Leo Triplet

The Leo Triplet (also known as the M66 Group) is a small group of galaxies about 35 million light-years away[5] in the constellation Leo. This galaxy group consists of the spiral galaxies M65, M66, and NGC 3628.

Leo Triplet
The Leo Triplet, with M65 (right top), M66 (right bottom) and
NGC 3628 (left). North is to the left.
Observation data (Epoch J2000)
Right ascension11h 17m[1][2]
Declination+13° 25′[1][2]
Brightest memberM66[1][2]
Number of galaxies3-5[1][2][3]
Other designations
M66 Group, Arp 317,[4] LGG 231,[1]
NOGG P1 533,[2] NOGG P2 543[2]


The table below lists galaxies that have been consistently identified as group members in the Nearby Galaxies Catalog,[3] the Lyons Groups of Galaxies (LGG) Catalog,[1] and the group lists created from the Nearby Optical Galaxy sample of Giuricin et al.[2]

Member list

Members of the Leo Triplet
Name Type[6] R.A. (J2000)[6] Dec. (J2000)[6] Redshift (km/s)[6] Apparent Magnitude[6]
M65 SAB(rs)a  11h 18m 56.0s +13° 05′ 32″ 807 ± 3 10.3
M66 SAB(s)b  11h 20m 15.0s +12° 59′ 30″ 727 ± 3 9.7
NGC 3628 SAb pec  11h 20m 17.0s +13° 35′ 23″ 843 ± 1 9.4

Additionally, some of the references cited above indicate that one or two other nearby galaxies may be group members. NGC 3593 is frequently but not consistently identified as a member of this group.

Nearby groups

The M96 Group is located physically near the Leo Triplet.[7] These two groups may actually be separate parts of a much larger group,[7] and some group identification algorithms actually identify the Leo Triplet as part of the M96 Group.[2][8]


VST's view of the Leo Triplet and beyond

VST's view of the Leo Triplet and beyond.[9] This image hints at the power of the ESO's VST and OmegaCAM for surveying the extragalactic Universe.

Leo Triplet amateur image

Leo Triplet amateur image

See also


  1. ^ a b c d e f A. Garcia (1993). "General study of group membership. II – Determination of nearby groups". Astronomy and Astrophysics Supplement. 100: 47–90. Bibcode:1993A&AS..100...47G.
  2. ^ a b c d e f g h G. Giuricin; C. Marinoni; L. Ceriani; A. Pisani (2000). "Nearby Optical Galaxies: Selection of the Sample and Identification of Groups". Astrophysical Journal. 543 (1): 178–194. arXiv:astro-ph/0001140. Bibcode:2000ApJ...543..178G. doi:10.1086/317070.
  3. ^ a b R. B. Tully (1988). Nearby Galaxies Catalog. Cambridge: Cambridge University Press. ISBN 0-521-35299-1.
  4. ^ H. Arp (1966). "Atlas of Peculiar Galaxies". Astrophysical Journal Supplement. 14: 1–20. Bibcode:1966ApJS...14....1A. doi:10.1086/190147.
  5. ^ VST Looks at the Leo Triplet — and Beyond
  6. ^ a b c d e "NASA/IPAC Extragalactic Database". Results for various galaxies. Retrieved 2006-10-24.
  7. ^ a b L. Ferrarese, H. C. Ford, J. Huchra, R. C. Kennicutt Jr., J. R. Mould, S. Sakai, W. L. Freedman, P. B. Stetson, B. F. Madore, B. K. Gibson, J. A. Graham, S. M. Hughes, G. D. Illingworth, D. D. Kelson, L. Macri, K. Sebo, N. A. Silbermann (2000). "A Database of Cepheid Distance Moduli and Tip of the Red Giant Branch, Globular Cluster Luminosity Function, Planetary Nebula Luminosity Function, and Surface Brightness Fluctuation Data Useful for Distance Determinations". Astrophysical Journal Supplement. 128 (2): 431–459. arXiv:astro-ph/9910501. Bibcode:2000ApJS..128..431F. doi:10.1086/313391.CS1 maint: Multiple names: authors list (link)
  8. ^ P. Fouque, E. Gourgoulhon, P. Chamaraux, G. Paturel; Gourgoulhon; Chamaraux; Paturel (1992). "Groups of galaxies within 80 Mpc. II – The catalogue of groups and group members". Astronomy and Astrophysics Supplement. 93: 211–233. Bibcode:1992A&AS...93..211F.CS1 maint: Multiple names: authors list (link)
  9. ^ "VST Looks at the Leo Triplet — and Beyond". ESO Photo Release. Retrieved 27 July 2011.

