Object of the Week September 23, 2012 - Arp 273 A Galactic Trainwreck

[Dragan]

Arp 273

Interacting galaxy pair in Andromeda

RA 02 21 28.8
DEC 39 22 31

MAG: 13.4 (p) & 15.1(p) respectively

Lying at over 300 million light years away in the constellation Andromeda, Arp 273 is comprised of UGC 1810 & UGC 1813. Placed ideally in the sky as we enter our first week of astronomical autumn in the northern hemisphere, I thought this unique cosmic train-wreck would make a great OOTW this week.

I've had the pleasure to observe this object several times, the most recent being last October at our local dark site. Below are a few of my notes

29Oct 2011
25" f/5 "Toto"
Seeing 3/5
Transparency 4/5
NELM 6.1

Arp 273
Two faint glows observed at 242x (Ethos). By trying to place the bright star (now known to be 8th mag) outside the field of view at 393x & 450x (UO Orthos) UGC 1810 had what appeared to be 2 hazy arms/extensions. 1813 appeared as a uniformly bright elongated glow. Both had stellar cores.

Another night was under the much darker skies of the Nebraska Star Party. Dave Knisely was observing with me this night.

02Aug2011
25" f/5 Toto
Seeing 4/5
Transparency 4/5
SQM 21.85-90
393x & 450x (UO Orthos)

Arp 273. 2 rather obvious glows with some detail. UGC 1810 shows pretty defined arms that aren't too difficult to hold. 1810also had a rather obvious haze(?) around it. 1813 an elongated edge on shape with a stellar core. Possible connection between both galaxies that was thought to be seen using averted vision. Knisely confirmed.

Needless to say, my best view of Arp 273 was through Jimi's 48 on the night of 22oct09.

Through the 48" at 488x, both arms with of 1810 were visible using direct vision. Both arms showed a good deal of extension.


Here are a couple pics. A DSS shot as well as HST shot.

299298

So remember,

"GIVE IT A GO AND LET US KNOW"

GOOD LUCK AND GREAT VIEWING!

[Steve Gottlieb]

Great OOTW, Dragan! I missed the arms of UGC 1810 in my 18", but I certainly plan to take a look again soon in my 24". Of course, in Jimi's 48" the view was breathtaking.

By the way, that annoying bright star to the east is actually a striking double (STF 251), with the two components separating by 2.5"

[Uwe Glahn]

Hi Dragan,

"both arms with of 1810 were visible using direct vision" I have to say wow, that has to be a very spectacular view.

My experience with 16" were pretty the same as Steve wrote, I missed the arms but the glow let me hope a better view in in bigger telescope
16", 360x, NELM 7m+
301

Next try, bigger aperture. With 27" the arms were no problem at all. Although I missed the whole circle of UGC 1810, I could easily pick up the brighter arm segments.
27", 419x, NELM 7m+
302

[FaintFuzzies]

Great object! This reminds me to re-observe some of the Arps, which I missed detail on during my survey while gathering notes for my book. I'm actually running out of objects in my flat galaxy, galaxy trio and small galaxy group list...so this is a good time to tackle this project.

Anyhow here is my observation from a while back.

22" (305, 327, 458 and 575x) - A pair of faint galaxies near an mag 8.1 magnitude star. One, UGC 1810, is a very faint 2:1 elongated even surface brightness patch with a nearly stellar core. It is about 1' across and PA = 70. Its partner, UGC 1813, lies 1.4 SE and is a very faint 3:1 elongated even surface brightness patch. Very faint stellar core. PA = 90 and 45" long. No spiral structure seen at any magnification.