The Meathook Galaxy is an intermediate spiral galaxy located approximately 50 million light-years away in the southern constellation of Volans (the Flying Fish). Also known as the Cobra and Mouse, the galaxy has two designations in the New General Catalogue. Its southwestern part is catalogued as NGC 2442 and its northeastern part is listed as NGC 2443. The galaxy has an apparent magnitude of 11.2 and an apparent size of 5.5 by 4.9 arcminutes.
Known for its double-hook shape, the Meathook Galaxy is about 160,000 light years across. The unusual curve of the galaxy’s spiral arm and its hook-like appearance are likely the product of a collision with another galaxy that occurred around 200 million years ago. The gravitational interaction between the two galaxies drew out the spiral arms of NGC 2442.
The other galaxy was identified as AM 0738-692 (PGC 21457, ESO 59-11), which appears close to NGC 2442 in the sky, in 1996. While studying star formation and kinematics in the Meathook Galaxy, J. Christopher Mihos of Johns Hopkins University in Baltimore and Gregory D. Bothun of the University of Oregon found evidence for strong noncircular motion along the galaxy’s northern arm that coincided with active star forming regions. This, combined with the presence of the perturbed companion and the strong asymmetries in NGC 2442, indicated a close interaction.
Meathook Galaxy (NGC 2442 and NGC 2443), image credit: SSRO/PROMPT and NOIRLab/NSF/AURA (CC BY 4.0)
As a result of the close encounter, star forming activity has been redistributed throughout the Meathook Galaxy’s disk. The regions of the dark dust lanes and the most intense star formation are associated with strong shocks along the tidally distorted northern arm. Similarly, the smaller AM 0738-692 has a disturbed morphology and its outer arms look like tidal tails ripped out during the encounter.
Mihos and Bothun proposed that NGC 2442 will eventually recover from the tidal encounter and that it will experience another encounter. It will ultimately merge into a larger galaxy with AM 0738-692 in a few billion years.
NGC 2442 is a LINER galaxy. It has a low-ionization nuclear emission-line region (LINER), a type of galactic nucleus that shows spectral line emissions from neutral or weakly ionized atoms. The spectral emission may indicate the presence of an active galactic nucleus (AGN) with a central supermassive black hole, or it may be powered by star-forming regions.
A 2021 study confirmed that the galaxy has an active galactic nucleus. A team led by Patricia da Silva of the Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Departamento de Astronomia, Universidade de São Paulo, Brazil, found that the galaxy’s nucleus was associated with an obscured compact hard X-ray source and that the central regions were populated only by old stellar populations, with an estimated age of 10 billion years. The astronomers found no evidence of recent star formation in the region after analysing data obtained with the Gemini Multi-Object Spectrograph (GMOS), the Chandra X-ray Observatory, XMM Newton, NuSTAR, and the Hubble Space Telescope (HST).
In 2001, a team of astronomers led by S. D. Ryder of the Anglo-Australian Observatory in Australia reported the discovery of an intergalactic gas cloud devoid of stars, associated with NGC 2442. The cloud was detected during the H I Parkes All-Sky Survey (HIPASS) and catalogued as HIPASS J0731-69. The diffuse gas does not have an optical counterpart. If it was once part of the Meathook Galaxy, it may have been ripped out in a recent tidal encounter with a relatively massive companion. The bulk of the gas cloud lies at a separation of almost 40 minutes of arc from NGC 2442.
This picture of the Meathook Galaxy (NGC 2442) was taken by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla, Chile. It shows a much broader view than the Hubble image, although less detailed. This view includes the whole galaxy and the surrounding sky, and clearly shows the asymmetric spiral arms. The longer of the two arms has intense star formation, which is visible here as a pink glow: this is due to the radiation of young stars ionising the gas they form from. The asymmetric shape and star formation are both thought to be caused by tidal disruptions from a near-miss with another galaxy at some point in its history. Image credit: ESO (European Southern Observatory) (CC BY 3.0)
Facts
The Meathook Galaxy was discovered by the English astronomer Sir John Herschel on December 23, 1834. The asymmetrical galaxy has a double listing in the New General Catalogue because Herschel initially saw its northeastern and southwestern parts as two faint nebulae that appeared to be separated by a stellar middle. He described the object as a “double nebula.” Even though later observations showed that the two nebulous objects were in fact a single large object, the Danish astronomer John Louis Emil Dreyer, who compiled the New General Catalogue in 1888, kept the original double listing.
The fainter elliptical galaxy NGC 2434 appears in the same area of the sky as the Meathook Galaxy. It has an apparent magnitude of 11.5 and is 2.5 by 2.5 arcminutes across. John Herschel discovered it on the same evening as NGC 2442 and NGC 2443. The galaxy lies approximately 88 million light years (27 Mpc) away.
The Meathook Galaxy, AM 0738-692, and NGC 2434 may be members of a loose galaxy group.