External links

Coordinates: Sky map 11h 17m 00s, +13° 25′ 00″

Atlas of Peculiar Galaxies

The Atlas of Peculiar Galaxies is a catalog of peculiar galaxies produced by Halton Arp in 1966. A total of 338 galaxies are presented in the atlas, which was originally published in 1966 by the California Institute of Technology. The primary goal of the catalog was to present photographs of examples of the different kinds of peculiar structures found among galaxies.

Leo (constellation)

Leo is one of the constellations of the zodiac, lying between Cancer the crab to the west and Virgo the maiden to the east. Its name is Latin for lion, and to the ancient Greeks represented the Nemean Lion killed by the mythical Greek hero Heracles meaning 'Glory of Hera' (known to the ancient Romans as Hercules) as one of his twelve labors. Its symbol is (Unicode ♌). One of the 48 constellations described by the 2nd-century astronomer Ptolemy, Leo remains one of the 88 modern constellations today, and one of the most easily recognizable due to its many bright stars and a distinctive shape that is reminiscent of the crouching lion it depicts. The lion's mane and shoulders also form an asterism known as "The Sickle," which to modern observers may resemble a backwards "question mark."

List of galaxy groups and clusters

This page lists some galaxy groups and galaxy clusters.

Defining the limits of galaxy clusters is imprecise as many clusters are still forming. In particular, clusters close to the Milky Way tend to be classified as galaxy clusters even when they are much smaller than more distant clusters.

M96 Group

The M96 Group (also known as the Leo I Group) is a group of galaxies in the constellation Leo. This group contains between 8 and 24 galaxies, including three Messier objects. The group is one of many groups that lies within the Virgo Supercluster (the combined Local Group and Virgo cluster).

Messier 65

Messier 65 (also known as NGC 3623) is an intermediate spiral galaxy about 35 million light-years away in the constellation Leo. It was discovered by Charles Messier in 1780. Along with M66 and NGC 3628, M65 forms the Leo Triplet, a small group of galaxies.

Messier 66

Messier 66 or M66, also known as NGC 3627, is an intermediate spiral galaxy in the equatorial constellation of Leo. It was discovered by French astronomer Charles Messier on March 1, 1780, who described it as "very long and very faint". This galaxy is a member of a small group of galaxies that includes M65 and NGC 3628, known as the Leo Triplet, or the M66 Group. M65 and M66 make a popular pair for observers, being separated by only 20′.M66 has a morphological classification of SABb, indicating a spiral shape with a weak bar feature and loosely wound arms. The isophotal axis ratio is 0.32, indicating that it is being viewed at an angle. M66 is receding from us with a heliocentric radial velocity of 696.3±12.7 km/s. It lies 31 million light-years away and is about 95 thousand light-years across with striking dust lanes and bright star clusters along sweeping spiral arms. As of 2018, five supernovae have been observed in M66: SN 2016cok, 2009hd, 1997bs, 1989B, and 1973R.Gravitational interaction from its past encounter with neighboring NGC 3628 has resulted in an extremely high central mass concentration; a high molecular to atomic mass ratio; and a resolved non-rotating clump of H I material apparently removed from one of the spiral arms. The latter feature shows up visually as an extremely prominent and unusual spiral arm and dust lane structures as originally noted in the Atlas of Peculiar Galaxies.

Messier object

The Messier objects are a set of 110 astronomical objects cataloged by the French astronomer Charles Messier in his Catalogue des Nébuleuses et des Amas d'Étoiles ("Catalogue of Nebulae and Star Clusters").

Because Messier was interested in finding only comets, he created a list of non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as the Messier catalogue. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier number.

The catalogue includes some astronomical objects that can be observed from Earth's Northern Hemisphere such as deep-sky objects, a characteristic which makes the Messier objects extremely popular targets for amateur astronomers.A preliminary version first appeared in the Memoirs of the French Academy of Sciences in 1771,

and the last item was added in 1966 by Kenneth Glyn Jones, based on Messier's observations.

The first version of Messier's catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. In addition to his own discoveries, this version included objects previously observed by other astronomers, with only 17 of the 45 objects being Messier's.

By 1780 the catalogue had increased to 80 objects. The final version of the catalogue containing 103 objects was published in 1781 in the Connaissance des Temps for the year 1784.

