Object of the Week September 15, 2013 - NGC7678 aka Arp28

NGC 7678
UGC12614
Arp 28

Pegasus

RA 23 28 27.9
DEC +22 25 16

Type: Galaxy SAB(rs)c

Size 2.3’ x 1.6’

Mag: 12.7

Approximately 140million light years away and nearly dead center in the Great Square of Pegasus lies this weeks OOTW. NGC7678, also known as Arp 28, is a spiral galaxy with what Halton Arp called a “heavy arm”. NGC7678 has an asymmetric appearance in photographs and the eyepiece. A beautiful face-on spiral, its southernmost arm is quite more dramatic than the others which may be caused by intense star forming regions.

Rather easy to find the field, NGC7678 lays 1.2˚ southeast of 4.4 mag Upsilon Pegasi. The galaxy itself is nicely framed within a trio of 12^th magnitude stars creating a triangle.
In my 25 and at low power, I find the galaxy is a rather large diffuse glow with a brightening at its southern end. At 300x and higher, I observe a bright non stellar core as well its arms. The heavy arm also starts to stand out much more apparently at higher power. NGC 7678 itself should be readily visible in scopes down to about 12” but high power and good skies may be required to distinguish this galaxies’ notable feature.

One other interesting little tidbit, NGC 7678 has been rather active as it’s been a host for 3 supernovae in the last 16 years, with the most recent occurring in 2009. None of the 3 most recent supernovae occurred in the heavy arm. All occurred on the opposite side of the galaxies core. The three supernovae were:

2009ga reaching 16^th mag
2002dp reaching 15^th mag
1997da reaching 18^th mag.

So as Pegasus rides high in these September skies, look for NGC7678 in the relatively empty area of sky near the center of the Great Square of Pegasus. You may just be surprised at what you can see!

And as always:

“Give it a go and let us know!
Good luck and great viewing!”

Attachment 893

Observing this galaxy as part of my Herschel 2500 survey in October of last year, I recorded (16", blue-zone site, fine conditions):

The Herschel NGC 7678 near Nu Peg is the starburst Arp 28. It is visible at 45x and appears rather strongly elongated just inside a triangle of stars. 225x leaves it only slightly elongated NS. At this magnification it shows almost no overall concentration but shimmers tantalizingly, offering what seems to be glimpses of a core and an EW bar connecting to a slightly oval ring that defines the periphery of the galaxy. There seems to be an enhancement along the ring to the SW, and a faint star on the NW edge of the core. All these specific features are uncertain but seem to be glimpsed consistently.

EDIT: Dragan, you are right of course. I misread the chart in the dark. The nearby bright star is indeed Upsilon and not Nu Peg.

Dragan,

cool reminder, thanks. I have definitely revisit Arp 28 with my 27".

With my old 16" the "heavy arm" was quite obvious.

16", 200x, NELM 7m+
http://www.deepsky-visuell.de/Zeichnungen/NGC7678.jpg
inverted version

Great sketch Uwe!

Very nice galaxy! Impressive in all respects. It was a joy to observe in my 18", and I definitely liked its field, with the galaxy framed nicely in that star triangle. I could readily detect the heavy arm, which at moments of bad seeing kind of reminded me of the view of M51 and its companion in a small instrument. I did note that the galaxy core seemed to be encircled in an outer glow with a darker 'ring" sourrounding the nucleus, though the feature was low contrast, and I wonder if it was more the result of contrast from the nucleus and the heavy arm. I plan to have another go in it next weekend...

Attachment 906

When this object was first posted I checked my notes to see if I'd observed it, and sure enough I had one observation from several years ago. But it was immediately apparent from my sketch that I'd observed the wrong galaxy (!) so I set out to observe NGC 7678 correctly a few weeks ago. My notes:

"This is a beauty - two spiral arms, with the southern arm being obvious and straight and with a knot near one end. The northern arm is much more subtle, but the stellar core is easy to see and gives this faint spiral a definite center to spin around. The bright arm hooks a little as it bends toward the core but neither arm can be followed all the way to the core. Lovely sight! 408x, 21.59 SQM.

Attachment 946 Attachment 947

Being bracketed by a triangle of relatively bright field stars helps make 7678 an object to return to. When my observing companions saw it in my scope they went back to their own scopes and enjoyed the views just as much in their 16" and 24" Dobs.

Quote:

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Originally Posted by Howard B

"This is a beauty - two spiral arms, with the southern arm being obvious and straight and with a knot near one end. The northern arm is much more subtle, but the stellar core is easy to see and gives this faint spiral a definite center to spin around. The bright arm hooks a little as it bends toward the core but neither arm can be followed all the way to the core. Lovely sight! 408x, 21.59 SQM.

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Howard, I also took at NGC 7678 earlier this month with my 24-inch and noted the more prominent southern arm "brightens right at its western tip." This feature (shown nicely on your sketch) isn't prominent on images, but is probably a brighter HII complex.

I observed this galaxy last night (far from a perfect observing night). The galaxy is nicely framed by the triangle of stars and appears at first diffuse with some mottling in it.

The easiest feature is the stellar-like nucleus which was relatively easy and appeared consistently. Further structure in the halo consisted of the southern arm, which could be separated from the inner part. The end of the arm appeared brighter, but like a short thin bar rather than round. Of the northern arm, only the beginning was visible as a short and relatively broad extension from the innner core into the fainter halo.