6 Attachment(s)
Object of the week 16 October 2016: NGC 1023 (Arp 135), a hidden gem in Perseus!
Object of the Week, 16 October 2016: NGC 1023 (Arp 135), a hidden gem in Perseus!
NGC 1023 = Arp 135 = UGC 2154 = CGCG 523-83 = MCG +06-06-073 = PGC 10123
RA: 02h 40' 24"
DEC: +39° 03' 46"
Type: SB(rs)0-
Size: 8.7' x 3.5'
P.A.: 87°
Mag: V = 9.4, B = 10.4
On glorious fall evenings, the jewel-like stars of the constellation Perseus, the Hero, dominate the sky. All skywatchers turn their scopes and cameras to the glorious Double Cluster, the Demon Star Algol, to the superb Little Dumbell Planetary (M76), or the beautiful open cluster M34. Even the faint and challenging California Nebula gets a fair share of attention. Yet, hidden amongst the Hero’s bright stars and popular deep sky objects, is a real gem of a galaxy, that few people are aware of: NGC 1023, also known as Arp 135.
I personally “discovered” this galaxy last August, during my ongoing attempt to survey as many as possible from the galaxies in Halton Arp’s famous catalog. Actually, I should say, I “re-discovered” it, for I had read about this galaxy years ago in Steven ‘O’Meara’s “Hidden Treasures” book, but somehow I managed not to observe this superb “hidden treasure” until now. This galaxy is indeed not well known. A search in the internet reveals rather few amateur photos of it, and even fewer observations. I asked several local friends if they have ever observed it, and none was aware of it, yet some of them knew very well NGC 1275, a much more difficult galaxy in Perseus!
Attachment 2304
A DSS image of NGC 1023 and 1023A
So, what do we know about this “unknown” galaxy? NGC 1023 is a barred lenticular galaxy, approximately 34 million light years away, and belongs to the NGC 891 group of galaxies. It has a visual magnitude of 9.4, with a very bright core surrounded by a rather faint halo, giving it overall dimensions of 7.5x3 arc minutes. Astrophysically, it has a very rapidly rotating nuclear region, suggesting the presence of a massive black hole. Also, a large population of globular clusters has been detected, including some very large ones which appear to be similar to the globulars of M31. Halton Arp included NGC1023 as the 135th entry in his “Catalog of Peculiar Galaxies” as “an elliptical galaxy with nearby fragments”. The only nearby fragment appears to be NGC 1023A, a very faint diffuse irregular system located on the southeast edge of NGC 1023. Arp suggests that PGC 10169, a bit further to the east, may be another fragment. Although both of these galaxies are very near NGC 1023, the appearance of the main galaxy does not show the typical effects of tidal interactions, which are almost certain to have occurred.
Well, enough astrophysics. What can be seen visually? Using my 18”, my first impression on seeing NGC 1023 was that under medium powers it appeared quite similar to how M31 appears at low power in a 4-inch refractor, except that the core of NGC 1023 appeared much brighter. Using a much higher power of 297x, NGC 1023 was an amazing and totally unexpected sight. The galaxy is located in a very beautiful star field of 8th to 12th (and fainter) field stars. It has a very bright almost stellar nucleus, surrounded by a very bright, rhombus shaped core. This in turn is surrounded by an elliptical bright region. It is very rare to see a galaxy showing so much detail in its core area. On close scrutiny, there seems to be a dark area between the rhomboid core and the bright outer region, but I suspect that it might be only a contrast effect, for even in an HST photo such a feature is not evident.
Attachment 2305
Wide-Field Hubble Observation, NGC 1023
What’s more, there are quite long extensions of light on both the east and west sides of the central area. These extensions of light are quite long and wide, and seem to faint into the background sky without the more typical pointed edges. Although these extensions are quite faint and, unlike the central region, of low surface brightness, they are quite easy to detect and trace. On the southeast edge of the eastern extension, the galaxy NGC 1029A is readily detected as a very faint, roundish patch of light. On both extensions some15th to 16th magnitude stars can be detected. I did not see PGC 10169, but I have to admit that at the time of the observations I was not aware of its presence. At magnitude 17.5 it might be detectable in large scopes under very dark skies.
Attachment 2306Attachment 2307
Observations of NGC1023 with 18" dob
NGC 1023 is one of the best galaxies to study in small-sized scopes. The central area of the galaxy is readily visible in low powers in both my 5 and 6 inch refractors, and shows the distinct brightness variations, albeit with lower contrast. Although I did not get a chance to try it, I am certain that the galaxy will be readily visible in the popular 80 to 100mm refractors. Using powers of around 100X in both the 5 and 6 inch refractors I could readily detect the faint galaxy extensions, but I could not detect NGC 1023A.
Attachment 2308Attachment 2309
Observations of NGC1023 using a 6" refractor
As I mentioned above, I could find only a few observations of NGC1023, and most of them agree with what I observed myself. David Tosteson has also observed the “mini M31” appearance and mentions a N-S dark lane, possibly part of the dark area I detected in the central area. Both Tosteson and B. Wilson detected NGC 1023, as did Alvin Huey using his 22”. Neither of these observers mentions PGC 10169.Steve Gottlieb’s observations using 17.5 and 18” scopes are also similar, except that he does not mention NGC 1023A. O’Meara’s observations using his 4” refractor are pretty similar to my observations using five and six inch refractors, but he also mentions that NGC 1023Awas detected in an 11-inch dob by J. Dillon.
For me it is still quite amazing that such a bright and detailed galaxy, in such a popular area of the sky, is not so well known amongst visual observers. I am pretty sure that it might be detectable even in large binoculars, provided the observer can separate the galaxy’s central area from the nearby stars.
So, during the next new moon period, turn your scope to Perseus, zoom in on NGC 1023, and enjoy one of the most beautiful galaxies of the northern sky! And as always,
GIVE IT A GO AND LET US KNOW!
