Pinwheel Galaxy Facts

If you know how to find the Big Dipper in the night sky, you can find where the Pinwheel Galaxy is located.

It is in the constellation of Ursa Major, also known as the Great Bear or the Big Dipper.

We estimate that the Pinwheel Galaxy is around 21 million light-years from Earth and that’s considered to be one of the closest galaxies to us.
The Milky Way Galaxy is half of the size of the Pinwheel Galaxy. It is thought to contain over a trillion stars.

Pinwheel Galaxy Profile

Constellation:Ursa Major
Also known as:Messier 101, M101 or NGC 5457
Type:Spiral Galaxy
Diameter:170,000 light years
Distance:21 Million light years
Mass:1,000 billion M☉
Number of Stars:1 trillion

Who discovered the Pinwheel Galaxy

Named after its shape, it is one of the spiral galaxies just like the Milky Way Galaxy. The Pinwheel Galaxy was discovered by Pierre Méchain in 1781.

Although Pierre was an astronomer, he was also interested in hunting comets and was given credit for discovering a lot of other celestial bodies including eight comets and many globular bodies.

The scientific name for the Pinwheel Galaxy is M101, Messier 101, or NGC 5457.


Spiral galaxies are known to produce a lot of stars and the Pinwheel Galaxy has over 3,000 locations in its “arms” where there are star nurseries.

These areas are called Hll regions and are named because they have a lot of hydrogen content. Stars are made up of mostly helium and hydrogen.

The middle section of the Pinwheel Galaxy is called the “central bulge,” and it has a mass that is equal to almost 3 billion suns.

The central bulge doesn’t produce very many stars. When a star dies, it does so with a huge, bright explosion called a supernova.


They can be so bright that they block out the ability to see other galaxies. Most of the heavy metal elements in the universe are due to supernovas.

The scientific community has recorded at least four of these supernovas in the Pinwheel Galaxy.

In 2015, a Romanian astronomer reported a red nova in the Pinwheel Galaxy. These happen when two stars collide and then create a new star.

Center of the Galaxy

One of the unique features of the Pinwheel Galaxy is that no one has been able to detect a black hole at the center of the galaxy. Instead of a black hole, the Pinwheel Galaxy seems to have x-ray sources that are called stellar-mass black holes.

When stars die, all of their material and elements fall into the stellar-mass black holes and heats up, throwing off x-rays. The unusual shape of the Pinwheel Galaxy was created by light and gas clouds that are between two big orbiting stars that are close together.


The ESA (European Space Agency) and NASA released a photo in 2006 of the Pinwheel Galaxy that was the largest to date, and had the most details ever seen.

The Hubble Space Telescope took the image and NASA indicated that the photo included several layers.

They said it was like looking at the galaxy when you were wearing night-vision goggles, x-ray vision, an ultra-violet camera, and a regular camera at the same time.

Facts about the Pinwheel Galaxy

  • The Pinwheel Galaxy is also called the Face-On Spiral Galaxy.
  • With a diameter of nearing 170,000 light-years across, the Pinwheel Galaxy is considered to be massive.
  • The mass of the Pinwheel Galaxy is equal to 100 billion solar masses or 100 billion suns.
  • When you look at the Pinwheel Galaxy through your telescope, you are seeing light that traveled to the Earth 21 million years ago.
  • Because the Pinwheel Galaxy does have a kind of bar at the center, scientists call it a weekly-barred spiral galaxy.
  • The central bulge of the Pinwheel Galaxy is small when compared to the rest of its size.
  • It’s thought that the Pinwheel Galaxy may have had some kind of interaction with another galaxy in the past due to one side being asymmetrical.

Instructions on how to see the Pinwheel Galaxy:

  • First – find the Big Dipper in the night sky.
  • Locate the tail or handle and find the last two stars.
  • Draw an imaginary point at the center of those two stars.
  • Using that point, draw another imaginary line straight up until the point where the top point of the line creates an equilateral triangle with the two stars.
  • You have now found where the Pinwheel Galaxy sits.


  • What kind of galaxy have scientists designated the Pinwheel Galaxy?
    weekly-barred spiral galaxy
  • Where are the stars born in the Pinwheel Galaxy?
    in its arms
  • How many supernovas have been discovered (so far) to have occurred in the Pinwheel Galaxy?
  • How far away is the Pinwheel Galaxy from Earth?
    21 million light-years
  • Where would you start to look in the night sky to find the Pinwheel Galaxy?
    the Big Dipper, also known as the Great Bear
  • The Milky Way Galaxy is how big compared to the Pinwheel Galaxy?
    half its size