exotic

March / April

NGC 4216 and Friends

3x edge on in the Virgo-Cluster

12 15 54    +13 08 58

This is a beautiful galaxy trio at the western border of the Virgo cluster, some one and a half degrees south of M98. 

NGC 4216 is the middle and with mag 10.3 brightest member of this group. It is roughly 8' long and an easy target. The two neighbors to the left and right become increasingly fainter. The SW neighbor  NGC 4206  is only mag 12.0 and with 6' a bit smaller. The NE neighbor NGC 4222 finally is only mag 13.2 and is only 3' long. Depending on the size of the telescope and sky conditions, the latter two appear as more or less well defined, highly elongated patches that become hardly brighter toward the center.

NGC 4236

A huge but faint edge-on galaxy in Draco

12 16 41   +69 28 09

NGC 4236 belongs to the M81 group and is a barred spiral seen edge-on. At the eyepiece, this galaxy is bizarre and is easily overlooked when sweeping over it. It's integral brightness of mag 10.5 should actually make it a distinct object. The light is spread, however, over a length of more than 20'. This yields a low surface brightness and ghostly appearance of this galaxy, somewhat similar to that of NGC 247 of the Sculptor Group (at least from our mid-European latitudes).

Visually, only part of the entire galaxy is distinct, corresponding to the central part in the image. The galaxy appears mottled and both in the northern and southern part several HII regions are visible as more or less distinct condensations.

Markarian 205

The puzzle about quasi-stellar objects

12 21 43 +75 18 38

Mrk 205 is a an object with a long history. Despite the extremely different red shifts of Mrk 205 and NGC 4319, Halton Arp suspected a "bridge" between both objects, implying that they are close in space to each other and not a chance alignment along our line of sight. Arp was considering the hypothesis that the considerable red shift of the then new quasi-stellar objects or short quasars was not due to their distance from us. Instead, he suggested that they are objects being expelled from the nuclei of their "host galaxies" and that the red shift of their light had other reasons (such as, for instance, gravity). This was in strong disagreement to the general view of the scientific community, in particular Allan Sandage, leading to lasting controversies between the supporters of the two  groups (with Arp's  being certainly a minority).

Visually, Mrk 205 is certainly not easy, but can be glimpsed already with a 14" and indirect vision. It is a bit off set from the core of NGC 4319, of which only the central part is visible. With 22", Mrk 205 is visible directly as a stellar object.

NGC 4449

A starburst galaxy in Canes Venatici

12 28 11   +44 05 33

NGC 4449 used to be a barred spiral before it became involved in gravitational interactions with neighboring galaxies of the M94 group. Heavily battered by this interaction, it looks now like the Large Magellanic Cloud rather than a barred spiral. As a consequence of this interaction, the galaxy is strewn with new star forming regions with young bluish cluster and red HII regions.

At the telescope, NGC 4449 is quite bright and highly structured, such that it bears high magnifications and allows spotting the condensations quite well.

3C 273

The brightest quasar in Virgo

12 29 06    +02 03 08

3C 273 is an entry of the Third Cambridge Catalog (3C) of radio sources. Its optical counterpart was the first quasar of which Maarten Schmidt discovered the spectrum to consist of almost 16% red shifted HII emission lines. Quasars are galaxies with extremely bright nuclei, where matter spins on an accretion disk into a central Black Hole. The red shift of 3C 273 of z=0.158 corresponds to a distance of 2.4 billion LYs.

At the telescope,  3C 273 appears as a stellar object of brightness mag 12.8. The absolute brightness of the quasar, however, is roughly 300-fold larger than that of our entire Milky Way. The jet, pointing to SW and visible in the SDSS image, is not within visual reach.

