An Infrared View of the M81 Galaxy

Full Infrared View of the M81 Galaxy

Located in the northern constellation of Ursa Major, which also includes the Big Dipper, nearby galaxy Messier 81 is easily visible through binoculars or a small telescope. M81 is located at a distance of 12 million light-years.

M81 was one of the first publicly released datasets soon after the launch of the Spitzer Space Telescope in August 2003. On the occasion of Spitzer’s 16th anniversary this new image revisits this iconic object with extended observations and improved processing.

This Spitzer infrared image is a composite mosaic combining data from the Infrared Array Camera (IRAC) at wavelengths of 3.6/4.5 microns (blue/cyan) and 8 microns (green) with data from the Multiband Imaging Photometer (MIPS) at 24 microns (red).

The 3.6-micron near-infrared data (blue) traces the distribution of stars, although the Spitzer image is virtually unaffected by obscuring dust and reveals a very smooth stellar mass distribution, with the spiral arms relatively subdued.

As one moves to longer wavelengths, the spiral arms become the dominant feature of the galaxy. The 8-micron emission (green) is dominated by infrared light radiated by hot dust that has been heated by nearby luminous stars. Dust in the galaxy is bathed by ultraviolet and visible light from nearby stars. Upon absorbing an ultraviolet or visible-light photon, a dust grain is heated and re-emits the energy at longer infrared wavelengths. The dust particles are composed of silicates (chemically similar to beach sand), carbonaceous grains and polycyclic aromatic hydrocarbons and trace the gas distribution in the galaxy. The well-mixed gas (which is best detected at radio wavelengths) and dust provide a reservoir of raw materials for future star formation.

Image Credit: NASA/JPL-Caltech

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18 thoughts on “An Infrared View of the M81 Galaxy

  1. “Supermassive black hole feedback is thought to be responsible for the lack of star formation, or quiescence, in a significant fraction of galaxies. ”
    https://arxiv.org/abs/1906.02747

    Here a galactic scale feedback mechanism is invoked.
    Our galaxy has a 4 million solar-mass object, this M81 with 9 million, M87 with 6 a billion solar-mass object (the famous EHT image).

    Now where have I heard of feedback before? It seems to crop up everywhere.

  2. What a beauty.

    “The 3.6-micron near-infrared data (blue) traces the distribution of stars, although the Spitzer image is virtually unaffected by obscuring dust and reveals a very smooth stellar mass distribution, with

    the spiral arms relatively subdued.

    As one moves to longer wavelengths, the spiral arms become the dominant feature of the galaxy.”

    A goose and her goslings: https://www.google.com/search?client=ms-android-huawei&sxsrf=ACYBGNTKnu3XUX70Lt-0ORBV_3fes-dJUQ%3A1567773219468&ei=I1JyXZCXHK6MrwSGn7e4Bw&q=goose+and+her+goslings+videos&oq=goose+and+her+goslings+videos&gs_l=mobile-gws-wiz-serp.

  3. M81 –one of my favorites as it can be seen reasonably well even in a small telescope. Similar in size to the Milky Way, but a bit more “mature” w/most of the new star formation limited to well outside the central bulge.

  4. Whenever I used to watch a satellite picture of a hurricane, I would imagine I was watching how a galaxy would behave in space, but I guess since galaxies are supposed to rotate as a single body due to all that dark matter, I can’t really apply that comparison, can I.

    • Galaxies spin faster in the center, slower at the edges, so for 50 years or so, no one could explain why the spiral arms don’t just wind themselves tightly in the inner regions. Finally a fluid mechanics guy (C.C. Lin of MIT) approached it as a fluid instead of a bunch of particles (stars) and came up with the accepted explanation–the spiral arms we see are a pattern of density waves, not a physical rotating bunch of stars, and the PATTERN rotates more or less as a solid plate. As the density wave hits a spot with enough dust and gas to form stars, they form and thus light up the density wave. I was a third-generation astrophysicist, as CC LIn taught Frank Shu, who taught Chi Yuan, who taught me.

      • ” I was a third-generation astrophysicist, as CC LIn taught Frank Shu, who taught Chi Yuan, who taught me.”

        And thanks for teaching me. 🙂

      • The density waves are working in what fluid, exactly? So we should be looking a little harder at proposal made more than 100 years ago that there is, around each visible object, a large sphere of a different sort of material whose existence can be inferred, not observed, and around that, a sphere of a third form of matter that “very much larger”.

        The black hole or neutron star in the center of a galaxy will have these features too, and it is possible that the radial limit of a dense form of the material in the second sphere is at the tips of the bar in a barred spiral galaxy. The “density” (which might have different states, like H2O) of that second material may impart the spin of the bar so that it doesn’t spiral like the region outside. The third type of material (which I call Darker Matter) provides the “fluid” which can vibrate and oscillate and produce the patterns you mention. It may extend far beyond the visible radius.

        As many investigators have already noticed, Dark Matter is inadequate to explain the appearance and movements within galaxies. With three types of matter, the third being a superfluid, additional explanations may be considered.

        The related question is whether or not an absolute vacuum within a physical space can exist. There is a lot left to think about.

  5. “Upon absorbing an ultraviolet or visible-light photon…is heated and re-emits the energy at longer infrared wavelengths. “

    Hey, just like the carbon in our atmosphere!

    @Griff, do I need the /sarc tag?

  6. Interesting that just where the supermassive black hole should be located at the center of the hub it is bright white with pinkish hue.

    • That’s because the CO2 in the black hole has caused it be a superheated black hole. That’s what happens when you use fossil fuels.

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