Pinwheel Galaxy

The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a beautiful spiral galaxy that looks like a pinwheel when seen from above. It is located 21 million light-years away from Earth in the constellation Ursa Major.

This galaxy was discovered by Pierre Méchain in 1781 and added to the Messier Catalogue by Charles Messier.

In 2006, NASA and the European Space Agency shared an amazing picture of the Pinwheel Galaxy taken by the Hubble Space Telescope. This picture was the largest and most detailed image of a galaxy ever taken by Hubble at that time. The Pinwheel Galaxy helps scientists learn more about the universe.

Discovery

Pierre Méchain found the Pinwheel Galaxy in 1781 and told Charles Messier. Messier added it to his list of objects. Later, William Herschel used his telescopes and saw something special about its looks. In the 1800s, Lord Rosse used a bigger telescope and was the first to draw the galaxy's spiral shape. Today, you can sometimes see the Pinwheel Galaxy with binoculars or a small telescope, but you need a good telescope to see its spiral arms clearly.

William Herschel Lord Rosse Newtonian reflector binoculars

Structure and composition

The Pinwheel Galaxy, also called M101, is a very big galaxy about 252,000 light-years wide. It is much bigger than our Milky Way. It has about a trillion stars. Its disk weighs about 100 billion times as much as our Sun. Like the Andromeda Galaxy, it has places where new stars are born. These areas, called H II regions, glow because of hot young stars.

M101 looks a little uneven because gravity from nearby galaxies pulls on it. This pulling helps make more stars in its spiral arms. Scientists have found about 150 dense groups of old stars, called globular clusters, moving around the galaxy.

Companion galaxies

The Pinwheel Galaxy, also called M101, has six companion galaxies nearby: NGC 5204, NGC 5474, NGC 5477, NGC 5585, UGC 8837, and UGC 9405. These galaxies are part of a group called the M101 Group. Their gravity may have helped shape the spiral arms of the Pinwheel Galaxy.

Supernovae and luminous red nova

Astronomers have found six bright explosions called supernovae in the Pinwheel Galaxy. These explosions happen when stars reach the end of their lives and burst brightly. Some of these supernovae include SN 1909A, found in 1909, and SN 1970G, found in 1970. More recently, SN 2011fe was discovered in 2011. Another explosion, called a luminous red nova and named M101 OT2015-1, was found in 2015. The latest, SN 2023ixf, was spotted in May 2023. These events help scientists learn more about stars.