Carsten Strübig

Finder chart

M87 and its jet

Relativistic outflow of a cD monster galaxy

12 30 49 +12 23 28

M87 is the central galaxy of the Virgo Cluster. It has a brightness of mag 8.6 and belongs to the elliptic cD giant galaxies, that swallow up over time their entire neighborhood. M87 is identical with the very strong radio source Virgo A. In the middle of M87, scientists expect a super massive Black Hole of about 6 billion solar masses, that is surrounded by an accretion disk of incident matter. Out of this center of the galaxy emanates a jet of mater at relativistic speed, that emits broad-band polarized synchrotron radiation. This jet is presumably collimated by strong magnetic fields of the accretion disc and the rotating Black Hole itself.

In March 2009 in a night of excellent seeing, I was successful already at my first attempt. With low powers there was first the familiar image of M87, that is visually not particularly interesting and does not knock your socks off. M87 belongs to the more boring galaxies, as there are, typical for an elliptic cD galaxy, hardly any structures visible.

Increasing the power to 400x, the jet was relatively easy to discern as a short and thin appendix to the core of the galaxy. The length was only 20", in agreement with the literature. During a prior observation of Saturn at the same power, I had tried to memorize this dimension in order to get an estimate of what to expect. As to be expected, structures within the jet were not visible with my Dob. Using the small background galaxies (the small PGC galaxies, not the much brighter and larger NGC galaxies!), I could further verify the correct orientation of the observed structure. These faint galaxies can be helpful under less than optimal conditions and borderline observations.

I presume that a successful observation of the jet depends largely on the seeing. The jet is very small and merges into the glow of M87 under sub-optimal seeing. On the other hand, you will not need particularly dark skies, as the core of M87 in the "background" is bright anyways. This was confirmed during later attempts at this object. During at least 6 occasions, I was successful only twice, always at very good seeing.

Altogether, this is a very interesting story, astrophysics live at the eyepiece. Is there any other way to get closer to a Black Hole?

More about the jet of M87 is here.

NGC 4676

The Mice in Coma Berenices

12 46 00 +30 44 00

The Mice, NGC 4676 A/B, is a faint and small pair of galaxies, listed as entry 242 in Arp's catalog of peculiar galaxies. It therefore takes some time to discern the details within this pair.  With my 22" Dob, the tidal streamer to the North is not particularly difficult and extends over roughly twice the diameter of the northern component. At the opposite side, there is as well an extremely faint brightening. This is presumably the inner arm of the southern galaxy.

LoTr 5

A hint of a PN in Coma

12 55 33 +25 53 30

Longmore-Tritton 5 is one of the very large PN and, at least as compared with most of the other members of that illustrious list, it is an "easy" object with OIII filter (only very faint instead of extremely faint  ).

I have observed this PN already several times under various conditions. Under fair skies, it is difficult to separate the diffuse glow of this PN from stray light of its mag 8.9 central star, even with OIII filter. Under excellent conditions, the PN reveals a faint disk with well defined edge towards S, coinciding with the weak star in between the central star and the bright star S of it. Under such conditions, it is also visible using the UHC filter, albeit with somewhat lower contrast.

NGC 5985 and Friends

The Draco Trio

13 08 12 +41 40 34

This is a wonderful galaxy trio at a distance of 100 to 130 million LYs, that is very interesting already with medium sized telescopes.

The three galaxies of this trio couldn't be more different: NGC 5985 is the easternmost of the three and almost a face-on SBb spiral with brightness mag 11.1 and a diameter of 5'. NGC 5982 is in the middle and is an elliptic galaxy with brightness 11.3. The westernmost galaxy, NGC 5981, is an Sbc spiral seen edge-on. At a brightness of 13.6, this is by far the faintest of the three and in smaller telescopes the most difficult.

Finder chart

M53 and NGC 5053

Two extremely different Globular Clusters in Bootes

13 13 00   +18 10 00

These are two extremely different globular clusters that are in the same low power field somewhat to the W of Arktur.

