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IC 1101 largest galaxy - visible to us?

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#1 Fireball

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Posted 30 January 2010 - 12:05 PM

I just learnt that IC1101 is over 5 million lightyears wide.
That means, it is the largest galaxy we know so far. It seems to be 14,7m, which should be visible to larger dobsons.
Did anybody detect it visually ?
link: http://en.wikipedia.org/wiki/IC_1101

#2 GlennLeDrew

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Posted 30 January 2010 - 11:10 PM

I'm certain the listed diameter includes the vast, extended, *very* low surface brightness halo which most likely resulted from the one or more mergers of formerly separate galaxies. My impression is that this halo would be utterly invisible in *any* 'scope due to its faintness. And so I'd bet good money that the *visible* portion is but a *quite* small fraction diameter-wise. And as a result, a not insignificant fraction of the total light must be discounted when considering the integrated brightness of that smaller projected area. My guess might be a reduction of perhaps a full magnitude - 1/2 mag. at least.

As long as the 'core' subtends an angle of about 1/2 arcminute or more and its surface brightness is sufficiently high, it should indeed be visible in those dobs in the 'Big Bertha' category.

But take all this blather with a grain of salt. It's based entirely on what might best be called 'theory' and supposition - I've not seen this object myself!

#3 tatarjj

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Posted 31 January 2010 - 12:22 AM

You're pretty much right GlennLeDrew. IC 1101 MAY have a diameter of 6 million light years, according to some, but consider this:

1) IC 1101 sits at the center of a dense galaxy cluster
2) IC 1101 is the largest galaxy in the cluster
3) A vast halo of scattered stars exists throughout the cluster

Because IC 1101 is in the center of the cluster, is the largest galaxy in the cluster, and there is a vast swarm of stars orbitting throughout the cluster, the astronomers that announced that IC 1101 was 6 million light-years across were considering this vast swarm of stars. HOWEVER, there are litterally DOZENS of OTHER galaxies that orbit throughout the cluster, WITHIN this swarm of stars. So I think it is a little cheap and innaccurate to call IC 1101 6 million light years across. That swarm of stars could just as easily be called isolated stars that belong to no galaxy, orbitting the common center of the galaxy cluster. Keep in mind that IC 1101 has a quite clearly defined extent of only something like 170,000 light-years (can't remember what I calculated it to be exactly). The faint swarm of stars only was discovered in the like 80's with VERY long exposure images.

If you're going to call that shared swarm of stars that orbits throughout the cluster part of IC 1101, you might as well call the clearly defined separate galaxies that orbit within the swarm nothing but stellar associations and then call the entire cluster one big galaxy. Frankly, it's a little silly. IC 1101 is NOT 6 million LY across by a common sense definition.

Finally, consider how this vast swarm of stars formed. It was probably collisions by the OTHER galaxies in the cluster. In the collisions, some stars get stretched and pulled by tides and close encounters out of their host galaxies, and then just started orbitting the center of the cluster.

Still, IC 1101 of Abell 2029 is a BIG galaxy, and one of the easiest ways to get a relatively small telescope (like a 10", maybe even an 8") to see over a billion light-years without having to "cheat" by looking at quasars.

#4 sgottlieb

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Posted 31 January 2010 - 02:45 AM

... It seems to be 14,7m, which should be visible to larger dobsons.
Did anybody detect it visually ?


The simplest answer is YES! In fact, the galaxy was discovered visually well over 100 years ago (December, 1891) by Lewis Swift's 20-year old son Edward. He was using his father's 16-inch refractor at the Warner Observatory in Rochester, New York. The fact that it was swept up visually without prior knowledge by Edward implies it should certainly be visible in a smaller scope today knowing the precise location.

John brings up an interesting point -- excluding quasars and BL Lacertae objects, this object might be the most distant galaxy (1 billion l.y.) visible in a 10-inch or possibly smaller scope. Someone needs to take a look in a couple of months!

#5 desertstars

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Posted 31 January 2010 - 10:19 AM

Might not be the most impressive sight visually, but it would surely be a kick to have the largest known galaxy in you field of view. I'll have to give it a shot.

#6 HellsKitchen

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Posted 31 January 2010 - 05:45 PM

So IC1101 is actually 170,000 light years in size. Surely there are bigger galaxies then.

#7 Dave Mitsky

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Posted 31 January 2010 - 06:19 PM

The answer might differ depending upon the wavelength involved.

http://www.astronomy...spx?c=a&id=2188

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#8 telecasterguru

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Posted 01 February 2010 - 05:32 AM

I am going after it.

