The Messier Catalog

The complete table

All 110 objects, sortable by any column. The distance column gives the accepted distance in light-years; where the literature spans a range, the guide sections below quote it honestly. "Best month" is when the object crosses the evening sky's meridian at about 9 pm, the most comfortable time to observe it. The gear column is the minimum that shows the object at all, not what does it justice.

Messier the comet hunter

Charles Messier hunted comets from a tower of the Hotel de Cluny in central Paris, and by the standards of his century he was superb at it: he discovered 13 outright and shared credit for several more. Comets in a small 18th-century refractor look like dim, fuzzy patches, and the sky is scattered with dim, fuzzy patches that never move. After wasting nights on the Crab Nebula in 1758 while chasing the predicted return of Halley's comet, Messier began writing down the impostors so he could ignore them. That working list grew into the catalog: 45 objects in the 1774 first edition, 68 by 1780, and 103 in the final 1781 publication, with colleagues, above all Pierre Mechain, contributing many of the later finds.

The 20th century finished the job. Historians restored seven objects Messier and Mechain had observed but never formally numbered: M104 (added in 1921), M105 through M107 (1947), M108 and M109 (1953), and finally M110 in 1966. That is how a comet hunter's list of things to avoid ended at 110 entries, and why the numbering wanders across the sky in no particular order: it follows the sequence of discovery, not geography.

The catalog's lasting value comes from its limitations. Messier worked with telescopes no more capable than a modern beginner's instrument, under Paris skies, from latitude 49 degrees north. Whatever he could see, you can see. That is why the Messier catalog, and not some deeper professional list, remains the standard first tour of the deep sky: it is a complete inventory of the northern sky's showpieces, pre-filtered by a small telescope. The same geography explains what is missing: nothing in the catalog sits south of about declination -35, so southern wonders like Omega Centauri and the Carina Nebula are absent. They live in later lists, chiefly the Caldwell catalog, which this site's Sky Map also plots.

What the 110 objects actually are

Messier had no idea what most of his objects were; nobody did until the 20th century. The list turns out to sample almost everything the deep sky contains:

• Open clusters (26). Young families of stars, from a few dozen to a few thousand, still traveling together in the galaxy's disk after being born from one cloud. Most will drift apart within a few hundred million years. They range from naked-eye spectacles like the Pleiades to rich telescopic fields like M37.
• Globular clusters (29). Ancient spherical swarms of hundreds of thousands of stars orbiting the Milky Way's halo, most of them 11 to 13 billion years old, older than the galaxy's disk itself. In the eyepiece they grow from a fuzzy ball to a sugar-spill of resolved stars as aperture increases.
• Bright nebulae (8). Clouds of gas and dust: some glowing with their own light where new stars ionize them (Orion, the Lagoon), one shining only by reflected starlight (M78), and one, the Crab, the debris of an exploded star. The catalog's single supernova remnant is also its first entry.
• Planetary nebulae (4). The cast-off outer layers of dying Sun-like stars, glowing for a few tens of thousands of years while the exposed core fades to a white dwarf. The name is an 18th-century accident: in early telescopes their small disks resembled planets. They have nothing to do with planets.
• Galaxies (40). Entire star systems far beyond the Milky Way, from our neighbor Andromeda at 2.5 million light-years to M109 at roughly 84 million. The catalog's galaxies crowd the spring sky, where the Virgo Cluster pours across the border into Coma Berenices.
• The curiosities (3). One naked-eye window through the Milky Way's dust (the M24 star cloud), one double star cataloged by mistake (M40), and one four-star asterism (M73). The debated entry M102 is counted with the galaxies and discussed below.

The catalog also has a geography. Globular clusters swarm the summer sky toward Sagittarius, Scorpius and Ophiuchus, because that is the direction of the galactic center they orbit. Open clusters and nebulae ride the winter and summer Milky Way, because they live in the galaxy's star-forming disk. And the galaxies fill the spring sky, where we look up and out of our own galaxy's dusty plane into clear intergalactic space. Learn that pattern and the catalog stops being a list and becomes a map of how the galaxy is put together.

The Messier marathon

Around the March new moon, and only then, the geometry of the sky allows a determined observer at the right latitude to see every Messier object in a single night. The Sun sits in Pisces and Aquarius, the one stretch of sky nearly empty of Messier objects, so everything else parades through the darkness between dusk and dawn. That all-night pursuit is the Messier marathon.

The race has a brutal start and finish. At dusk you have minutes to catch M74 and M77, low in the west in fading twilight, two of the hardest objects in the catalog at the worst possible moment. The night then unrolls eastward: the autumn objects, the winter showpieces, the spring galaxies (most marathoners hit the Virgo Cluster after midnight), the summer globulars in the small hours, and finally a dawn scramble for M30, rising just ahead of the Sun. Miss the window at either end and a perfect score is gone.

