2 Attachment(s)
Object of the Week July 21, 2013 - NGC4656 The Hockey Stick
NGC 4656 The Hockey Stick
Canes Venatici
12 43 57.7
32 10 05
Type: SB(s)m Pec IV
Mag: 11.0 Size: 9.1’x1.7’
So keeping with the spirit of my beloved Chicago Blackhawks winning the 2013 Stanley Cup last month, I thought it would be fitting to choose this object as an OOTW. Not only is it a great object, but it actually does tend to resemble its moniker.
I’ve been observing NGC 4656 regularly for quite a few years now and each time I return, I would take for granted what my Megastar & Uranometria would depict. And that was NGC4656 and 4657 were two separate galaxies. The assumption is that 4657 is interacting with 4656 causing the gravitational distortion that was creating the “blade” of the hockey stick. But once I started my research for this OOTW, I stumbled onto something. (This BTW, is one of the reasons why working on an OOTW is so great. You learn so much!) I found that this may not be the case.
What I stumbled upon was a few internet sources that made the claim that the nearby Whale Galaxy NGC 4631(worthy of its own OOTW if you ask me) was the one distorting NGC 4656 and not 4657. Redshift measurements of the two galaxies do clearly show that the two are part of the same galaxy group. But in those same papers and sources, I found no reference to 4657 being an interacting object. I did find various websites making the assumption that 4656 and 4657 were interacting, but I found no credible evidence to prove it. So it got me to digging. Was NGC4657 a real galaxy or was it a misidentification? Even Hyperleda comes back with 4656 when you do a search for 4657.
A quick search with the folks at Harvard revealed a paper from 1983. One of the intentions as stated in the abstract was to determine whether or not 4656 and 4657 were part of the same galaxy. Apparently even back then there was doubt. Unfortunately though, they were not able to come up with conclusive evidence. They do suggest at the end of the paper that their "results favor a single galaxy model of a tidally distorted variant of a Magellanic type system.” I’m sure some more research savvy DSF members than myself can come up with some newer evidence to prove one way or another.
Visually, the galaxy is fantastic in all size scopes. There are reports online of 4656 pairing nicely with 4631 in 100mm telescopes. In my 25” the shape of the hockey stick stands out nicely with a very apparent widening at the handle. Along the core of the galaxy mottling is very clearly seen as well as what appears to be HII regions.
One thing I did notice looking at many images while researching this OOTW is a faint band of stars extending away from the blade. I’ve looked at the hockey stick plenty of times with the 48” but I’ve never made note of it. Then again, I never knew to look. Has anyone seen this extension? Is it even visble? You can make it out in the images below. Next time out, I’ll be sure to look for it.
Attachment 777 Attachment 778
Finally,
"Give it a go and let us know!
Good luck and great viewing!"