The Meathook Galaxy, NGC 2434 and PGC 21457 (AM 0738-692), image credit: ESO/Digitized Sky Survey 2 (CC BY 4.0)
The Meathook Galaxy hosted two or three supernovae in the recent decades. SN 1999ga was a type II supernova that shone at magnitude 18 and was discovered in November 1999. SN 2015F was classified as a type Ia supernova. It had an apparent magnitude of 16.8 and peaked at magnitude 12.9. It was detected in March 2015.
AT 2016jbu (Gaia16cfr) was a supernova impostor event that occurred in December 2016. It reached a visual magnitude of 19.3. A 2022 study suggested that it may have been in fact a real supernova.
This image from the NASA/ESA Hubble Space Telescope features the spectacular galaxy NGC 2442. This galaxy was host to a supernova event, known as SN2015F, that was created by a white dwarf star. The white dwarf was part of a binary star system and syphoned mass from its companion, eventually becoming too greedy and taking on more than it could handle. This unbalanced the star and triggered runaway nuclear fusion that eventually led to a spectacular supernova. SN2015F was spotted in March 2015 in the galaxy named NGC 2442, nicknamed the Meathook Galaxy owing to its extremely asymmetrical and irregular shape. The supernova shone brightly for quite some time and was easily visible from Earth through even a small telescope until later that summer. Credit: European Space Agency (ESA) (CC BY 4.0)
Location
The Meathook Galaxy lies in the far southern sky, in the faint constellation of Volans. It appears near the midpoint of the imaginary line connecting Epsilon and Gamma2 Volantis.
The constellation figure of the Flying Fish lies near the Diamond Cross and the False Cross, two bright southern asterisms that are sometimes mistaken for the brighter Southern Cross. The Diamond Cross is formed by Miaplacidus (Beta Carinae) with Theta, Upsilon and Omega Carinae, and the brighter False Cross by Avior (Epsilon Carinae), Aspidiske (Iota Carinae), Alsephina (Delta Velorum), and Markeb (Kappa Velorum). Volans appears close to Miaplacidus, the second brightest star in Carina.
The location of the Meathook Galaxy (NGC 2442), image: Stellarium
At declination -69° 32’, the Meathook Galaxy is visible from locations south of the latitude 20° N. It stays below the horizon for most of the northern hemisphere and is best seen from locations south of the equator. It never rises very high above the horizon for observers in the northern tropical latitudes.
The best time of the year to observe the Meathook Galaxy and other deep sky objects in Volans is during the month of February, when the constellation appears higher above the horizon in the evening sky.
Meathook Galaxy – NGC 2442 and NGC 2443
| Constellation | Volans |
| Object type | Intermediate spiral galaxy |
| Morphological type | SAB(s)bc pec |
| Right ascension | 07h 36m 23.7700545576 s |
| Declination | −69° 31′ 50.997856332″ |
| Apparent magnitude | 11.2 |
| Apparent size | 5’.5 x 4’.9 |
| Distance | 50 million light-years (15.33 megaparsecs) |
| Redshift | 1,466 ± 5 km/s |
| Size | 160,000 light-years (48,940 parsecs) |
| Names and designations | Meathook Galaxy, Cobra and Mouse, NGC 2442 and NGC 2443, PGC 21373, LEDA 21373, ESO 59-8, ESO-LV 59-0080, AM 0736-692, PMN J0736-6931, HIPASS J0736-69, PSCz P07365-6924, SGC 073633-6925.0, 6dFGS gJ073623.8-693151, IRAS 07365-6924, IRAS F07365-6924, 2MASX J07362384-6931509, Gaia DR3 5267697094131487488 |
Images
This picture of the Meathook Galaxy (NGC 2442) was taken by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla, Chile. Credit: ESO (CC BY 3.0)
The distorted galaxy NGC 2442, also known as the Meathook Galaxy, is located some 50 million light-years away in the constellation of Volans (the Flying Fish). The galaxy is 75,000 light-years wide and features two dusty spiral arms extending from a pronounced central bar that give it a hook-like appearance, hence its nickname. The galaxy’s distorted shape is most likely the result of a close encounter with a smaller, unseen galaxy. This image is based on data acquired with the 1.5-metre Danish telescope at ESO’s La Silla Observatory in Chile, through three filters (B: 250 s, V: 187 s, R: 150 s). Image credit: ESO/IDA/Danish 1.5 m/R. Gendler, J.-E. Ovaldsen, C. C. Thöne and C. Féron (CC BY 4.0)
This close-up Hubble view of the Meathook Galaxy (NGC 2442) focuses on the more compact of its two asymmetric spiral arms as well as the central regions. The spiral arm was the location of a supernova that occurred in 1999. These Hubble observations were made in 2006 in order to study the aftermath of this supernova. Ground-based data from MPG/ESO 2.2-metre telescope were used to fill out parts of the edges of this image. Image credit: NASA and ESA (CC BY 4.0)