticular galaxy. Lenticular galaxies (type SO) are similar to ellipticals in that they contain very little gas or dust and consist primarily of older stars. However, rather than having a spherical or football shape, they consist of a large central bulge and halo surrounded by a smooth flattened disk of stars with no spiral shape. Some even have large bars (type SBO). If M84 is 65mly away, then it is over 100,000 ly in diameter – another very large galaxy.

Markarian’s Chain actually extends well beyond what is shown on Chart 2. One source extends the chain on to the northeast to M88 – a whopping 2.4 degrees. This adds NGC’s 4459, 4473, 4474, and 4477 to the line-up – all brighter than 13^th magnitude. If you have a large aperture telescope, you may be able be pick up several fainter galaxies in the close vicinity of Markarian’s Chain. So, if you have the opportunity this spring, try observing Markarian’s Chain. How many galaxies can you see? A low power, wide field of view is a very rewarding sight. You’ll be glad you tried it.

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