A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Others » Astro Pictures
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

ARP 284 Reprocessed



 
 
Thread Tools Display Modes
  #1  
Old August 30th 17, 07:57 PM
WA0CKY WA0CKY is offline
Senior Member
 
First recorded activity by SpaceBanter: Feb 2008
Posts: 689
Default ARP 284 Reprocessed

I originally did this image in 2008. Recently I was asked if I had a version showing more glare from the bright star just south of the galaxies. I reprocessed it cleaning up a lot of the processing issues from my lack of tools back then. A few days ago I got two copies of Sky and Telescope's October 2017 magazine. That was because they ran my photo on page 64. It is too small to see much so am running it here to show the detail it missed. Also, while the article was all about a quasar in my image it doesn't mention all the other quasars in the image. They were too faint to see visually so weren't mentioned. They printed the image with south at the top while I post my images north at the top. Apparently to match the authors south at the top drawings.

ARP 284 is a pair of interacting galaxies NGC 7715 and NGC 7714 left to right. Arp classifies these under the heading of "infall and attraction" whatever that means. They are located a bit over 100 million light years away in the constellation of Pisces. NGC 7714 is a starburst galaxy. It has strong H alpha emission though I didn't take it in that light so it's not well seen in my shot. The starburst occurred some 3 to 9 million years ago. Note the odd reddish tidal arm at the lower right that just doesn't seem to fit the rest of the galaxy. The red color is due to mostly H alpha light so it is one huge area of ionized hydrogen. The companion NGC 7715 has H alpha emission and is not a starburst galaxy. It is classed as an irregular galaxy and is not an edge on spiral as it might appear. 7714 is an SB spiral that has been highly distorted by the interaction. Its core has emission lines that classify it as a LINER galaxy, a type with an active black hole in its nucleus.

The bright star at the upper right is also very interesting. It is SAO 128268 and is 126 light years away. What is interesting is that it is moving very rapidly through the sky. I was checking the POSS1 plates taken in the 50's at the Hale Observatory on Mt. Palomar when I noticed it wasn't in the same place as it is in my photo. Click this link http://stdatu.stsci.edu/cgi-bin/dss_...fov=NONE&v3 = to see that plate image. Note the two stars on either side of it are above it in that photo yet below it in my shot. It is moving upward and a bit to the east at a rate of about 1/3rd of a second of arc per year. In the approximately 50 years between the photos, the motion is quite obvious. Some stars show a high proper motion (movement through the sky) because they are close, Barnard's star is an example, while others do so because they really are moving fast. In this case, it is a little bit of both. NGC 7714 was discovered by John Herschel on September 18, 1830. It's not in either Herschel 400 program. NGC 7715 was discovered by Bindon Stoney on November 4, 1850. An HST image of NGC 1714 is at: http://cseligman.com/text/atlas/ngc7714hst.jpg but only shows a short piece of the arm that connects the two.

The star just below Arp 284 is one of the very few in all my images that is visible to the naked eye. It shines at magnitude 5.7 which means you can just barely see it on a dark moonless night from a location far from any lights. Averted vision (that is not looking right at it but somewhat to the side) will likely be necessary to see it. So it isn't an easy star to see but it can be seen. Unfortunately, that makes it so bright it made processing this image very difficult. Most of the scientific papers on the galaxy pair mention their measurements are likely tainted by the glare of the star so even the big boys are bothered by it. It is a spectroscopic double star about 100 light years away known as HD 221950 or 16 Psc. The latter indicates it is a naked eye star, the 16th in Right Ascension order in the constellation of Pisces. These numbers were assigned long ago so precession (a ~26,000 year wobble of the earth's axis) has changed the RA order of the stars in some cases but the original order numbers have been kept.

I've prepared a rather sparse annotated image that has little on the close galaxies but for those in ARP 284 but does show much more distant quasars and a galaxy cluster. Arp made a big deal about quasars around his active galaxies claiming the redshift of them had nothing to do with distance. By his logic, they weren't active massive black holes in distant galaxies but were something ejected from active galaxies. Redshift somehow related how long ago they were ejected. Higher redshift indicated they were ejected before those with lesser redshift. Somehow this involved electrons that changed with age. I've tried reading several of his books and other books trying to explain his logic and I end up a screaming basket case each time so may have this somewhat scrambled. With all the quasars around this actively interacting pair, he'd have had a field day though all have a rather similar redshift. I've not dug through his books to see if he mentions this one or not. My brain can't handle much more of his ideas.

Arp's image: http://ned.ipac.caltech.edu/level5/A...ig_arp284.jpeg

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

Rick
Attached Thumbnails
Click image for larger version

Name:	NGC7714L4X10RGB2X10X3R.JPG
Views:	669
Size:	211.2 KB
ID:	6667  Click image for larger version

Name:	NGC7714L4X10RGB2X10X3R-ID.JPG
Views:	384
Size:	222.4 KB
ID:	6668  Click image for larger version

Name:	NGC7714L4X10RGB2X10X3R-CROP125.JPG
Views:	233
Size:	83.9 KB
ID:	6669  
  #2  
Old August 31st 17, 11:23 PM
slilge slilge is offline
Senior Member
 
First recorded activity by SpaceBanter: Aug 2008
Posts: 151
Default

Rick,

that's a spectacular group. Great image.

Stefan
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Arp 157 reprocessed Rick Johnson[_2_] Astro Pictures 3 December 11th 10 08:13 PM
Sh-146 reprocessed Rick Johnson[_2_] Astro Pictures 3 August 22nd 10 01:39 AM
Arp 271 reprocessed Rick Johnson[_2_] Astro Pictures 2 September 3rd 09 12:25 AM
ARP 227 reprocessed Rick Johnson[_2_] Astro Pictures 3 July 8th 09 08:12 PM
Sh2-101 Reprocessed Dennis Persyk CCD Imaging 0 November 4th 04 02:24 AM


All times are GMT +1. The time now is 05:14 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.