Both globulars are at a distance of roughly 60 000 LYs. They are therefore not a chance alignment along our line of sight, but really neighbors in space. Their very different appearance is therefore entirely due to their differing size and structure and not due to differing distance.

M 53 is a relatively well concentrated globular (class V in a classification ranging from I (very concentrated) to XII (loose) ), while NGC 5053 is considered class XI. NGC 5053, on the other hand, is considerably more difficult than implied on the POSS image to the left, and does not look at all like a globular! It has a brightness of mag 9.8 and consists of roughly 3 500 stars, of which the brightest reach mag 13.8. "Normal" globular clusters have several 100 000 stars! NGC 5053 is easily overlooked also with a large telescope, as it does not appear as a globular but rather like a very faint, grainy glow, with the brightest stars being already resolved.

More about this very odd couple is here.

Hickson 68

One of the brightest Hickson Groups in Canes Venatici

13 53 41     +40 20 00

Together with HGC 44 in the head of Leo, HCG 68 shares the attribute of being the brightest Hickson Group. Component c displays as a face-on spiral a nucleus with a halo, that appears structured in larger telescopes. Components a and b are S0 and E2 galaxies, respectively, with a brightness of mag 12 and hence not a problem even for smaller telescopes. d and e are a bit more difficult, as they are smaller than 1 arcminute and reach only mag 14.

As you are already in the area: Take a look as well at NGC 5371, a bright spiral 30' ENE of HCG 68 (see image).

NOAO/AURA/NSF

M 102 / NGC 5866

Lateral view of a fine dust lane in Draco

15 06 29 +55 45 47

The assignment of M102 to NGC 5866 in Draco is reported to be not unequivocal, as Charles Messier did not indicate a precise location of this entry in his list.

This probably does not matter a lot to this galaxy, which is a beautiful sight in the eyepiece, be it with or without Messier number. This galaxy is a prototype of a bright lenticular galaxy of type S0. The most interesting feature is the very fine dust lane crossing its body, requiring good seeing for resolution. If you happen to have such good conditions, the dust band is visible first as cutting through the core of the galaxy, its central bulge. There is the an interesting visual effect, if you follow the dust lane to the ends of the edge-on galaxy, as these fainter extensions of the galaxy appear to "compete" with the dust lane, resulting in a kind of blinking effect.

AGC 2065

Corona Borealis Cluster

15 22 42   +27 43 21

This is the famous Corona Borealis galaxy cluster Abell 2065 (1.5 Billion LYs distance), which used to have this mystique of being not observable. In Burnham's classic, it is classified as out of reach for amateur telescopes. Well, amateur telescopes have changed since then and in April 2007, I gave it a try.

The brightest galaxies of this cluster are not brighter than mag 16.5. Of course, these galaxies are not as densely packed as in some of the Hickson Groups, but nevertheless, 300x was necessary with my 22" Dob to separate things. Three galaxies were discerned with certainty (No. 1, 3, and 6 on the map on Steve Gottlieb's page, see below), two of which (1 and 6) could be held quite steadily with indirect vision. With some of the other galaxies, such as 2 and 4, I was not fully sure, as there are faint field stars in the area which were not separated with absolute certainty.

More about this cluster is on the page of Steve Gottlieb and Jim Shields .

Seyfert's Sextet

Five galaxies and a tidal plume within 2 arcminutes

15 59 11   +20 45 45

Hickson 79 alias "Seyfert's Sextet" is the absolute showpiece of the extremely tight Hickson groups. Five galaxies and a tidal plume squeezed into a horseshoe of only 2 arcminutes.

The group itself is visible already with medium sized telescopes. Separation of the tight swarm into individual knots requires, however, high power (400 - 600x). Hence you need aperture to be able to see these tiny galaxies of mag 15 to 16 at such high power at all.  With my 22" Dob, the group is first resolved into three knots (a, b und c), which are, however, difficult to hold steadily. Every once in while in good moments, b and d appear resolved as well.