Frank

#9 HellsKitchen

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Posted 01 February 2010 - 07:06 AM

Interesting. Aren't the sizes of galaxies clear cut, I mean just measure the physical mass in visible light? So IC 1101 is really only 170,000 light years across then?

#10 PeterSurma

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Posted 01 February 2010 - 09:36 AM

IC 1101 is considered 'big' (in terms of mass, or number of stars) because its absolute magnitude is -23mag (m-M = 37.7mag, m=14.7mag), which is at the hi end of normal galaxies, brighter than -23mag normally means quasar or AGN.

Talking about size (i.e. diameter): it's hard to define 'diameters' for objects like elliptical galaxies (which have no clear cut boundary). As an escape people define such things as half-light radii, which means the radius which contains 50% of the total light of IC 1101. This value can be pretty large, yes, especially for diffuse objects with extended halos. In this respect/sense IC1101 could be a real monster... (I've not looked up the numbers though). Another definition (often used) could be the diameter of the surrounding line where the galaxy light line drops below SB=25mag/sq.arcsec... (CCD-measured) Only numbers that have been derived for the same defintion of radius can be compared, of course.

14.7mag can be seen in large dobs, of course. However, it won't be a fascinating view as such, because it's gonna be diffuse (large half-light radius, right ?). Just check the DSS image and compare it to other galaxies you may know ...

Yes this is definitely a dominating gx in a cluster, so it's gone through merging (i.e. canibalizing his environment) quite a lot, hence it's size + mass.

In fact, I do think it's interesting to have a look at this object and bear its size and mass in mind (e.g. relative to large galaxies in Virgo, cf. M87 has roughly M = -22 mag, i.e. a factor of roughly 2.5x less massive).

#11 Bret Ford

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Posted 01 February 2010 - 10:15 AM

John brings up an interesting point -- excluding quasars and BL Lacertae objects, this object might be the most distant galaxy (1 billion l.y.) visible in a 10-inch or possibly smaller scope. Someone needs to take a look in a couple of months!


IC 4064 in Canes Venatici goes even deeper--1.1 billion light years--and should be visible in similar instruments.

Class: Lenticular
R.A.: 13h01m06.8s
Dec.: +39°50'29"
Magnitude: 14.50 B
Size: 1.4'x 1.1'
Mean Surface Br. 23.2 Mag/arcsec^2
V®: 25496.0 km/sec
Redshift (z): 0.08
(Data from SkyTools 3)

Bret

#12 Ptarmigan

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Posted 01 February 2010 - 01:02 PM

To put it this way, if IC 1101 was 33 light years or 10 parsecs, it would be quite bright. Absolute magnitude is measured if the object was 10 parsecs away. Some quasars have really bright absolute magnitude, as bright as -32. The Sun has an absolute magnitude of 4, which would be a background star in the sky. Think about a world where it is near a bright galaxy or quasar. Perpetual daylight, first from the star that the planet orbits, than a galaxy or quasar at night. I don't think I would like that.

#13 tatarjj

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Posted 01 February 2010 - 03:23 PM

Ok, I was wrong about the 170,000 light year estimate- it was a number I pulled off the top of my head from memory- see my original post where I said: "something like 170,000 light-years, I don't remember what I calculated exactly".

The galaxies actual visible angular extent is something around 1.5'- at a distance of 1 billion light years, that corresponds to roughly 440,000 light-years.

See this image of IC 1101 below. This is from the SIMBAD astronomical database, http://simbad.u-strasbg.fr/simbad/. I have marked the angular size of 300,000 light years at 1 billion light years as a reference. As you can see, if the people claiming that IC 1101 is 5 or 6 million light-years across are correct, then the galaxy fills the ENTIRE image field of view, and MORE. In fact, it would be 19' across, or about 2/3rds the size of the full moon. It would also include all those galaxies WITHIN itself. Really, if it was truely 5-6 million light years across, you should consider the entire galaxy cluster Abell 2029 one galaxy.

This seems absolutely ridiculous to me. We have detected unbounded stars within the Virgo cluster, and we don't consider THAT one giant galaxy. I'd think that the standard defnintion of a galaxy would put this galaxy's boundries at only about 400,000 light-years. Still HUGE though.

