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Monday, September 9, 2019

Amazing photo from NASA

Spitzer Snaps Beautiful Image of Messier 81

This infrared image taken by NASA’s Spitzer Space Telescope shows a spiral galaxy called Messier 81. Image credit: NASA / JPL-Caltech.
This infrared image taken by NASA’s Spitzer Space Telescope shows a spiral galaxy called Messier 81. Image credit: NASA / JPL-Caltech.
This infrared image taken by NASA’s Spitzer Space Telescope shows a spiral galaxy called Messier 81. Image credit: NASA / JPL-Caltech.

Messier 81 was discovered on December 31, 1774 by the German astronomer Johann Elert Bode.
Also known as M81, LEDA 28630 or NGC 3031, this galaxy is located 11.6 million light-years from Earth and has an apparent magnitude of 6.9.

Messier 81 has a diameter of 90,000 light-years, about half the size of our own Milky Way Galaxy.
It is the largest galaxy in the M81 Group, a gathering of 34 galaxies located in the northern constellation of Ursa Major.


The galaxy’s spiral arms, which wind all the way down into its 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 galaxy’s central bulge contains much older, redder stars. It is significantly larger than the Milky Way’s bulge.

A supermassive black hole of 70 million solar masses resides at the center of Messier 81 and is about 15 times the mass of the Milky Way’s central black hole.

“The Spitzer infrared image of Messier 81 is a composite mosaic combining data from the Infrared Array Camera at wavelengths of 3.6/4.5 microns (blue/cyan) and 8 microns (green) with data from the Multiband Imaging Photometer at 24 microns (red),” NASA astronomers said.

“The 3.6-micron near-infrared data (blue) traces the distribution of stars, although the 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 Messier 81.”
“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, carbonaceous grains and polycyclic aromatic hydrocarbons and trace the gas distribution in Messier 81.”

“The well-mixed gas and dust provide a reservoir of raw materials for future star formation.”