APOD and General Astronomy Discussion Forum
https://asterisk.apod.com/
markh@tds.net wrote: ↑Wed Nov 13, 2019 2:13 pm Abell 2151 Galaxy Cluster
Copyright Mark Hanson
Abell2151SmallA.jpg
Description by Sakib Rasool
Abell 2151 is a mighty cluster of galaxies with a surplus of beautiful interacting galaxies. Interestingly its distribution is quite chaotic and lacks the typical central elliptical galaxy that is a common feature of most galaxy clusters. However the brightest galaxy is the elliptical NGC 6041.
In the grand scheme of the universe, Abell 2151 (also known as the Hercules Galaxy Cluster) is located 500 million light years away and covers an area of 6 million light years with about 200 galaxies. It is part of the Hercules Supercluster, which is part of an even larger extragalactic structure simply known as the Great Wall. This has a huge span of 500 million light years and was discovered in the 1980's by Margaret Geller and John Huchra.
One aspect of Abell 2151 that is immediately apparent is the abundance of peculiar and interacting galaxies. In fact, there are so many that a record number of four were included in the Arp Atlas, the most for any galaxy cluster. These include Arp 71 (NGC 6045), Arp 122 (NGC 6040), Arp 172 (IC 1178/81) and Arp 272 (NGC 6050/IC 1179).
NGC 6040 is an interesting pair of galaxies interacting with each other and in the process of being absorbed into the galaxy cluster, its neutral hydrogen gas has been removed through ram pressure stripping, a phenomenon that has been observed in other galaxy clusters. NGC 6050 and IC 1179 represent a titanic collision between two behemoths that have been observed with the Hubble Space Telescope, which appears to show a third member in this system.
Arguably the most distinguished member of Abell 2151 is IC 1182, a strange chaotic wreck of a galaxy that was somehow overlooked by Halton Arp. Although it is tempting to perceive the elongated blue structure as a jet launched from its core, it is in fact a tidal tail with a weaker second one near the opposing side. Another famous example of tidal tails being misconstrued as jets are the ones associated with the southern galaxy NGC 1097. In IC 1182, the longer tidal tail has a length of 205,000 light years while the smaller one is 88,000 light years long. It is very llkely its unique morphology is the result of an ongoing merger between two galaxies. Another interesting conclusion drawn from professional studies is that some of the blue knots in the large tidal tail might be in the process of forming tidal dwarf galaxies!
Make sure to take a look at the full resolution image here: https://www.hansonastronomy.com/abell2151
Thank you,
Mark Hanson
I'm usually not a great fan of planetary nebulas, mostly because I can't figure out what their "true color" is, and different pictures of the same planetaries show different colors in them, so I give up.markh@tds.net wrote: ↑Wed Nov 13, 2019 2:18 pm Abell 78
Copyright Mark Hanson
Abell78-4small.jpg
Abell78-4CropA.jpg
Called Abell 78, it can be found a few thousand light-years from Earth toward the constellation of Cygnus. In its heyday, it wasn’t all that different from the Sun, only the key difference is, the Sun remains a main-sequence star. Whereas, Abell 78 is dead… it no longer fuses hydrogen into helium—it is now classified as a planetary nebula.
Unlike other nebulae of its kind, Abell 78 belongs to a rare subclass called, you guessed it, born-again planetary nebulae. They have the same nuts and bolts as normal ones. Most important is the white dwarf: the small, but dense, object situated directly in the heart of the nebula. In this instance, the gas surrounding the central star becomes so tightly-packed in certain areas, nuclear fusion starts back up.
“The renewed nuclear activity triggered another, much faster wind, blowing more material away. The interplay between old and new outflows has shaped the cloud’s complex structure, including the radial filaments that can be seen streaming from the collapsing star at the center.”
Telescope: Planewave 24" f6.7 on a Planewave HD Mount Camera: SBIG 16803
Taken at Stellar Winds Observatory, a/k/a Stan Watson Observatory in Animas, NM.
Full Resolution Image can be found here: https://www.hansonastronomy.com/abell-78
Thank you,
Mark Hanson
Welcome, Peter! You appear to be new here. I particularly like your beautiful pink and blue version of the Heart Nebula. I also really like your picture of M63, which clearly shows the large, almost colorless halo surrounding this galaxy.pepe30 wrote: ↑Wed Nov 13, 2019 6:22 pm Hi,
I attach my attempt to IC 1805 in the Hubble palette
I attach my attempt to IC 1805 in BICOLOR palette (Ha,OIII)
http://astrobook.sk/profile/21/posts/
Peter (pepe30)
That's a great image and a fantastic opportunity to really compare the two galaxies! I so appreciate that we can see all of LMC, because the outer parts of it are often cut off. SMC also seems to show off all its parts in all their glory!litobrit wrote: ↑Fri Nov 15, 2019 5:29 am Hello,
The two Magellanic Clouds in a single image.
