Bully galaxy rules the neighbourhood

[astroron]

Just in from ESO.
http://www.esa.int/esaSC/SEMNXV6K56G_index_0.html
View the main image in high resolution and see Globular Clusters from "Half a Billion Light Years Away":eyepop:

[pgc hunter]

bloody hell that's alot of globulars!

Any idea on the actual size of the galaxy?

[Jen]

:eyepop: wow nice image :thumbsup: so much to look at :)

[Kevnool]

Yes Jen you can practically swim in that image.
Thanks for posting Ron.
Cheers Kev.

[spearo]

Lots of galaxies in there
frank

[astroron]

Here is some info from Wiki.:thumbsup:
From Wikipedia, the free encyclopedia
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ESO 306-17
Observation data
Right ascension 05h 40m 06.67s
Declination -40° 50′ 11.4″
Redshift 0.035805
Type cD3
Apparent dimensions (V) 2.5 arcsec
Apparent magnitude (V) 13.33
Other designations
ESO 306-17 , ESO 306-G017 , ESO-LV 306-0170 , LEDA 17570 , AM 0538-405 , MCG-07-12-009
See also: Galaxy, List of galaxies

ESO 306-17 is a fossil group giant elliptical galaxy in the Columba constellation, about 1 million light-years in diameter, and half a billion light-years away.[1]

The galaxy is situated alone in a volume of space about it. It is theorized that the galaxy cannibalized its nearest companions, hence, being a fossil group.[2] The galaxy is a giant elliptical of type cD3 (E+3), one of the largest classes of galaxies.
[edit] References

[astroron]

Go into this site,
http://heritage.stsci.edu/2010/01/supplemental.html
Click on the side panels and you can add or subtract the Stars, back/foreground galaxies and globular Clusters,
You will be amazed just how many Globular Cluster there are.:eyepop:

[ngcles]

Hi Ron, PGC & All,

Thanks for posting that link Ron -- wonderful image of a true giant of the cosmos.



The approximate answer to this can be found resonably easily. According to the RC3* the vital statistics are:

ESO 306-17 = MCG -7-12-9 = PGC 17570 Galaxy *
RA: 05h 40m 06.6s Dec: -40° 50' 13"
Mag: 13.3 (P) S.B.: --- B-V: --- Size: 2.4'x1.4'
Class: E+3 P.A.: 177 Inclination: --- R.V.: +10734

The R/V (Recessional Velocity) of +10734 indirectly indicates a distance to be a tic under 493,000,000ly assuming the Hubble Constant (Ho) (H subscript zero) is 71km/sec/Mpc.

Once you have this approximate distance and the angular size on the sky you can get a good estimate on the diameter (d) usng:

d = 2 pi A D / 360

where

A = angular size of galaxy in degrees
D = distance to galaxy in light-years
d = diameter of galaxy in light years

Now, the size in the RC3* figures (above) is based on its apparent size on the survey plate down to a certain isophote level -- usually where the surface brightness of the eg drops below 25 magnitudes/arcsecond square. This new image is at least somewhat deeper than the survey plate, so it appears bigger than the image on the survey plate.

Using the new image and comparing it to certain landmarks on the plate viewed with Megastar and doing a bit of "clicking", I'd say a conservative angular size in our sky is something like 3.0 to 3.2 arcminutes -- not 2.4 arc-minutes as in the RC3* figures above.

So, plugging in a fairly conservative 3.0 arcminutes angular size on our celestial sphere and using the formula above gives ESO 306-17 an approximate diameter of 430,000-odd light-years. A less conservative (probably more realistic) 3.5 arc-minutes yields approximately 500,000 light-years diameter. -- that's your basic big-boy :thumbsup:.

What's more you should be able to see this in a 8"-10" 'scope from a good rural site without undue difficulty.

Compare that in size with Andromeda (estimates are now 220,000 to 250,000ly but lighter than the Milky Way because it's less dense) and the Milky Way at about 120,000ly.

But, you must remember that comparing spirals with ellipticals (this is an E+3) is a bit like comparing apples with lemons. As a guesstimate (we don't know the likely star-density or how much dark-matter there is), ESO 306-17 would be, maybe, 10 to 20 times more massive than the Milky Way -- possibly (somewhat) larger. Absolute bolometric magnitude for the whole eg around the (minus) -24.5 mark -- odd ...


Best,

Les D

[Ric]

That Hi-res image is just awesome.