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NGC 6872: Condor Galaxy

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NGC 6872, also known as the Condor Galaxy, is a massive barred spiral galaxy located in the southern constellation Pavo.

The galaxy has a distinct shape of the integral sign. It has an apparent visual magnitude of 12.7 and is approximately 220 million light years distant from Earth. The galaxy is currently in the process of interacting with a lenticular galaxy, IC 4970.

The smaller IC 4970 – only a fifth the size of its larger neighbour – has an apparent magnitude of 14.7. It is located 1.1 arcminutes to the north of NGC 6872.

In January 2013, NASA said that NGC 6872 was one of the largest spiral galaxies ever discovered. The galaxy spans more than six minutes of arc in the sky and is about 522,000 light years across, which makes it about five times the size of our galaxy, the Milky Way. It contains anywhere between 500 billion to 2 trillion stars.

The Condor Galaxy contains a large number of star clusters. Most of the young clusters in the galaxy are less than 100 million years old and lie in the outer region of the galactic disk, in the tidal tails. The galaxy’s northern tail produces new stars at about five times the rate of the galaxy’s main body and at twice the rate of the southern tail.

colliding galaxies,galaxy collision,interacting galaxies

NGC 6872 and IC 4970 – This composite image of data from three different telescopes shows an ongoing collision between two galaxies, NGC 6872 and IC 4970. X-ray data from NASA’s Chandra X-ray Observatory is shown in purple, while Spitzer Space Telescope’s infrared data is red and optical data from ESO’s Very Large Telescope (VLT) is colored red, green and blue. Astronomers think that supermassive black holes exist at the center of most galaxies. Not only do the galaxies and black holes seem to co-exist, they are apparently inextricably linked in their evolution. To better understand this symbiotic relationship, scientists have turned to rapidly growing black holes — so-called active galactic nucleus (AGN) — to study how they are affected by their galactic environments. The latest data from Chandra and Spitzer show that IC 4970, the small galaxy at the top of the image, contains an AGN, but one that is heavily cocooned in gas and dust. This means in optical light telescopes, like the VLT, there is little to see. X-rays and infrared light, however, can penetrate this veil of material and reveal the light show that is generated as material heats up before falling onto the black hole (seen as a bright point-like source). Despite this obscuring gas and dust around IC 4970, the Chandra data suggest that there is not enough hot gas in IC 4970 to fuel the growth of the AGN. Where, then, does the food supply for this black hole come from? The answer lies with its partner galaxy, NGC 6872. These two galaxies are in the process of undergoing a collision, and the gravitational attraction from IC 4970 has likely pulled over some of NGC 6872’s deep reservoir of cold gas (seen prominently in the Spitzer data), providing a new fuel supply to power the giant black hole. Image: NASA, CXC, SAO, M.Machacek

IC 4970 has an active galactic nucleus (AGN), but the nucleus is clouded by dust and gas and can only be seen in X-rays and infrared light.

The galaxy’s black hole is likely fuelled by the gas from the larger galaxy, NGC 6872, as IC 4970 is not believed to have a sufficient supply of hot gas to fuel the central giant black hole.

The two galaxies had their closest encounter about 130 million years ago, which triggered a wave of star formation in the region along the larger galaxy’s spiral arms. At the time of the encounter, IC 4970 followed the path near the plane of NGC 6872’s spiral disk, following the direction in which it rotates.

One of the spiral arms of NGC 6872 in particular appears disturbed as a result of the collision and the smaller galaxy passing through it. The area contains a number of star forming regions.

There is another galaxy in the vicinity of NGC 6872, the elliptical galaxy NGC 6876, the brightest member of a nearby galaxy group. The galaxy was first discovered by the English astronomer John Herschel on June 27, 1835. It is located about 8 minutes of arc to the southeast of NGC 6872. The galaxy is believed to contain a binary black hole. It has a visual magnitude of 10.7.

An X-ray trail more than 100 kpc long was discovered between the two galaxies – NGC 6876 and NGC 6872 – in 2005.

NGC 6872
Type: SAB(rs)c
Coordinates: 20h16m56.5s (right ascension), -70°46’06” (declination)
Redshift: 4560 ± 30 km/s
Apparent dimensions: 6′.0 × 1′.7

IC 4970
Type: SA 0- pec
Coordinates: 20h16m57.1s (right ascension), -70°44’58” (declination)
Redshift: 4720 ± 40
Apparent dimensions: 0′.7 × 0′.2

NGC 6876
Type: E3
Coordinates: 20h18m19.60s (right ascension), -70°51’36.0” (declination)
Redshift: 3836
Apparent dimensions: 3.388×2.951′