The Whirlpool galaxy also goes by the name M51, M51a, and NGC 5194. It has the distinguishing note of being the first galaxy to ever get an official label designation for its well-known spiral shape.

The galaxy is familiar to many and the Whirlpool is thought to be a classic design for the description of a spiral galaxy.

Research of the Whirlpool galaxy has been ongoing as astronomers have used it to study and learn about the interaction that it has with a dwarf galaxy that is close to it known as M51b.

The Whirlpool galaxy is part of the “Hunting Dogs” constellation known as Canes Venatici, and is one of the galaxies in the sky that is so bright that it can be viewed with low tech binoculars and telescopes, and even the naked eye.

When astronomers do use more sophisticated telescopes they can see the side of the Whirlpool spiral as it faces our Earth.

When astronomers choose to display images of a galaxy they often select the Whirlpool galaxy alongside of the Milky Way. It has winding arms that span out in graceful displays, almost looking like it is dancing through the universe.

Whilrpool Galaxy

The “arms” are gas, stars, and dust in long delicate tendrils. These are important because they are the nurseries for stars, compressing the materials that are required for the clusters of newly born stars in its galaxy.

Scientists theorize that the Whirlpool galaxy had an interaction with the small, yellow-colored NGC 5195 galaxy that exists in one of the tips of the outermost arms, and the interaction has made the arms of M51 prominent.

The idea is based on the appearance of M51, which almost seems like the smaller galaxy is pulling on the arm, triggering the new formation of stars with the tidal forces involved in the encounter.

The Hubble Space Telescope has taken images that display NGC 5195 crossing the path of the Whirlpool galaxy, something that has been happening for hundreds of millions of years.

Whirlpool Statistics:

Galaxy Type: Spiral
Designation: M51a or NGC 5194
Diameter: 60,000 light-years
Mass: 160 billion M☉
Constellation: Canes Venatici
Distance to Galactic Center: 23 million light-years


The Whirlpool galaxy is another galaxy that has been easily viewed from Earth for millennia. It has a magnitude of 8.4 which makes it bright enough to be seen from all over the globe.

However, in the past, many astronomers thought that the Milky Way galaxy was the limit of the universe and anything seen in the celestial skies was embedded in the Milky Way.

As time passed, astronomers believed that the other images that they saw in the night sky were “nebulae”. Charles Messier is credited for locating M51 in 1773, plotting it at 31 million light-years from our Earth in the Canes Venatici constellation.

Although the discovery of the Whirlpool galaxy was in 1773, it took until 1845 for the galaxy to receive an official designation and be acknowledged as a spiral galaxy.

The 3rd Earl of Rosse, William Parsons, was incredibly wealthy and purchased the biggest optical telescope in the world at that time. Using the telescope, he viewed the Whirlpool galaxy to define the spiral shape.

The Whirpool galaxy remains as one of the most popular among scientists and astronomers and holds the credit for being the first spiral galaxy to be officially identified as such.

Those that study the Whirlpool galaxy are particularly fascinated with its interactions with the dwarf galaxy neighbor, M51b.


Scientists have had a long-held debate over the distance of the Whirlpool galaxy from the Earth. Most astronomers agree that it is around 23 million light-years away, however, others had said that it could be in a range from 15-35 million light-years away.

Those that settled on the 23 million light-year number did so from the calculations based on data that was collected from an exploding supernovae in the Whirlpool galaxy.

Sketch of M51 by Lord Rosse in 1845

The event created small fluctuations in the instruments that are scientifically designed to detect cosmic objects, allowing sophisticated techniques of measurement.

Astrophysicists are particularly fascinated with the large percentage of supernova star explosions that occur in the Whirlpool galaxy.

The Hubble Space Telescope has taken images of M51 showing the infrared light red tones and the abundance of hydrogen in the regions that have a high percentage of star formations.

The telescope has also captured pictures of the blue color of hot, young stars as well as the older stars that appear in a yellow color. They also continue to focus on the interactivity between the Whirlpool galaxy and M51b, the dwarf neighbor galaxy.

The fact that the Whirlpool galaxy is so close has offered scientists an incredible opportunity to watch its structure as it creates new stars.

Astronomers have observed that, over time, the largest stars have an effect on the surrounding gas that causes it to radiate away.

This leaves the clusters of blue stars so that they remain within the arms of the Whirlpool galaxy, letting scientists accomplish long-term study.

Interesting Information:

The Whirlpool galaxy and its smaller neighbor, the dwarf galaxy of M51b have been merging for millions of years and the situation has caused the spiral arms of the Whirlpool galaxy to become misshapen.

Astronomers don’t know what the original shape of the dwarf galaxy was.

The dwarf galaxy of M51b is giving the Whirlpool galaxy an incredible amount of raw material that has created a lot of production of new stars in the galaxy’s center.

Similar to the Milky Way galaxy, the Whirlpool galaxy has a supermassive black hole in its center. The black hole is surrounded by dust rings that are in a constant state of new star creation.

The image of the Whirlpool Galaxy in visual light (left) and infrared light (right).

The activity is at such a high degree that it increases the brightness so that scientists have classified the Whirlpool galaxy as a “Seyfert galaxy.”

