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Wednesday, May 6, 2020

NGC 5907 - Galaxy with a Tail

NGC 5907, also known as Splinter or Knife Edge Galaxy, is a warped spiral galaxy about 150,000 light-years across and is located in the constellation Draco around 50 million light-years away from earth.

Back in 2019 after completing my project on M63 Sunflower galaxy, I decided to search for new objects to image using Insight Observatory's 16" f3.7 Dream astrograph reflector, ATEO-1, remote telescope. While I was surfing the internet, I came across an interesting galaxy. I made sure that it is visible in the northern hemisphere as ATEO-1 is located in the dark skies of New Mexico. I researched a bit more about this edge-on galaxy and found that tidal streams create a loop around this galaxy. I found a couple more images where there were two loops wrapped around the galaxy. I was really excited to capture this galaxy remotely as it was one of a kind and I could not find a similar galaxy that had two loops. I made a decision to capture this galaxy and I decided to email Michael Petrasko and Muir Evenden, Co-founders of Insight Observatory. As the tidal streams were very faint, it would mean investing a lot of imaging time. We started out and collected 5 hours worth of luminance data with ATEO-1.

NGC 5907, also known as the Splinter or Knife Edge Galaxy in the constellation Draco displaying its tidal loop and stream. Imaged on ATEO-1 with 29 hours of luminance image data combined with color image data from the Dragonfly Telephoto Array. Image data acquired by Muir Evenden and processed by Utkarsh Mishra and Michael Petrasko.
NGC 5907, also known as the Splinter or Knife Edge Galaxy in the constellation Draco displaying its tidal loop and stream. Imaged on ATEO-1 with 29 hours of luminance image data combined with color image data from the Dragonfly Telephoto Array. Image data acquired by Muir Evenden and processed by Utkarsh Mishra and Michael Petrasko.

After capturing 5 hours worth of image data from ATEO-1, I thought we could get some hint of the double loop but unfortunately, it wasn’t enough, although a wisp of the upper tidal stream was visible. I decided to research this a bit more and I found out that this stuff is very faint and probably needs 20-30 hours of exposure to reveal the kind of details I was looking for. Unfortunately, ATEO-1 was shut down for many months due to maintenance so I had to continue this project when it was back online. Michael reminded me about this project that was lagging behind so I decided to get back to work on it.

NGC 5907 imaged on ATEO-1 with 29 hours of luminance image data.  Image data acquired by Muir Evenden and processed by Utkarsh Mishra and Michael Petrasko.
NGC 5907 imaged on ATEO-1 with 29 hours of luminance image data.  Image data acquired by Muir Evenden and processed by Utkarsh Mishra and Michael Petrasko.

After a couple of days, I read an article from Sky and Telescope magazine that astronomers found that those double loops actually do not exist. My mind was completely blown and I shared this with Michael. This subject was getting more interesting day by day. I also came across a couple of images that showed that the loops do exist. I was really looking forward to working on this data and thanks to Michael and Muir, they managed to grab another 10 hours worth of data for me. I jumped on my computer to process it and I was expecting the double loop to pop up now but there was still no sign of it. I was unable to believe that even after 15 hours of exposure time with this really fast equipment under some of the darkest skies of the US, the double loop did not show up. I asked Michael to change the binning to 2x2, doubling the CCD camera's sensitivity. The data comprised of around 10 hours of bin 2x2 and 5 hours of bin 1x1. I then asked Michael if he could try imaging more data. The weather cooperated and we were able to gather 5 more hours of data. Once again, I looked on my screen with the expectation to see the double loop in my data, however, it looked like the image data was showing me something else. I processed the data and inverted it and found that the tidal streams were going downward and forming a structure similar to a tail.

I had many doubts regarding all the stuff that we captured so I quickly approached my friend Xavier Strottner. He has discovered many objects in space so I thought that he would have better knowledge and understanding of this. I had a great conversation with Xavier and he clarified all my doubts. He shared a few research papers with me so that I can read and understand more about this galaxy.

Inverted images of NGC 5907 imaged by the Dragonfly Telephoto Array (top) and ATEO-1 (bottom).
Inverted images of NGC 5907 imaged by the Dragonfly Telephoto Array (top) and ATEO-1 (bottom).

After working on 20 hours of luminance data, I started questioning whether the loops existed as they should have shown up.  I just had one more doubt that maybe we are not going for enough exposure length so I requested that Michael and Muir image 1200 sec sub exposers with binning 2x2 and erase all of my doubts regarding this double loop. Soon we were able to capture 4 hours worth of 1200 second image data and combine it with the rest of the data taken over the last year. I compared the 4 hours with the 5 hours we captured earlier in 2019. I could not find much of a difference in both. I requested Michael combine all data and make a master stack of it. After 24.5 hours of imaging time, there was still no sign of those double loops. However, I was very happy that we, amateurs, could capture the extremely faint tail that probably no one could do except the Dragonfly Telephoto Array. The Dragonfly telescope is an array of 48 lenses in two clusters of 24 and is equivalent of a 1.0 m diameter f/0.4 refractor. I also contacted a few astronomers working on these tidal streams to see if maybe they would publish a scientific paper on this in the future about our latest imaging on this data.

I would like to thank Michael, Muir and Xavier for providing excellent support throughout this project. I really enjoyed working together as a team. This project has really inspired me to image the entire tidal stream survey and I am looking forward to doing more such projects Insight Observatory using ATEO-1.

Personally, I also assume that "Team Insight" has only managed to capture the faint stellar tail in the amateur astrophotography world. 

Utkarsh Mishra
Lucknow, India

**All 29 hours of image data for NGC 5907 is available for download from Insight Observatory's image set repository "Starbase".

1 comment:

  1. It was amazing finding by you. I want to see like you only...keep growing.
    Congratulations to you & your team mate as well :)

    ReplyDelete