Honesty about the conditions: a full 110-object marathon is realistic only between about latitude 20 and 40 degrees north; farther north, the southernmost objects barely rise, and farther south, the dusk and dawn brackets fail. It also demands a dark site with clean horizons, and it is a sport, not an observing program. Nobody appreciates the Ring Nebula in the 40 seconds a marathon schedule allows. Most observers get more from a half marathon, or from taking a season's objects at a comfortable pace with the month column in the table above.

Mistakes, gaps and the M102 debate

A catalog assembled by hand over 23 years, from a Paris rooftop, carries scars, and they are part of its charm. The site treats them honestly rather than smoothing them over:

• M40 is a double star. Messier went looking for a nebula Hevelius had reported near Megrez, found nothing but a faint pair of stars, and cataloged the pair anyway. Modern measurements show the two stars are unrelated, a chance alignment.
• M73 is four unrelated stars. A tiny Y-shaped knot that Messier described as a cluster containing nebulosity. Precise distances have since shown the four stars lie at different depths; there is no cluster and no nebulosity.
• M47 and M48 were lost for centuries. Sign errors and a 5-degree slip in Messier's recorded positions meant no object existed at either cataloged spot. The true identities (NGC 2422 and NGC 2548) were only pinned down in the 20th century, both puzzles fully settled in 1959. M91 stayed lost even longer, until a 1969 analysis showed Messier had measured it from the wrong reference galaxy.
• M102 may be a duplicate. Mechain reported it, then wrote a letter saying it had been a re-observation of M101. But Messier's handwritten position and description fit the Spindle Galaxy, NGC 5866, remarkably well. The literature has argued both ways for two centuries. This page follows the common modern practice of treating NGC 5866 as M102, and says so rather than pretending the question is closed.
• M45 has no NGC number. The Pleiades were too obviously a star cluster to make the New General Catalogue, so one of the sky's most famous objects has no NGC or IC number at all; Melotte 22 is its main alternate designation.

Object-by-object guides

Every object below gets the same honest treatment: what it is, who found it, the accepted distance, and how to find and see it, including the minimum equipment and the brightest sky (its Bortle class) in which it stays an easy catch. The star-hop directions assume you can point at the bright stars of the season; the constellation guides cover that first step. Photographs are NASA imagery; the eyepiece always shows less color and less nebulosity than any photo, and the guides say what you will actually see.

Common questions

What is the Messier catalog?

A list of 110 deep-sky objects compiled by the French comet hunter Charles Messier between 1758 and 1781, with seven historical additions completed in 1966. Messier recorded the fuzzy objects that could be mistaken for comets so he could ignore them, and his list of distractions turned out to be a nearly complete inventory of the northern sky's finest clusters, nebulae and galaxies.

How many Messier objects are there?

There are 110. Messier's final 1781 publication listed 103; historians later restored seven more objects (M104 through M110) that Messier and his collaborator Pierre Mechain had observed but never numbered, the last of them in 1966.

Can you see Messier objects without a telescope?

Yes. Eight of the 110 are routine naked-eye objects from a dark site, including the Pleiades, the Beehive Cluster, the Andromeda Galaxy and the Orion Nebula, and a few more, led by the Lagoon Nebula and the Triangulum Galaxy, are naked-eye stretch targets under excellent skies. Another 48 need nothing beyond ordinary binoculars; the rest require a telescope, though most are within reach of a small one.

What is the easiest Messier object to see?

The Pleiades (M45), an unmistakable naked-eye star cluster even from bright suburbs. After it, the Orion Nebula (M42), the Beehive (M44), the Andromeda Galaxy (M31) and the Hercules Cluster (M13) are the classic first deep-sky targets, and all five reward any instrument from binoculars up.

What is the hardest Messier object to see?

By common consent M74, a face-on spiral galaxy whose light is spread so thin that it vanishes in any light pollution or moonlight. The Little Dumbbell Nebula (M76) and the galaxy M98 are the other usual nominees. All three reward a genuinely dark sky and patience at low power.

What is a Messier marathon?

An attempt to observe all 110 objects in a single night. It is possible only around the March new moon, when the Sun sits in the one stretch of sky nearly empty of Messier objects, and a complete run is realistic only between about 20 and 40 degrees north latitude, under dark skies with clean horizons.

Why are there no far-southern objects in the catalog?

Messier observed from Paris, at 49 degrees north, so nothing in his catalog lies south of about declination -35. The great southern showpieces such as Omega Centauri and the Carina Nebula belong to later lists, chiefly the 109-object Caldwell catalog.

What is the difference between M numbers and NGC numbers?

M numbers are the catalog's 110 entries. NGC numbers come from the New General Catalogue of 1888, which lists 7,840 objects; most Messier objects also carry one. The exceptions: M24 and M25 have Index Catalogue numbers instead (IC 4715 and IC 4725), while M40, a double star, and M45, the Pleiades, have neither.

Are the Messier objects numbered in order across the sky?

No. The numbers follow the order in which Messier logged the objects over 23 years, so consecutive numbers can sit on opposite sides of the sky. That is also why marathon observers work from a custom sequence rather than counting from M1 to M110.

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