Westerlund 2

[simmo]

Date: 22/02/14
Time: 7:30-10:30pm
Seeing: 8-9
Scope: sw 10" dobsonian
Eyepieces: 25, 12.5, 9, 6mm UO orthos (48x, 96x, 133x, 200x)

Object: Westerlund 2

Constellation: Carina
Mag: 10.5
Size: 2.0 arcmin

Notes: I found this object on Tuesday night and spent thurs as well as tonight studying it. On Tuesday what I thought to be an obscure object, that I probably wouldn't find, turned out to be actually quite interesting. It's a small cluster buried within the bright nebula NGC 3247. It is an elongated object much like the shape of an ice cream cone. :question: (Well to me at least anyway) it can be made out at low powers as a grey fuzzy however there is a little detail at 200x and it did seem that the centre of the object brightened. With averted vision it seemed that faint star or two could be just made out. Below I have included a drawing that I did tonight of roughly what could be seen at 200x through a 45 degree eyepiece.

What makes this object interesting is its stars contained within. This cluster contains some of the hottest, brightest and largest stars known. It has been fantastic reading. The X-ray photo below is from nasa but I think it was taken by Chandra which shows the cluster in detail.

Also there's some light reading included in regards to this cluster if your interested.

http://en.wikipedia.org/wiki/Westerlund_2

Thanks for reading
Simmo ;)

[simmo]

Here's the sketch from tonight. Not perfect but my first.

[Weltevreden SA]

Thanks much for your report & sketch, simmo. Wd 2 and its much fainter brother Wd1 (extinction a godawful 7 mags) are the two highest objects on my to-see list, and for the reasons you mentioned. They are exceptionally dense, young, and very hot, and are of great interest in the professional community. Arxiv and ADS list scads of papers over the last decade. I recall that the nebula and the cluster are unrelated, but will look into that now. Thanks again for the report on this rarely-chased cluster. All I need is the clouds to clear.

[simmo]

No worries Dana. Good luck with hunting it down. I had another look at it last night which seemed a little clearer than Saturday night and this time I could definitely see pinpoints of stars with averted vision. Would be interested to hear from you on whether the cluster and nebula are in fact related. Seeing the cluster is young you would surmise that there could be some star forming nebulosity close by. Unless of course due to its mass the cluster has absorbed most of the nebulosity that formed it.

Also I wondered if Westerlund 1 would be visible due to it being covered by the Milky Way. I couldn't find any observation reports anywhere from amateur astronomers, only professionals who had X-ray findings/data. My sky safari 4 plus has it listed only through the search function. There is no visual magnitude given and the data is a little vague. It rises quite late here at the moment, however, I like you Dana and others perhaps will be quite interested in investigating it in the following months.

[Paddy]

Hi Simmo,

Here are my notes on Westerlund 2 from April 2011 with 16" dob. I recall being quite fascinated by it, but didn't know about the interesting properties of its members. Don't seem to have any notes on Westerlund 1.

Thanks for the interesting read.

175X Westerlund 2 is a small bright thin line of resolvable stars packed very closely (this may be NGC 3247) NE-SW at the western end of the large irregular nebula RCW 49 with 20 easily resolved stars. The nebula is shaped like a rectangle topped by triangle pointing S, reminiscent of a child’s drawing of a house. Looks about 5’x7’. UHC filter darkens a segment of the northern edge of the nebula, the eastern section thickens and the triangle becomes dome shaped. “Alex Rodgers, Colin Campbell, and John Whiteoak, working at Australia's Mount Stromlo observatory under the direction of Dutch-American astronomer Bart Bok, published their nebula catalog in 1960. The RCW catalog is largely an expansion of Colin Gum's 1955 catalog.” From “the RCW catalogue” web site http://galaxymap.org/cgi-bin/rcw.py?s=1

[Weltevreden SA]

This post is a bit late out of the gate in the Wd 2 thread. I came across it in a 2004 APOD post (http://apod.nasa.gov/apod/ap040603.html) about the HI region surrounding Wd 2. The image clearly shows the line of about 5 stars that Simmo and Paddy reported. The RCW 49 nebulosity isn't nearly as visible at the eyepiece, but does reveal as a large extended patch when using a UHC filter. I checked it out last night under good skies and it shows as a miniature, faded version of the APOD image from Spitzer.

A bit of research has revealed Westerlund 2 to be one of the hottest and most interesting clusters in our skies. I'm about to post a new thread in three sections about it in the Astronomy & Science list.