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ASTRO: UGC 2885 Largest Spiral in the Universe -- Maybe



 
 
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  #1  
Old January 22nd 12, 04:45 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
external usenet poster
 
Posts: 3,085
Default ASTRO: UGC 2885 Largest Spiral in the Universe -- Maybe

UGC 2885 is a huge spiral classed as SA(rs)c. That much is obvious.
After that things get murky. First link at Google says it is the
largest known spiral at over 800 thousand light-years (250 kpc)! Yikes.
I found this repeated several places. But as I dug deeper things
became rather confused. NED shows a redshift of 5800 kms. Same as the
site saying 800 thousand light-years gives. That puts it about 260
million light-years distant. They give its diameter as 5.5 minutes.
Doing the math that gives a size 416 thousand light-years! Their own
figures don't work.
http://weblore.com/richard/ugc_2885.htm

Another site (http://adsabs.harvard.edu/full/1985A%26A...146..213R) says
the distance is 118 Mpc (384 million light-years) but this uses an old
now disproved Hubble constant. Using this inflated distance they put it
at 80 kpc (260 thousand light-years) radius or 520 thousand in diameter.
Adjust this for the currently accepted distance of 260 million
light-years and the size is 350 thousand light-years. We seem to have
the incredible shrinking galaxy here. This agrees with my size estimate
of 4.8' using the longest radius in my image when stretched far more
than in the attached image. In kpc the diameter is about 110 kpc. Very
large but not the humungous galaxy often quoted. In any case it is
still a monster spiral. Is it the largest known? That I can't say. It
is as large or larger than any I know of. Some ellipticals are larger
however.

The field is heavily obscured, at least 1 magnitude. So is it larger
than we can see because of this? I checked radio and IR references.
Radio and IR see it about the same as my image so while obscured we are
seeing the majority of the galaxy.

These sites also make claims the galaxy has rotated 12, 10, 8 and 5
times (various papers I found). These assume the galaxy has been around
since the beginning of the universe. Some of the difference in
estimates has to do with the accepted value for Hubble time at the date
of the paper's publication but it can't begin to explain the wide
variation given. To compare our sun, if it and our galaxy had existed
for the 13.7 billion years of the universe. It would have rotated over
60 times.

This galaxy is also trotted out by supporters of MOND an alternate
gravity theory used to deny dark energy. How much their argument relies
on the over estimate of its size I don't know. But all start out
touting its super large size so I suspect it is important to their
argument. I have to admit I got lost in their papers so this might be
an incorrect assumption.

The weirdness doesn't stop there. For some unexplained reason NED has
the wrong coordinates for this galaxy. A case of close but no cigar.
There is a very bright orange star at the northeast end of the densest
part of its disk. Between it and the actual core are two fainer stars.
the lower bluer. This one is at the exact position NED shows for the
galaxy! At the position of the core they show [WGB2006] 034948+35270_a
with no size or magnitude data. Other than the size being slightly
small for their misplaced UGC 2885 everything else seems reasonable.
Likely they interchanged these two objects. So is that blue star really
a galaxy? I doubt it. The PSF matches similarly bright stars. A minor
error but considering what I'd already found it rather surprised me that
the errors continue.

Off the southwest end of the galaxy is LEDA 213253/2MASX
J03525142+3534301 an IR rich galaxy. It shares a similar redshift value
to UGC 2885 so is likely related. While there are 12 other identified
galaxies in my field at NED all from the 2MASS IR catalog, none with
much information so I didn't bother with an annotated image.

Some of the dust that obscures the galaxy is seen as a slight blueish
glow on the right side of the image. On the right edge is a reddish
streak coming in to a small galaxy. This caused by a star off the frame
hitting something in the camera and reflecting in to the field. A blue
star does the same from the top edge of my image.

The asteroid at the bottom of my image well left of center is (27704)
1984 WB4 at magnitude 16.7. The green frame was taken after it moved
out of the field.

