Astronomy Charles_Messier

Published on September 6th, 2011 | by Carl Mundy


Charles Messier’s famous list of 110 astronomical objects to ignore and why he was wrong

Today we look at just a few of the breathtaking 110 astronomical objects that Charles Messier catalogued so that he could ignore them in his search for comets…

An eighteenth century French astronomer by the name of Charles Messier produced a catalogue of objects in the night sky that he just wasn’t interested in. He was a comet hunter. Searching for the balls of rock and ice that orbit the Sun over tens, hundreds and even hundreds of thousands of years, Messier wanted to easily distinguish the frustratingly comet-like objects that appeared static in the night sky from actual comets that danced across the sky and that were so sought after. Messier himself compiled a list of 102 objects that was later added to using Messier’s own notes.

These objects were mostly star clusters, galaxies, nebulae and supernova remnants and while it was created so that other comet hunters like himself could ignore them, astronomers today regularly train their telescopes on these objects and in doing so set eyes on some of the most breathtaking sights in the observable universe. Here we look at some of the most interesting of the 110 objects that Messier wanted us to ignore, and explain the origins behind their formation and creation.

#1 The Crab Nebula

In the 11th century, Arab and Chinese astronomers recorded a bright light in the sky which we now know was a supernova that gave birth to what we now call the Crab Nebula, or M1 if we are referring to Messier’s catalogue. A star at the center of the nebula collapsed and expelled its material at up to ~10% the speed of light into the space around it. This creates shock waves which sweep up the material from the star and the space it travels through which produces the supernova remnant that we observe today.

At the center of the nebula is a spinning neutron star, called the Crab Pulsar, which rotates around 30 times a second, emitting pulses of radiation with every turn which we can detect here on Earth. These pulses of radiation have been used to probe the Sun’s corona as well as the atmosphere of Saturn’s moon Titan.

#16 The Eagle Nebula

Named after its apparent eagle-shape, this cluster of young stars, gas and dust is famous because of an image taken by Hubble in 1995. This image, dubbed the ‘Pillars of Creation’, showed a particular part of the Eagle Nebula, or M16, in which light-years long pillars of gas and dust were known to be giving birth to stars. This star-forming region is around 6,500 light-years away and some of the stars in the region can be seen easily with good binoculars.

Within the Eagle Nebula, the gas and dust collapse into dense regions called globules, or molecular clouds, which appear like cocoons within which stars are believed to begin forming. These can easily be seen in the ‘Pillars of Creation’ image and in a few other images taken by Hubble.

#22 Sagittarius Cluster

From the Latin for ‘small sphere’, globular clusters are spherical collections of stars that orbit the center of galaxies, much like a galactic satellite, unlike open clusters which orbit within the disk of the galaxy. At around 11,000 light-years away the Sagittarius Cluster is the brightest globular cluster visible from mid-northern latitudes, and one of the brightest in the entire night sky.

Star clusters such as these appear as a faint blurry glow in the night sky to the naked eye, and even with some binoculars. Through a telescope these fields of stars glimmer like a scattering of precious jewels under light.

#31 Andromeda Galaxy

Approximately 2.5 million light-years from Earth, the Andromeda galaxy (M31) is the nearest spiral galaxy to our own Milky Way. While it can appear up to six times as wide as a full moon in the night sky through a telescope, only the bright central region is visible to the naked eye on a clear night.

The Andromeda galaxy is one of only a few galaxies that are moving towards our own. Because of this, our own galaxy will collide with Andromeda in around four and a half billion years but what will happen during the collision is currently unknown. Until that time comes we can keep worrying about the weather at the weekend.

#57 The Ring Nebula

Near the end of a star’s lifetime it swells to hundreds of times the radius of our own Sun as it exhausts the supply of hydrogen in the core. When this occurs, it moves to fusing hydrogen in a shell further from the core and ‘puffs’ up in doing so. Eventually, this red giant can expel its material into the interstellar space around it creating planetary nebulae; the gaseous remains of the red giant star. One such example of this is the Ring Nebula.

One of the most visually stunning nebula you can observe, the blue-green inner  is caused by the ionisation (stripping of electrons) of oxygen whereas the outer red-orange shell is mainly produced from hydrogen emission and ionisation of nitrogen. The star that produced what we see today is on its way to becoming a white dwarf, composed mainly of carbon and oxygen and can be seen at the center of the nebula above.

#78 Messier 78

Although it may not be known by any particular name, this amazing sight can be found in one of the most recognisable parts of the night sky; the Orion constellation. This reflection nebula is formed by the large amount of gas and dust reflecting light from nearby stars.

There are two main stars within the nebula that are responsible for making it visible. Through a small telescope, the blue detail should be visible. M78 should not be confused with the equally beautiful sight that is the Orion Nebula (M42).

#101 The Pinwheel Galaxy

Like our own galaxy the Milky Way, M101 is a spiral galaxy positioned face on to us at a distance of about 20 million light-years away. It is thought that in the recent (in galactic terms) the Pinwheel galaxy had a near collision with another galaxy which caused the asymmetry seen in its spiral arms. This interaction is thought to have triggered a wave of star formation throughout the galaxy.

In August 2011, a type Ia supernova event was observed in the Pinwheel galaxy. This is when a white dwarf gains mass sending it over a limit called the Chandrasekhar limit which results in the white dwarf’s collapse and the bright explosion we observe in the night sky. At its absolute brightest this supernova will be as bright as 2.5 billion Suns, but still only visible through small telescopes here on Earth.

Further Your Knowledge

The Messier catalogue is still used to this day to refer to objects in the night sky, but it is not the only catalogue used by astronomers. The most widely used is the New General Catalogue, or NGC, which lists nearly 8,000 objects at time of writing.  Check out the following objects in the NGC!

  • What type of nebula is NGC40, the Bow-Tie Nebula?
  • How far in light-years is the spiral galaxy NGC88 from Earth?
  • What NGC number corresponds to the Crab Nebula?

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About the Author

Astronomy PhD student from the UK with a passion for astronomy and science outreach projects. Involved with weekly science-based radio programme The Science Show on University Radio Nottingham (URN).

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