M 101
Pinwheel Galaxy
Pinwheel Galaxy, also known as Messier 101 (M101) or NGC 5457, is a “grand design” spiral galaxy located approximately 21 to 25 million light-years from Earth in the constellation Ursa Major. It is one of the most prominent face-on spiral galaxies visible from the Northern Hemisphere.
Key Characteristics
Size and Structure:
M101 is an enormous galaxy with a diameter of roughly 170,000 light-years, making it nearly twice the size of our Milky Way. It is estimated to contain at least one trillion stars.
Discovery:
It was discovered by Pierre Méchain in 1781 and subsequently included in Charles Messier’s famous Messier Catalogue.
Asymmetry:
The galaxy is notably asymmetrical, with its core displaced from the center of its disk. This is likely caused by tidal forces from gravitational interactions with its six companion galaxies.
Star Formation:
Its spiral arms are densely packed with bright blue clusters of newborn stars and pinkish H II regions (intense star-forming nebulae).
Recent Events:
Supernova SN 2023ixf: In May 2023, a Type II supernova was discovered in one of M101’s spiral arms by amateur astronomer Koichi Itagaki. It became the closest supernova to Earth in several years and was a popular target for backyard astrophotography throughout 2023 and 2024.