Object Of The Week, March 20 2016 - Arp 22

Arp 22 - NGC 4027

Galaxy

Constellation: Corvus
RA: 11 59 30.168
DEC: -19 15 54.62

Mag: 11.10

Size: 3.0' 2.1'

Type: SBd

NGC 4027 was discovered by William Herschel on February 7, 1785, who logged it as number 296 in class II, Faint Nebulae. His description (according to his paper "Catalogue of One Thousand new Nebulae and Clusters of Stars") was "pB, pL", though the ncgicproject.org website contains the description "GC, pF, pL, R, rr, st 16".

Attachment 2025

Nowadays this galaxy is known to be part of the NGC 4038 group at a distance of about 83 million lightyears. Other members of the group are the famous Antennae galaxies (NGC 4038 and 4039) and the NGCs 3956, 3957, 3981, 4024, 4027A, 4033 and 4050, as well as several fainter galaxies with UGC or PGC designations. The group is spread out over an area with a radius of about 5º in the sky. Its center lies about 30' east of NGC 4027. So I guess the group actually should have been called the NGC 4027 group, but I guess the more famous Antennae galaxies won ;-)

The high brightness of the galaxy means it should be visible in telescopes as small as 6", possibly smaller. However, the low declination might make it difficult to see for northern observers. I have only observed it with my 20" about a year ago. I logged my observation as follows:

"At 320x the galaxy is visible kind of as Pacman who's about to eat a star. The galaxy has a reasonably bright nucleus from which emerges an arm that completely detaches from the center. Between the center and the end of the arm lies a faint star. Very impressive!"

As always,

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

NGC 4027 is one of my favorite Arps. I observed it about 10 nights ago with my 4.7-inch f5 achromatic refractor, and even at low power it was readilyvisible at low power (along with the Antennae). I observe from 35 degrees north, I believe that under good conditions it might well be visible in small scopes even from 45 degrees north or even further north.

I did not make a sketch at the time, but it appeared as a roundish patch of light with a brighter center. I have observed it though several times with my 18", I will dig out my drawings within the next few days.

Nice OOTW Wouter. Here my result with the 16" telescope.

16", 257x, NELM 6m5+, Seeing II
Attachment 2026

I took these notes a few years back in Australia through a 24-inch f3.7 at 350x.

The main, bright northern component (NGC 4038) was partially annular, with a very bright knotty rim and a darker center giving a truly unique appearance for a galaxy. At least 3 knots were visible embedded along its rim. On the south side is the brightest knot which appeared faint, small, ~12" diameter. A second fainter knot is on the SW side and was only ~6" in size. Finally, a third very faint 6" knot is on the north side. The three knots were roughly spaced out 120° apart along the outer portion of this tortured galaxy. An elongated "arm" (the interacting companion NGC 4039) is attached on the east end and curves around on the south side towards the southwest. Another very faint, but slightly larger 20" knot is embedded along the main portion of NGC 4039, roughly halfway along its length. At the SW tip of the brighter portion of NGC 4039 was a relatively large, brighter knot that at times appeared double. Surrounding the SW portion of NGC 4039 is a much fainter outer halo extended SW-NE. This fainter halo extends beyond SW for a few arc minutes and widens to a bulbous shape at the end.

To my surprise I have have only one observation of NGC 4027 and it's from 1993:

"Whoops! I thought 4038/39 was it! This is fainter, vaguely elongated and rather irregular. Very faint star near the center with hints of other stars surrounding it. 182x, 20 inch f5."

On the other hand I have lots of observations of NGC 4038/39 so it's apparent I've let this more famous and detailed object steal my attention away from 4027. If the clear skies forecast for next week materialize perhaps I can get a good look at it then.

Hi folks,

just checked my observing notes of la palma, observed with 12":

"very nice object, with shape easy to catch: twisted - comparable to the shape of a fetus or just like a strongly curved waterdrop. The "tail" was aiming at a very faint star."

Could be that this "star" was the knot at the end of the arm (at 1 o´clock) - but i am not sure about that ´cause i got my sketch not handy right now. In worst case it was just the star at 3 o´clock ;-)

edit: Ahh - found my (quick ;-)) sketch in the internet from a former observing report - Arp 22 is to find in the middle. So the star is NOT the knot but indeed the star at 3 o´clock:

http://www.bilder-upload.eu/show.php...1399647117.jpg

CS!
Norman