Messier  

A text version of the Messier list is also available.

About the images

Most of the black & white images in this gallery are from the Digitized Sky Survey. Many of the objects are not nicely depicted in DSS since it's a survey and that some of the scanned plates are heavily underexposed etc., and therefore some of the images are not DSS-pictures. Most of the images are not to scale because of the range of different sizes of the Messier objects.

This gallery also uses fantastic color images by David Malin reproduced with kind permission by the photographer himself and the Anglo-Australian Observatory. These images are some of the best film based images ever made from ground based telescopes. David Malin is famous among astrophotographers for his beautiful images and brilliant and groundbreaking darkroom work. To see more images taken at AAO, please visit their homepage (or mirror site).

Other Messier galleries, images or catalogs

• Historical information at SEDS's Messier Catalog
• Chris Dolan's Listing of Messier objects
• Manchester Astronomical Society Messier Album
• UA Astronomy Messier Picture Gallery
• Astronomy Picture of the Day, Messier Objects
• METU's Messier Objects
• Bert Decker's Drawings of Messier Objects
• For the complete Digitized Sky Survey.

Help for the Messier Gallery

Other names

There are many catalogs other than the NGC/IC and Messier's catalog, and some objects have 30 or more names from different catalogs. A few of the more common alternative names for Messier objects are listed here. Many objects (especially in Messier's list) also have unofficial common names. Some are named after the discoverer, other for their shape or likeliness to something else.

Type

The following types are in use:

• OC: Open Cluster
  Open clusters are tight collections of stars in the Milky Way. The clusters in Messier's catalog are mostly bright and easy. The stars in these clusters were once formed together in giant clouds like the Orion Nebula (M42), and then continue together after the nebulosity has dispersed. Many clusters have nebulae associated with them. The difference from normal stars is that the stars in an OC stick together because of the gravity between them.
• GC: Globular Cluster
  Globular clusters can be seen as miniature galaxies, although some of them can be quite large and often resemble small dwarf galaxies. Globular clusters are actually small satellites to our Milky Way galaxy with millions of stars packed together in a tight ball. They are scattered around the main hub of the Milky Way in a halo (called the galactic halo) which is a sphere that extends roughly just beyond the main disk of the Milky Way.
• GX: Galaxy
  Galaxies are huge collections of stars, dust and gas rotating around a common center. There are many types. The main categories are spirals (S), barred spirals (SB), elliptic (E) and irregular (Ir).
• PN: Planetary Nebula
  Planetary nebulae (it's written "nebulae" in plural and "nebula" in singular form) are small bubbles of hot gas ejected from a central star. The gas once was a part or the star, but after turbulent times when the hydrogen in the central hydrogen-burning core ran short, the outer layers of the star was ejected and gas now moving outwards is heated by the hot exposed inner parts which is the remaining star. Because of this heat, the gas bubble radiates, and thus is visible to us in various colors. But after a relatively short time (in comparison to the full extent of a stars life) the heat from star declines and the gas dissipates and the gas bubble becomes invisible.
• BN: Bright Nebula
  Bright nebulae are huge collections of gas and dust which either is shining because of its "hot" temperature or it reflects light from the stars in the nebula. Therefore the two types, E (for emission) and R (for reflection). The third type is the supernova remnant (SNR) which are remnants from giant explosions where a star blew itself to pieces, leaving only a neutron star or a black hole in the center of an expanding shell of gas. The gas shell can either shine by emission (SNR-E) or reflection (of starlight from nearby stars) (SNR-R).
• DN: Dark Nebula
  Although none of the Messier objects are dark nebulae, I might mention one or two. They are non-illuminated dust and gas in the interstellar space which thus seem dark. Many dark nebulae are easily visible tracing the Milky Way in dark bands. We see dark nebulae because they block out starlight from the stars behind them.
• *2: Double Star
  All stars are born in giant gas clouds (like M42), and therefore some of them (or actually most) form in pairs. There can be more then two stars in a star system, and then we call them triple stars, quadruple or even multiple stars.
• *C: Star Cloud
  These are large collections of stars, and unlike clusters and double stars do not have gravitational bound members. They are only "lumps" in the Milky Way or merely optical illusions.

Constellation

The sky is divided into constellations. Stars appear to make out some formation in the sky, and these formations have been named by peoples of old. The western constellations are based primarily on Greek mythology, while other cultures have different constellations based on their own mythology or religion.

Num. *

Number of stars in the object. For open clusters this number is mostly inaccurate because many of the stars are too faint to be detected. But the number gives a measure of the clusters richness.

Inclination

The galaxies which appear as pancakes or close to it, are positioned in a certain inclination relative to our line of sight. An inclination of 1 indicate that we see straight onto the plane, while an inclination of 7 indicates that we are looking into the plane.

* magnitude

This is the magnitude of the central star in planetary nebulae or the magnitude for the brightest stars in clusters ("**") or the mean magnitude for the stars in the horizontal branch (a period in a stars life) in clusters ("HB").

Concentration

This is a number for the "compactness" of a globular cluster. 1 is most compact, 9 is most loose.

SB (Specific Brightness)

Indicates the brightness of a galaxy, that is the amount of light emmitted by it.

PA (Position Angle)

The angle in which the galaxy appears compared to celestial north (very close to Polaris). 0 indicates that the plane of the galaxy is parallel to the north/south direction, 90 indicates a galaxy turned horizontally and so on. PA is always between 0 and 179, because 180 would imply the same as 0.

Magnitude

The apparent magnitude of the object. Each magnitude is about 2.5 times fainter than the previous, so that mag 4 is 2.5 times brighter than mag 5.

RA (Right Ascension)

The time it would take from passing of the meridian through a fixed telescope (with the right declination) till when the object would appear in the telescope. No more than 24 hours. Given in hours (h), minutes (m) and seconds (s).

Dec (Declination)

Declination is the angle above or below the celestial equator, and thus goes from -90 to +90 degrees.

Distance

The distance is given in light years (ly) which is the distance light travels in on year in vacuum. 1 Mly = 1,000 kly = 1,000,000 ly.

Dimension

Dimensions are given in arc minutes (') or arc seconds ("). 1 degree = 60 arc minutes = 3600 arc seconds. Comparable with the time intervals in a clock face.