Summer is a great time for pinwheels. Perhaps the most famous is the Pinwheel Galaxy, M101. The Pinwheel is a spiral galaxy like our own Milky Way, though nearly twice the size of the Milky Way. Galaxies like the Milky Way and Pinwheel are important because they provide an active environment for massive star formation, and their deep gravitational wells trap the enriched material produced by the explosive evolution of these stars, ultimately driving the chemical evolution of the cosmos. The galactic environment is complex and best studied by a multi-wavelength approach: hot solid dust grains glowing in the infrared, stars shining brightly in the optical, massive stars pumping out enormous amounts of high-energy ultraviolet light, and superhot gas produced by stellar supernovae, and the neutron star and black hole descendents of massive star evolution. The composite of M101 shown above shows four different, combined views of the galaxy obtained by four NASA space observatories, covering all these different phenomena: an infrared observation by the Spitzer Space Telescope (red), a sharp-eyed optical image by the Hubble Space Telescope, an ultraviolet image by GALEX, and a sharp X-ray image by the Chandra X-ray Observatory. A good way to celebrate the unofficial start of summer in the northern hemisphere.
CXC: M101: A Pinwheel in Many Colors
Spitzer: A Pinwheel Galaxy Rainbow (M101)
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