4 Tiles and 15 hours LRGBHaOIII with a Nikon 200 and a ASA20 from Chilescope.
Acquisition Jean-Baptiste Auroux https://millenniumphoton.com and Bernard Michaud https://www.astrobin.com/users/litobrit/
Processing Bernard Michaud.
The full is here https://www.astrobin.com/full/phig1x/B/?nc=user
But I really wanted to see if I could catch this beautiful Supernova remnant, and I'm glad it succeeded 
I'm not the right person to comment on your image, Andre, since neither bicolor images nor supernova remnants are really my forte. But I am so impressed that you spent so much time on a single object to make the very most of it. I really applaud you!avdhoeven wrote: ↑Sat Nov 16, 2019 2:58 pm Here is the continuation of my large summer-2018 project.
Little Veil Nebula by Andre van der Hoeven, on Flickr
I had imaged this region for about 13 nights altogether between July and October 2018. You can call me crazy, using so many nights for just one object, in a region where clear nights are rare
The overview image shows the constellation of Cygnus and shows where the remnant is found. It's often also called the 'Little Veil Nebula' although it's quite a bit larger in the sky than it's name-share the Veil nebula (seen on the lower left).
Recently Pixinsight was supplied with the new Starnet++ module, which you can use to completely separate the stars from the background. I used this software to enhance the very weak nebulosity and was astonished to see how much more could be drawn from the background compared to the processing I did last year. All other processing was performed using Astropixelprocessor and photoshop.
Supernova remnants (SNR) are formed when a large star ends its life in a supernova explosion. About 300 of these remnants are currently known in our galaxy. One of the most famous remnants, the Veil Nebula, is located in the constellation of Cygnus. Although this is the most famous one in this constellation, it’s not the only SNR. Cygnus contains several obscure SNR’s, among which SNR 65.3+5.7 (also known as SNR 65.2+5.7).
SNR G65.3+5.7 was discovered by Gull et al. (1977) during an OIII survey of the Milky Way. Some parts of this SNR were already catalogued by Stewart Sharpless in his SH2 catalog as SH2-91, SH2-94 and SH2-96, but they were not recognized as being part of a bigger structure at that time. The idea that they could be part of a larger SNR was postulated by Sidney van den Bergh in 1960, but it took until 1977 for this to be confirmed.
This is one of the larger SNR in the sky spanning a region of roughly 4.0x3.3 degrees. Mavromatakis et al. (2002) determined the age of the SNR to be 20.000-25.000 years and the distance about 2.600 – 3.200 lightyears. The shell has a diameter of roughly 230 lightyears! This SNR is a predominantly OIII shell with also some H-alpha signal.
This supernova shell is quite weak and there are hardly any high-resolution images of this region. In the internet maybe 5-10 deep images of this shell can be found and, in most cases, they don’t cover the entire shell or the resolution is quite low because it was done by using photo lenses at short focal lengths. That’s why I decided to see if I could try to image the entire shell using my equipment, a TMB92 refractor in combination with a QSI583ws ccd camera. Because of its large size I needed to make a 3x3 mosaic to cover the whole region.
As so many nights were already necessary to cover the region in OIII I didn’t succeed in grabbing the H-alpha data, but on the internet I found the MDWsurvey (mdwskysurvey.org) initiated by David Mittelman (†), Dennis di Cicco, and Sean Walker (MDW). This is a marvelous project with the goal to image the entire northern sky in H-alpha at a resolution of 3.17”/pixel. I contacted them and told them of my effort to grab imagery of this SNR and they were very kind to provide me with the H-alpha imagery of this region, so that the entire SNR could be brought into view in reasonable high resolution.
This bicolor image shows a combination of about 53h of OIII data (made by myself) and 20 hours of Ha-data (made by the MDW survey) in a single image. In this way the full span of the shell can be seen in all its glory.
Image info:
H-alpha (astrodon 3nm, mdwskysurvey.org):
Telescope: Astro-physics AP130mm starfire
Camera: Fli Proline 16803
5 frames of 12x1200s each
OIII (astrodon 3nm):
Telescope: TMB92SS
Camera: QSI583ws
9 frames, 158 x 1200s total
Where is the overview image? I can't find it.The overview image shows the constellation of Cygnus and shows where the remnant is found.