The companion dwarf galaxy M51b is eventually expected to become fully absorbed by the Whirlpool galaxy.  The two are currently connected with a bridge of gas and dust.

The effect of the dwarf galaxy M51b on the Whirlpool galaxy has been noted by scientists. As M51b passes by the Whirlpool galaxy the gravitational pull of M51b generates waves within the pancake-shaped disk of the Whirlpool galaxy.

These waves can be compared to those that happen when you throw a rock into a pond and it causes ripples.

The waves pass through the gas clouds that are orbiting the disk and squeeze the gas to the inner edge of each of the Whirlpool galaxy’s arms.

As all of this occurs the dusty dark material appears like an Earth storm, with the eventual collapse of the dense clouds that herald the beginning of a star being born. This interaction has been coined as a “close encounter.”

Exploration and Study:

In 1845, William Parsons used a 72-inch reflector telescope, he created a drawing of the Whirlpool galaxy that depicted his observations.

It is considered to be a mid-19th century astronomy classic work and was used as a baseline for future studies. Parsons continued his work on what he thought was a “spiral nebula,” in within 5 years had discovered 14 more of the same type of objects.

This was during the time when astronomers weren’t sure if the nebula were part of the Milky Way galaxy or objects that were completely independent.

In the 1920’s, Edwin Hubble charted the M31 cosmic distance using the Cepheid variable stars. It was during that time that scientists began to acknowledge that there were distance galaxies apart from the Milky Way.

Important Events:

In 1994, 2005, and 2011, the Whirlpool galaxy has had a huge number of supernovas. The organization Skywatchers has been recording the events.

Scientists are unsure exactly why there has been such an increase in supernova activity. The 2011 supernova was examined after its brightest moment to see if they could figure out the source of the explosive behavior.

Using the Hubble Space Telescope, astronomers searched a supergiant yellow star that was present prior to the supernova explosion and then gone afterwards.

This was uncommon behavior as most supergiant stars don’t go nova when their lifecycle is done, however, the astronomer team indicated that there is a distinct possibility that this was a binary star.

In the case of a binary condition, the companion star would have been hot enough to pull some of the mass away from the supergiant.

Over time, this would cause a destabilization of the star which could result in an explosion.

The Hubble Space Telescope doesn’t view the stars in ultraviolet light, which was the range required to see the blue companion star.

This situation, combined with the other supernova explosions has prompted scientists to recognize the requirement for additional study of the evolution of binary star explosions.

The Chanra X-Ray Observatory took an image in 2015 of the Whirlpool galaxy that involved over 250 hours of observation time.

The space telescope used five times the number of sources that had been used in prior studies which totaled to 500 X-ray sources. Astronomers believe that a minimum of ten of the sources were derived from black holes.

Facts about Whirlpool Galaxy for Kids:

  • It’s estimated that the Whirlpool galaxy has over 100 billion stars.
  • Charles Messier was looking for comets in the celestial sky and, as he was trying to continue his charting process he discovered the Whirlpool galaxy in 1773.
  • William Parsons was incredibly wealthy and in 1845 he purchased one of the biggest and best telescopes in the world. He set up the telescope at Birr Castle, Ireland and observed the Whirlpool galaxy and its dwarf companion galaxy, identifying the spiral structure.
  • Scientists think than the companion dwarf galaxy, M51b and the Whirlpool galaxy have already passed each other and possibly passed through each other at least one time. There has been major disruption in the structure of M51b due to the cosmic dance that the two are having. The arms of the Whirlpool galaxy have also been distorted.
  • Astronomers believe that the collision with the dwarf companion galaxy of M51b is causing an explosion in the birth of new stars in the Whirlpool galaxy.
  • The Whirlpool galaxy has a mass that is huge. Its total mass is around 160 billion times that of our sun.
  • The mass of the Whirlpool galaxy might be huge, but the galaxy’s size is only about 35% of the Milky Way galaxy.
  • If you wanted to find the Whirlpool galaxy you would need to make sure that you go out on a dark night with very little light interference from towns or cities. Look towards the southeast of the Big Dipper to find the Canes Venatici constellation.
  • Astronomers know that the core of the Whirlpool galaxy is incredibly active. They believe that this may be the reason that it is so bright and demonstrates strong infrared spectrum emissions.

Pop Culture:

The Whirlpool galaxy, also known as M51, is one of the most visually appealing galaxies that we have discovered. It’s long been used in books, movies, television, and games as a source and backdrop for many science fiction stories.

The Homeworld series of games uses the Whirlpool galaxy as a basis, with the first game taking players on a trip through the galaxy to the core and outer rim.

The video game Ōkami has an appearance by the Whirlpool galaxy when the main character summons the galaxy by creating an oceanic whirlpool for travel.

The television series Roswell has three alien teenage protagonists that are supposed to originate from the Whirlwind Galaxy’s Five Worlds.

Donald Moffitt’s novels The Genesis Quest and Second Genesis features humans from the future that all of the knowledge of humanity to the Virgo supercluster to aliens in the M51 galaxy.

The Mighty Morphin’ Power Ranges feature Master Vile, who is supposed to be the ruler of the Whirlpool galaxy.