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ASTRO: NGC 1637 a nice galaxy rarely seen for some reason



 
 
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Old May 12th 14, 09:17 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Default ASTRO: NGC 1637 a nice galaxy rarely seen for some reason

NGC 1637 is a rather nearby somewhat "sloshed" galaxy in northeastern
Eridanus. "Sloshed in the sense of asymmetric much as a raw egg becomes
sloshed back and forth in a fry pan with the yoke off center. I've seen
it called a three arm galaxy though to me it has only two arms that come
off a bar. The north one short going 180 degrees and not expanding all
that far from the core though it ends in an odd straight segment. The
other however makes a huge 360 degree arc passing over the much smaller
northern arm. Much of this arm is rather red in color indicating its
stars are rather old. How such an old arm without new star formation to
keep the density wave going that forms the arm can exist for so long is
a puzzle but one many red spirals have that are even older than this
galaxy.

Redshift puts the galaxy at 31 million light-years. Pretty close by my
standards. Redshift at such a close distance can be very misleading.
NED lists 21 non redshift measurements for it that have a median value
of 32 million light-years. Very close to the redshift value. Also
large telescopes can resolve its brighter stars indicating the distance
is likely correct. The bright region of the galaxy is about 24,000
light-years in diameter assuming the 31 million light-year distance.
Including the faint halo more than doubles its size to 55,000 light-years.

NGC 1637 was discovered by William Herschel on February 1, 1876 with a
18.7" reflector. It is one of the second Herschel 400 objects so made
my list for both being unusual and being on that listing of the second
400 in that AL observing program.

Seen faintly, the galaxy has a huge halo around it that is quite blue
and thus contains mostly very new stars. Most images of this galaxy
fail to pick up this as it requires a lot of exposure time, a lot more
than I gave it. I saw a hint of it when I started to process the image
but wasn't going to try and bring it out as it would be very noisy.
Then I remembered an article in the March, 2014 issue of Astronomy
Magazine (the American magazine not the English magazine of the same
name) by Adam Block explaining a Photoshop technique I'd not seen before
for bringing up such plumes without increasing noise significantly. It
is very quick and easy to apply. Nice to add a new trick to my bag of
processing tricks.

This is yet another field in an area little studied for its galaxies.
While there are a lot of background galaxies only 3 had any distance
data so the annotated image is rather sparse.

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

Rick
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Prefix is correct. Domain is arvig dot net

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