Celestial hemisphere:  Northern  ·  Constellation: Ursa Major (UMa)  ·  Contains:  M 101  ·  NGC 5457  ·  NGC 5461  ·  NGC 5471  ·  NGC 5477
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The Pinwheel Galaxy, Bret Waddington
The Pinwheel Galaxy
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The Pinwheel Galaxy

Getting plate-solving status, please wait...
The Pinwheel Galaxy, Bret Waddington
The Pinwheel Galaxy
Powered byPixInsight

The Pinwheel Galaxy

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Description

M101 is a large galaxy, with a diameter of 170,000 light-years. By comparison, the Milky Way has a diameter of 258,000 light years. It has around a trillion stars, twice the number in the Milky Way. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses.

M101 has a high population of H II regions, many of which are very large and bright. H II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force where stars form. H II regions are ionized by large numbers of extremely bright and hot young stars; those in M101 are capable of creating hot superbubbles. In a 1990 study, 1264 H II regions were cataloged in the galaxy. Three are prominent enough to receive New General Catalogue numbers - NGC 5461, NGC 5462, and NGC 5471.

M101 is asymmetrical due to the tidal forces from interactions with its companion galaxies. These gravitational interactions compress interstellar hydrogen gas, which then triggers strong star formation activity in M101's spiral arms that can be detected in ultraviolet images.

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The Pinwheel Galaxy, Bret Waddington

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