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

Attached Thumbnails
Click image for larger version

Name:	UGC2885L4X10RGB2X10X3.JPG
Views:	415
Size:	321.8 KB
ID:	3918  Click image for larger version

Name:	UGC2885L4X10RGB2X10X3CROP.JPG
Views:	128
Size:	130.4 KB
ID:	3919  
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  #2  
Old February 6th 12, 08:34 PM posted to alt.binaries.pictures.astro
Stefan Lilge
external usenet poster
 
Posts: 2,269
Default ASTRO: UGC 2885 Largest Spiral in the Universe -- Maybe

Rick,

a most interesting "story" to go with the image. Never heard of this object
before.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
om...
UGC 2885 is a huge spiral classed as SA(rs)c. That much is obvious.
After that things get murky. First link at Google says it is the
largest known spiral at over 800 thousand light-years (250 kpc)! Yikes.
I found this repeated several places. But as I dug deeper things
became rather confused. NED shows a redshift of 5800 kms. Same as the
site saying 800 thousand light-years gives. That puts it about 260
million light-years distant. They give its diameter as 5.5 minutes.
Doing the math that gives a size 416 thousand light-years! Their own
figures don't work.
http://weblore.com/richard/ugc_2885.htm

Another site (http://adsabs.harvard.edu/full/1985A%26A...146..213R) says
the distance is 118 Mpc (384 million light-years) but this uses an old
now disproved Hubble constant. Using this inflated distance they put it
at 80 kpc (260 thousand light-years) radius or 520 thousand in diameter.
Adjust this for the currently accepted distance of 260 million
light-years and the size is 350 thousand light-years. We seem to have
the incredible shrinking galaxy here. This agrees with my size estimate
of 4.8' using the longest radius in my image when stretched far more
than in the attached image. In kpc the diameter is about 110 kpc. Very
large but not the humungous galaxy often quoted. In any case it is
still a monster spiral. Is it the largest known? That I can't say. It
is as large or larger than any I know of. Some ellipticals are larger
however.

The field is heavily obscured, at least 1 magnitude. So is it larger
than we can see because of this? I checked radio and IR references.
Radio and IR see it about the same as my image so while obscured we are
seeing the majority of the galaxy.

These sites also make claims the galaxy has rotated 12, 10, 8 and 5
times (various papers I found). These assume the galaxy has been around
since the beginning of the universe. Some of the difference in
estimates has to do with the accepted value for Hubble time at the date
of the paper's publication but it can't begin to explain the wide
variation given. To compare our sun, if it and our galaxy had existed
for the 13.7 billion years of the universe. It would have rotated over
60 times.

This galaxy is also trotted out by supporters of MOND an alternate
gravity theory used to deny dark energy. How much their argument relies
on the over estimate of its size I don't know. But all start out
touting its super large size so I suspect it is important to their
argument. I have to admit I got lost in their papers so this might be
an incorrect assumption.

The weirdness doesn't stop there. For some unexplained reason NED has
the wrong coordinates for this galaxy. A case of close but no cigar.
There is a very bright orange star at the northeast end of the densest
part of its disk. Between it and the actual core are two fainer stars.
the lower bluer. This one is at the exact position NED shows for the
galaxy! At the position of the core they show [WGB2006] 034948+35270_a
with no size or magnitude data. Other than the size being slightly
small for their misplaced UGC 2885 everything else seems reasonable.
Likely they interchanged these two objects. So is that blue star really
a galaxy? I doubt it. The PSF matches similarly bright stars. A minor
error but considering what I'd already found it rather surprised me that
the errors continue.

Off the southwest end of the galaxy is LEDA 213253/2MASX
J03525142+3534301 an IR rich galaxy. It shares a similar redshift value
to UGC 2885 so is likely related. While there are 12 other identified
galaxies in my field at NED all from the 2MASS IR catalog, none with
much information so I didn't bother with an annotated image.

Some of the dust that obscures the galaxy is seen as a slight blueish
glow on the right side of the image. On the right edge is a reddish
streak coming in to a small galaxy. This caused by a star off the frame
hitting something in the camera and reflecting in to the field. A blue
star does the same from the top edge of my image.

The asteroid at the bottom of my image well left of center is (27704)
1984 WB4 at magnitude 16.7. The green frame was taken after it moved
out of the field.

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net



 




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