https://www.universetoday.com/wp-content/uploads/2009/05/Local_Group_and_nearest_galaxies.jpg
This is a depiction of what Astronomer Edwin Hubble called the “Local Group” of galaxies, mostly within 8 million light-years of our Milky Way. While it appears that all of the nearby galaxies are clustered in one quadrant, that may not be the case. Our Solar System is located on a spur of an outer arm of the Milky Way spiral as you can see below, and looking across the extremely bright and dense central bulge of our own galaxy is nearly impossible. We can’t see what is being blocked by that intense light and the millions of stars and glowing dust in that direction, and may never know what is there.
NGC891 - Silver Sliver - an edge-on unbarred spiral galaxy with Wide Field Numerous Galaxies. This galaxy is roughly 30 million light years away. What I love about this picture is that you can zoom in to almost any part of it and see more galaxies, especially in the bottom right quadrant. This is the part of the local supercluster os galaxies, which includes our Milky Way. Throughout the universe, we've found that galaxies tend to cluster in regions, with gaps between, and we are in this local group. Anything in this picture that isn't a point source of light, or has a haze around it, is most likely a galaxy. I gathered this data while visiting my son in semi-rural northern Illinois over a few nights, with 368 images of 3 minutes exposure each, using H-Alpha, S-II, and O-III filters on a William Optics FLT-120 with a focal length of 780mm. I used an ASI 2600 Pro monochrome camera with a 6248x4176 pixel array and giving 0.9943 arcsec/pixel resolution, a ZWO AM5 mount, and ASIAir Plus running the ASIAir app. Processed with PixInSight and Adobe Photoshop
NGC1398 is a Double Ring Barred Spiral Galaxy. The name is pretty generic - the intense center of the galaxy has a “bar” across it, surrounded by a ring, surrounded by other rings. I have yet to find any explanation for the source of the “bar”. NGC1398 is 64.5 million light years away, so the light we are seeing right now actually left that galaxy shortly after the dinosaurs were destroyed by the mountain-sized asteroid that slammed into the earth near the Yucatan Peninsula. This galaxy has a diameter of about 135,000 light years, which makes it slightly larger than our Milky Way Galaxy. This was the first image I compiled using LRGB+H-Alpha data, collected from what Telescope.Live calls “CHI-1”, a Planewave CDK24 610mm diameter, 3962mm focal length telescope with Corrected Dall Kirkham optical design, situated in the Rio Hurtado Valley, Chile. LRGB is Luminance, Red, Green, and Blue filters, and a Hydrogen-Alpha filter, and processing that type of data uses a slightly different technique than used with SHO - Sulfur-II, Hydrogen-Alpha, and Oxygen-III filters. SHO filters are all very narrow band, usually +/- 3 to 5 nm from the central wavelength of that element. RGB filters are wideband, each capturing a larger portion of the color spectrum, and all done with very large format monochrome sensor cameras. This image was combined from 36 x 300s Luminance, 37 x 300s Red, 37 x 300s Green, 39 x 300s Blue, and 60 x 300s H-Alpha images, for a total of 17.5 hours total exposure time. The camera is a QHY 600M Pro with a Sony IMX455 sensor, 30.6MP and 0.39 arcsec/pixel in BIN2. Processed with PixInSight and Adobe Photoshop
M81 Bode's Galaxy, a Grand Spiral Galaxy (lower), and M82, The Cigar Galaxy with a Supermassive Black Hole (upper right). I finally collected enough data (363 3-minute exposures) to process this pair, 12 million light years from my back yard outside Memphis, TN in Bortle 5 skies. M82 is roughly half the diameter of our Milky Way, yet overall is 5 times more luminous, and the central region is 100 times more luminous. The red jets shooting out of the center are mostly hydrogen, and hypothetically caused by frequent supernova in the intense star-forming regions around the core of M82. In addition to a supermassive black hole in the core, measured as approximately 30 million times the mass of our sun, it also seems to have an intermediate-mass black hole somewhere between 200 to 5000 times the mass of our sun, located about 600 light years from the center. M82 also contains the first Magnetar (https://en.wikipedia.org/wiki/Magnetar) detected outside our own galaxy. As usual, I ran H-Alpha, S-II, and O-III filters on a William Optics FLT-120 with a focal length of 780mm. I used an ASI 2600 Pro monochrome camera with a 6248x4176 pixel array and giving 0.9943 arcsec/pixel resolution, a ZWO AM5 mount, and ASIAir Plus running the ASIAir app. Processed with PixInSight and Adobe Photoshop
IC342, The Hidden Galaxy, obscured by the dust of our own Galactic Core
M31 Andromeda Galaxy - Andromeda is the largest nearby galaxy (only 2.5 million light years away, or 1.47 x 10^19 miles or 14.7 billion billion miles), visible to the naked eye in dark skies. There are many closer galaxies as you can see in the depictions above, but none are as easily observable as Andromeda. While size and mass estimates have fluctuated significantly over the last couple of decades, scientists now think it is approximately the same size and mass as our Milky Way, but is estimated to have 2 1/2 to 10 times more stars, which would make it a much more densely packed galaxy. Andromeda was thought to be a nebula for centuries (millennia?) until 1755 when German philosopher Immanuel Kant hypothesized that it could be a galaxy similar to our own. In 1920, Heber Curtis spotted what we now call a supernova in Andromeda, and also supported the idea of “island universes”, thinking that spiral nebula were actually galaxies. Edwin Hubble finally demonstrated conclusively in 1925 that a very particular type of star, Cepheid Variables, were contained within “the Andromeda Nebula”, measured their distance, and determined that Andromeda had to be a completely separate galaxy from our own. So it has only been in the last 100 years that we have known about the existence of galaxies containing billions of stars.
M33 The Triangulum Galaxy, a Spiral Galaxy