Object of the Week February 22, 2015 - IC2574 Coddington's Nebula

[ChristianR]

IC2574 - Coddington's Nebula / Ursa Major (UMa)
Galaxy / Member of the M81 Group
RA: 10h 28m 23,48s Dec: +68° 24′ 43,7″
10,2 mag / Size: 13,2' x 5,4' (arcmin)

The dwarf galaxy IC2574 is located in the constellation Big Dipper and not far away from the magnificent pair M81 & M82.

Since IC2574 has a relatively low surface brightness, you've to accurately look when you're searching for it! I always start from M81 going first to NGC3077 located less than one degree east-south-east of it. 1,6 degrees east of NGC3077 you'll spot a 6th-magnitude star (accompanied by two 8th-mag stars).

Coddington's nebula is located just 45' east-south-east of this 6th-magnitude star and fits easily in the field of a low power eyepiece, just carefully peer for it.

The galaxy was discovered by Edwin Coddington in April 1898. Astronomers classify IC2574 as a dwarf irregular galaxy due to its relatively small size and lack of organization or structure. But note that you can find IC2574 classified as a "dwarf spiral galaxy" or "barred late-type galaxy" too. In other words, the classification is not really uniform.

However, the IC2574 is about 13 million light-years (LJ) away from us and a little less than 50000LJ in diameter. It shows clear evidence of intense star forming activity and this is what makes the dwarf galaxy interesting for a wide field of apertures.
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Image Credit and Copyright: Leonardo Orazi

Using my 12" dobson, IC2574 is an easy object using averted vision. It's even possible to identify the giant star forming area at the north end of the galaxy as outlined in the following sketch.
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Object: IC2574 - Coddington's Nebula
Type: Dwarf Galaxy (Uma)
Observing Place: Sudelfeld, Germany
Date, Time: March 13 2013, 11:50 pm
SQML = 21,5 mag/arcsec*2, seeing II-III, dry, 32 degF, relHum 50%
Dobson Hofheim Instruments 300mm / F5
Power: 75x (Nagler 20mm)

The following DSF thread from April 2013 collects a number of observations
http://www.deepskyforum.com/showthread.php?348-IC-2574-aka-Coddington-s-Nebula&highlight=ic2574

As already outlined, the galaxy is an interesting object for a really wide range of apertures. It even starts already with only a few inches on the one end - Sue French reports seeing it in a 105mm Apo Traveler - and there is as usual no limit at the other ...

Just to mention some of the highlights to be spotted:
- different star forming areas spread over the whole galaxy
- the separation from HII emission areas in the clusters
- the faint "tail" at the SW side

It's the right time now to look for this object.

"Give it a go and let us know”

[Ivan Maly]

Great target, Christian. The size is in minutes.

[ChristianR]

Thanks for the indication Ivan, I've corrected it.
Christian

[Uwe Glahn]

Hi Christian,

for sure worth a revisit with bigger aperture. I only knew the very interesting galaxy with 16". Thanks for the reminder.

16", 100x-257x, NELM 7m+, Seeing III
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[wvreeven]

I had a look at this galaxy with my 20" under SQM 21.5 skies. At 320x I saw a small oval patch of light. Then I lowered the power to 151x and a large, banana shaped glow appeared with a bright patch on one end. That, obviously, was the patch of light I saw at 320x. But this galaxy is large! And it is quite "fat" as bananas go :D Since I had a busy programme, I didn't look at it in more detail but I will another night.

[RolandosCY]

A very faint patch of light was detected under 21.0 skies using a 6" achro and a 13mm Ethos. As it was the beginning of the night and I felt I was not totally dark adapted, I made a mental note to return to it later, only for high clouds to cut the night short. Will give it a shot again soon though, using my 18"...

[reiner]

Great target, Christian!

I had it on my list already last week, but then forgot about it.

So I looked at it two nights before (my fifth observing night in this not yet ended new moon period :-) )

This is an unexpectedly large faint and diffuse dwarf galaxy. The one end with the star forming regions stand out immediately with my 22" already at 125x, while the other side tapers off diffusely.

With 9mm (280x) and 5mm (500x, a but too much), I tried to get more details out of the HII regions:

The regions at the northern end appeared clearly structured, but I was not able to pin them down individually. Most of the time, it appeared however as two separate clusters.

At the SE side, there is a line of three "stars", of which the middle one appeared clearly non-stellar (even that the seeing was not too good). From the image at hand, it was not evident, whether it was a star, but now at the computer, wikisky shows it as another HII region.

Roughly in the middle of the galaxy, I noticed at times some brighter spot, but was not able to pin this down precisely. It could have been one of the brighter spots in the core of the galaxy (or averted imagination :-) ).

A very good choice as OotW, as this is a nice and very overlooked target.