However, due to what was thought for a long time to be the incorrect addition of Messier 102, the total number remained 102. Other astronomers, using side notes in Messier's texts, eventually filled out the list up to 110 objects.The catalogue consists of a diverse range of astronomical objects, ranging from star clusters and nebulae to galaxies. For example, Messier 1 is a supernova remnant, known as the Crab Nebula, and the great spiral Andromeda Galaxy is M31. Many further inclusions followed in the next century when the first addition came from Nicolas Camille Flammarion in 1921, who added Messier 104 after finding Messier's side note in his 1781 edition exemplar of the catalogue. M105 to M107 were added by Helen Sawyer Hogg in 1947, M108 and M109 by Owen Gingerich in 1960, and M110 by Kenneth Glyn Jones in 1967.

NGC 3593

NGC 3593 is a lenticular galaxy located in the constellation Leo. It has a morphological classification of SA(s)0/a, which indicates it is a lenticular galaxy of the pure spiral type. This is a starburst galaxy, which means it is forming new stars at a high rate. This is occurring in a band of gas surrounding the central nucleus. There is a single arm, which spirals outward from this ring. It is frequently but not consistently identified as a member of the Leo Triplet group.This galaxy is known to contain two counter-rotating populations of stars. That is, one set of stars is rotating in the opposite direction with respect to the other. One means for this to occur is by acquiring gas from an external source, which then undergoes star formation. An alternative is by a merger with a second galaxy. Neither scenario has been ruled out. The age of the lower mass, counter-rotating population is younger by about 1.6 ± 0.8 Gyr than the primary star population of the galaxy.

NGC 3628

'NGC 3628, also known as the Hamburger Galaxy or Mahasin's Galaxy, is an unbarred spiral galaxy about 35 million light-years away in the constellation Leo. It was discovered by William Herschel in 1784. It has an approximately 300,000 light-years long tidal tail. Along with M65 and M66, NGC 3628 forms the Leo Triplet, a small group of galaxies. Its most conspicuous feature is the broad and obscuring band of dust located along the outer edge of its spiral arms, effectively transecting the galaxy to the view from Earth.

Due to the presence of an x-shaped bulge, visible in multiple wavelengths, it has been argued that NGC 3628 is instead a barred spiral galaxy with the bar seen end-on. Simulations have shown that bars often form in disk galaxies during interactions and mergers, and NGC 3628 is known to be interacting with its two large neighbors.

NGC 5866 Group

The NGC 5866 Group is a small group of galaxies located in the constellation Draco. The group is named after NGC 5866, the galaxy with the highest apparent magnitude in the group, although some galaxy group catalogs list NGC 5907 as the brightest member.

Seyfert galaxy

Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars. They have quasar-like nuclei (very luminous, distant and bright sources of electromagnetic radiation) with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, but unlike quasars, their host galaxies are clearly detectable.Seyfert galaxies account for about 10% of all galaxies and are some of the most intensely studied objects in astronomy, as they are thought to be powered by the same phenomena that occur in quasars, although they are closer and less luminous than quasars. These galaxies have supermassive black holes at their centers which are surrounded by accretion discs of in-falling material. The accretion discs are believed to be the source of the observed ultraviolet radiation. Ultraviolet emission and absorption lines provide the best diagnostics for the composition of the surrounding material.Seen in visible light, most Seyfert galaxies look like normal spiral galaxies, but when studied under other wavelengths, it becomes clear that the luminosity of their cores is of comparable intensity to the luminosity of whole galaxies the size of the Milky Way.Seyfert galaxies are named after Carl Seyfert, who first described this class in 1943.

VLT Survey Telescope

The VLT Survey Telescope (VST) is the latest telescope to be added to ESO’s Paranal Observatory in the Atacama Desert of northern Chile. It is housed in an enclosure immediately adjacent to the four Very Large Telescope (VLT) Unit Telescopes on the summit of Cerro Paranal. The VST is a wide-field survey telescope with a field of view twice as broad as the full Moon. It is the largest telescope in the world designed to exclusively survey the sky in visible light.The VST program is a cooperation between the Osservatorio Astronomico di Capodimonte (OAC), Naples, Italy, and the European Southern Observatory (ESO) that began in 1997. The OAC is one of the institute members of Istituto Nazionale di AstroFisica (INAF), which created a separate institute for the coordination of both technological and scientific aspects of the project, named Centro VST a Napoli (VSTceN). VSTcen was founded and directed by Prof. Massimo Capaccioli of the VST project, and hosted at the OAC. ESO and VSTceN collaborated in the commission phase, while ESO was responsible for the civil engineering works and the dome on site. The telescope has now started observations and ESO is solely responsible for managing its operations and maintenance.

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