Traverse City Record-Eagle


M81 and M82

Ed HahnenbergM81, a spectacular spiral galaxy in the constellation Ursa Major, is about the apparent size of the full moon, which we are one day from … Sept. 30th. I imaged it with previous equipment, but not with the present scope and camera.

Two things were working against me. I had misplaced my 8 GB flash drive … perhaps it accidentally fell into the wastebasket at home. So, I had to save it to My Pictures on my computer. This actually turned out to be fortunate because I could see the thumbnail images after exposure. Meteors, airplanes, and satellites leave star trails in an image and when one combines a folder of 30 or so, one such image can spoil the final picture. If one such image is seen, it has to be deleted.

I would head for Radio Shack for a flash Saturday so I could process my M81 file.

The other problem was the location in the sky of M81. Since I have my study room north of the dome and the bottom opening bumps into it if I want to image northerly targets, I had to detach the folding opening to image my target. Not difficult, just annoying. The picture below shows the bottom opening dropped down in an image from 2008, the day the dome was added.

I had contacted Terry Platt, owner of the Starlight Xpress company in the UK which produced the one-shot color camera I use. I asked him if binning 2 X 2 was a good idea for color reproduction. He said color imaging in Maxim DL should be done in 1 X 1 mode. He said that I could get good black and white images, but not good color ones. With that cautionary advice, I decided to go ahead anyway with 30 exposures, each a minute in length, binned at 2 X 2, and process the batch in Photoshop, come what may. 2 X 2 binning cuts the exposure time in half as I pointed out in my previous post.

I processed the batch and hoped another galaxy, M82, would show up in the same image. It did. M82 is the prototype nearby starburst galaxy about 12 million light-years away. This galaxy is five times as bright as the whole Milky Way and one hundred times as bright as our galaxy’s center.

Below is my color image of both M81 and M82. Click on it for a LARGER view.

A bit more information about M 81 …

Due to its proximity to Earth, large size and active galactic nucleus, M 81 has been studied extensively. According to research gained from imaging M 81 with the Hubble telescope, the spiral arms, which wind all the way down into the nucleus, are made up of young, bluish, hot stars formed in the past few million years. They also host a population of stars formed in an episode of star formation that started about 600 million years ago. The greenish regions are dense areas of bright star formation. The ultraviolet light from hot young stars are fluorescing the surrounding clouds of hydrogen gas. A number of sinuous dust lanes also wind all the way into the nucleus of M81.

The galaxy’s central bulge contains much older, redder stars. It is significantly larger than the Milky Way’s bulge. A black hole of 70 million solar masses resides at the center of M81. The black hole is about 15 times the mass of the Milky Way’s black hole.

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