M31 · Andromeda
The nearest major galaxy to the Milky Way, around 2.5 million light-years away.
Astronomy Lab · Deep-sky observing
Charles Messier and the Catalogue of Cosmic “False Alarms”
Charles Messier wanted to discover comets. Instead, he created one of astronomy's most famous catalogues — a collection of galaxies, nebulae and star clusters that observers still explore more than two centuries later.
Why make the catalogue?
Through an eighteenth-century telescope, a faint galaxy, nebula or
cluster could resemble a comet. Messier recorded these stationary
objects so that he — and other comet hunters — would not be fooled
by them again.
Charles Messier (1730–1817), comet hunter and creator of the catalogue
that bears his name.
From nuisance to treasure
Messier was trying not to observe these objects
In 1758 Messier encountered a faint, cloudy object in Taurus while following a comet. Unlike a comet, it did not move against the stars. That object became M1 — the Crab Nebula — and helped inspire a list of other stationary comet-like objects.
1758
M1 enters the story
The Crab Nebula becomes the first entry in what would develop into Messier's catalogue.
103
Messier-era objects
By the end of Messier's life, the published and compiled catalogue associated with his work contained 103 entries.
110
Modern catalogue
Later historical work expanded the accepted Messier list to the 110 objects recognised today.
What is in the catalogue?
These “fuzzy objects” are not all the same thing
Messier could catalogue how an object looked and where it appeared, but eighteenth-century astronomy could not yet reveal the true nature of most of them. Today we know that the catalogue mixes several very different classes of object.
Galaxies
Vast systems containing stars, gas, dust and dark matter. M31 and M51 are famous examples.
Open clusters
Relatively young, loosely bound groups of stars such as the Pleiades, M45.
Globular clusters
Dense, approximately spherical collections of old stars. M13 is one of the best-known examples.
Nebulae
Clouds of gas and dust with many different origins: stellar nurseries, planetary nebulae and supernova remnants all appear in the Messier catalogue.
Interactive explorer
Meet some of the most famous Messier objects
Choose a category and then select an object. These examples alone show how extraordinarily varied Messier's collection turned out to be.
M31 · Andromeda Galaxy
Explore the catalogue
Three very different worlds
Galaxy, cluster and planetary nebula
M13 · Hercules Cluster
A dense globular cluster containing an enormous population of old stars bound together by gravity.
M57 · Ring Nebula
A planetary nebula: glowing material expelled during the late evolution of a Sun-like star.
A spectacular example
M31: light from another galaxy
The Andromeda Galaxy is approximately 2.5 million light-years away. That means the light reaching your eyes tonight began its journey roughly 2.5 million years ago.
Although M31 appears as a faint patch to the unaided eye under a dark sky, photographs reveal a huge spiral galaxy. Its apparent extent on the sky is several times the diameter of the full Moon, although its faint outer regions are difficult to see visually.
The Messier Marathon
Can you observe all 110 objects in one night?
Around March, the geometry of the night sky makes it possible from favourable northern latitudes to attempt one of amateur astronomy's classic challenges: observing as many Messier objects as possible between dusk and dawn.
A complete Messier Marathon aims for all 110 objects. Success requires dark skies, careful planning, a favourable Moon phase, rapid navigation and — usually — quite a lot of coffee.
Start observing
You do not need a giant telescope
Start with bright objects
M31, M42 and M45 are excellent introductory Messier targets.
Use binoculars
Several large and bright Messier objects are excellent binocular
targets under sufficiently dark skies.
Know your field of view
Different targets vary enormously in apparent size. Use our
telescope field-of-view calculator to plan your observation.
Let your eyes adapt
Faint galaxies and nebulae become easier to detect after spending
time away from bright lights.
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