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. It was created using 51 different space photos, along with some extra pictures taken from Earth. The Pinwheel Galaxy is a great example of how scientists study galaxies to learn more about the universe.

Discovery

Pierre Méchain discovered the Pinwheel Galaxy in 1781 and told Charles Messier about it. Messier then added it to his famous list of objects. Later, an astronomer named William Herschel looked at the galaxy with his telescopes and noticed something special about its appearance. In the 1800s, another astronomer named Lord Rosse used an even bigger telescope and was the first to draw the galaxy's spiral shape. Today, you can sometimes see the Pinwheel Galaxy with just binoculars or a small telescope, but you need a really good telescope to see its beautiful spiral arms clearly.

William Herschel Lord Rosse Newtonian reflector binoculars

Structure and composition

The Pinwheel Galaxy, also known as M101, is a huge galaxy about 252,000 light-years wide, much bigger than our Milky Way. It contains roughly a trillion stars and has a disk with a mass of about 100 billion times that of our Sun. Like the Andromeda Galaxy, it has lots of areas where new stars are born, called H II regions, which glow brightly because of very hot young stars.

M101 looks a bit lopsided because of gravity pulling from nearby galaxies. This pulling makes more stars form in its spiral arms. Scientists have found about 150 dense groups of old stars, called globular clusters, orbiting the galaxy.

Companion galaxies

The Pinwheel Galaxy, also known as 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 and their gravity may have helped create the beautiful 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 and was one of the brightest supernovae seen that year. 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 how stars live and die.