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Tuesday, May 11, 2021

In A Galaxy, Very, Very Far Away...

Just, beyond a galaxy - far, far away....lie, two other galaxies, in a galaxy group that, the three - have all to themselves. The little group is called the "Leo Triplet" but it is actually likely part of a larger group of galaxies called the "Leo-I" ('Leo One') group.

Moreover, like most things 'cosmological', the connections don't end there: gas-streamer bridges connecting one galaxy or group of galaxies to another group - ultimately, ending in "super-clusters"; i.e., a cluster of clusters of galaxies - the largest, single structures in the universe!

The proximity of the Leo Triplet puts it roughly between our own "Local Group" of galaxies and the Leo-I group; "galaxy-group neighbors", so to speak - or numerically: only, around 30-35mly (million light-years) distant. How far away is that? Well, about 300 times the diameter of the Milky Way galaxy, which is ~120kly (~120,000ly), across.

The "Leo Triplet" consisting of galaxies NGC 3628 (left), M65 (upper right), and M66 (lower right). Image provided by the author using Insight Observatory's 16" f/3.7 astrograph reflector, ATEO-1.
The "Leo Triplet" consisting of galaxies NGC 3628 (left), M65 (upper right), and M66 (lower right). Image provided by the author using Insight Observatory's 16" f/3.7 astrograph reflector, ATEO-1.
  
This tiny distant galaxy group features two spiral galaxies M-65 and M-66 discovered by French amateur astronomer Charles Messier; a comet-hunter by avocation. He tallied a list of small, dim objects in the night sky that appeared to be comets but he soon found we're not as they didn't move from their positions over long periods of time. They were permanent entities. He kept this list only to avoid these objects in future comet searches which he performed in the years around 1773.


The third galaxy, NGC-3628, another spiral saw edge-on; that is inclined 90° from our galactic perspective was discovered by German sister, and brother amateur astronomers William and Caroline Herschel back in the middle 1800s.

M-65, is a 'barless spiral, at 35mly. It is slightly warped, and, there has been some recent star birth activity in one of its gaseous H-II regions.

Of the three M-66 is closest at 31mly with a diameter of about 95kly. It is the brightest of the three but it is missing a large portion of one of its spiral arms. The missing mass from that arm was gravitationally removed by one or both of the other galaxies in the trio.

M-66, has a weak bar feature, extending from its core and in this way is reminiscent of our own barred-spiral galaxy, the Milky Way. As of 2018 five supernovae have been observed in M-66: SN-2016cok, 2009hd, 1997bs, SN-1989B, and 1973R. SN-1989B was discovered independently by amateur astronomers Mike Petrasko and Dale Alan Bryant - one, cold, still morning in Feb of that same year.

Lastly, NGC-3628, the edge-on galaxy in this trio is also known as the "hamburger" galaxy. (Yes - it does indeed look like a "quarter-pounder" - viewed from the side!) Its disk spans 90tly and sits at 35mly away. The galaxy is composed mostly of older stars and like the other two is easily visible in amateur-class telescopes (4+ inches of aperture diameter). NGC-3628 also sports a 300tly-long, 'tidal tail', connecting the other two galaxies. It is the most distant of the three at 35mly. Its disk is around 100tly across.

Since there has been so much supernovae activity within at least one of the galaxies in this trio, I've decided it would be a good idea to begin an extra-galactic supernova search program using these three 'island universes.

So, here's the plan: take images of the three galaxies all within a single frame at some periodic interval (time-series). Using an image of the three together that is known to be "supernova-free" - I can then compare subsequent images over time to the SN-free frame using a sort of 'blink comparator.

A blink-comparator is a device that was used frequently by astronomers to compare images of the same area of sky or objects within the same field-of-view of a telescope or camera over a specified interval. It involves the rapid sequencing back-and-forth of two images - one against the other. (In the distant, remote, ancient past - (*chuckle*: 1980's), I used two Kodak carousel slide projectors one stacked on the other projecting both slides at the same time onto a screen and then using a sheet of cardboard manually to alternately project the slide images one at a time in rapid succession onto the screen.

Currently, I'll use the two images in an animated, ".GIF", file, and "blink" them, that way. In this fashion, I can set the "blink" rate, interval, for optimal comparison. In this way, any deviation from the standard field (used as a sort of, 'control group'), such as blinking spot, line, or another anomaly, will stand out as extraneous data. This was how, Dr. Clyde W. Tombaugh, discovered the dwarf planet Pluto back in 1930. I'll be looking for any supernova activity within the three galaxies.

This is something that anyone using one of Insight Observatory's, remote telescopes can do on their own! It's a good way to involve oneself self in a Citizen Science project - of their own design!

I'll let you know if I find any action! -- you let me know what you find too!!

Dale Alan Bryant
Senior Contributing Science Writer

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