Attached Thumbnails

  • 3597990-IC 1101.jpg


#14 sgottlieb

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Posted 01 February 2010 - 09:47 PM

IC 4064 in Canes Venatici goes even deeper--1.1 billion light years--and should be visible in similar instruments.

Class: Lenticular
R.A.: 13h01m06.8s
Dec.: +39°50'29"
Magnitude: 14.50 B
Size: 1.4'x 1.1'
Mean Surface Br. 23.2 Mag/arcsec^2
V®: 25496.0 km/sec
Redshift (z): 0.08
(Data from SkyTools 3)

Bret


I'm not sure of the source for the SkyTools data, but NED gives a redshift for IC 4064 of less than half that amount (z = .0356). All of the data is NED is documented with the source material. See http://tinyurl.com/y8dh63y

#15 Bret Ford

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Posted 01 February 2010 - 10:11 PM


IC 4064 in Canes Venatici goes even deeper--1.1 billion light years--and should be visible in similar instruments.

Class: Lenticular
R.A.: 13h01m06.8s
Dec.: +39°50'29"
Magnitude: 14.50 B
Size: 1.4'x 1.1'
Mean Surface Br. 23.2 Mag/arcsec^2
V®: 25496.0 km/sec
Redshift (z): 0.08
(Data from SkyTools 3)

Bret


I'm not sure of the source for the SkyTools data, but NED gives a redshift for IC 4064 of less than half that amount (z = .0356). All of the data is NED is documented with the source material. See http://tinyurl.com/y8dh63y


Thanks for that update. I'll send Greg a note--he applies changes to the database when he updates the program.

Bret

#16 Fireball

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Posted 03 February 2010 - 03:15 AM

Interesting discussion!
When I posted my question I doubted that a "classical shaped" galaxy (spiral or elliptical) can ever reach a width of several million light years. If yes, that really would be a new class of "big bodies" :bigshock:

#17 Feidb

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Posted 03 December 2014 - 11:54 PM

It's a pretty tiny little oval, to boot!



#18 sgottlieb

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Posted 04 December 2014 - 12:43 AM

Since this thread has been brought back to life, I'll mention an observation I made in my 18-inch f/4.3 Starmaster back in 2011 at the Golden State Star Party.

 

18" (6/30/11): this supergiant cD galaxy is the dominant member of AGC 2029 (z = .078 at 1 billion light years!)  At 280x, it appeared very faint, very small, slightly elongated ~N-S, ~15"x10".  Visible continuously with averted vision.  The galaxy is squeezed between a mag 14.7 star 27" E and a mag 15-15.5 star 47" WNW, just slightly south of a line connecting the two stars.  No other members of the cluster were seen.  I also viewed it at a similar magnification in Alan Agrawal's 24" f/3.3 and logged "faint, very small, round, oval 3:2 N-S, ~20"x14".  Could just hold steadily with direct vision."



#19 Alan A.

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Posted 05 December 2014 - 03:35 AM

 Hi Steve,

 

I remember quite clearly the night we viewed IC1101.  Knowing its massive size and great distance, it was very exciting to see it, and it's on my list now of favorite objects.  I was quite impressed that we could see it with direct vision without much difficulty in the 24", thanks for  suggesting we look at it.

 

Alan



#20 nytecam

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Posted 08 December 2014 - 05:36 PM

Just the core of N1101 + nearby faint fuzz of foreground gxys from summer 2013 below :waytogo:

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  • ic1101sgx130730x5mg.jpg


#21 penguinx64

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Posted 10 December 2014 - 06:00 PM

I just learnt that IC1101 is over 5 million lightyears wide.
That means, it is the largest galaxy we know so far. It seems to be 14,7m, which should be visible to larger dobsons.
Did anybody detect it visually ?
link: http://en.wikipedia.org/wiki/IC_1101

 

With an apparent magnitude less than 10, I'll never see it in my scope.



#22 quazy4quasars

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Posted 24 December 2014 - 03:18 PM

Having seen it-

 

  I can say that it is very big, for a galaxy at a billion ly - no doubt some of that due to the combined glow of the various close ellipticals about----

It was not difficult in 25" at all, more due to it's size than to its brightness, however there was pronounced lumpiness to its luminosity profile.

 

  Total magnitude est-14.0,  possible to spot at low powers within a large trapezoid of 10-11 mag stars  just 2 degrees almost due north (NNNW)

of the mighty M5.  Any 8" or larger scope could glimpse it as a FLN (Fuzzy Little Nothing)  under very dark skies    




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