The Antennae Galaxies, also known as the Ringtail Galaxy or Arp 244, are a pair of colliding galaxies located in Corvus constellation. The interacting spiral galaxies have the designations NGC 4038 and NGC 4039 in the New General Catalogue.
The galaxy collision resembles an insect’s antennae, which is how the pair got the name. The “antennae” are formed by two long tails of stars, dust and gas expelled from the galaxies as a result of their interaction.
The colliding galaxies reveal a likely future of the Milky Way when it collides with the neighbouring Andromeda Galaxy (Messier 31) in several billion years.
The Antennae Galaxies are one of the youngest examples of colliding galaxies, as well as one of the nearest pairs of interacting galaxies to Earth.
The Antennae Galaxies are going through a phase of intense starburst activity as their colliding clouds of dust and gas compress massive molecular clouds and cause rapid formation of millions of new stars.
Some of the newly formed stars are gravitationally bound and form massive clusters.
More than a thousand bright clusters consisting of newly formed stars have recently been discovered in the Ringtail Galaxy by astronomers.
The brightest and most compact starburst regions contain super star clusters. Billions of stars will be formed before the galactic collision is over.
The Antennae Galaxies’ nuclei are in the process of joining to form a single giant galaxy. This will happen within the next 400 million years.
Simulations of the galactic collision indicate that as the galaxies’ nuclei join to form a single core, the two galaxies will eventually form a single giant elliptical galaxy.
The Antennae Galaxies lie at a distance of 45 million light years from Earth.
NGC 4038 and NGC 4039 were two separate galaxies some 1.2 billion years ago. NGC 4039 was a spiral galaxy and the larger of the two, while NGC 4038 was a barred spiral galaxy.
The two galaxies started approaching each other roughly 900 million years ago. At this point, the pair appeared similar to the colliding spiral galaxies NGC 2207 and IC 2163, located in Canis Major constellation.
The Antennae Galaxies are believed to have passed through each other about 600 million years ago, when they may have appeared similar to the Mice Galaxies (NGC 4676), a pair of interacting spiral galaxies lying in the direction of the constellation Coma Berenices.
300 million years later, the stars in both galaxies started being released into intergalactic space. As a result, there are now two streamers of expelled stars extending far beyond NGC 4038 and NGC 4039, giving the pair the appearance of the antennae.
FACTS
The Antennae Galaxies were discovered by William Herschel in 1785.
NGC 4038 and NGC 4039 are passing through each other at a very high speed, at hundreds of kilometres per second. The reason why the galactic merger is taking hundreds of millions of years to complete is the enormous size of the galaxies.
The galaxies’ tidal tails that have earned them the name Antennae were formed 200 to 300 million years ago, during the galaxies’ first encounter. As the galaxies collided and passed through each other, some of their stars, dust and gas were drawn out into long tails of material. The two streamers will eventually either fall back into the newly formed elliptical galaxy or be lost to space.
The Antennae Galaxies are members of the NGC 4038 Group along with five other galaxies.
Two supernovae were discovered in the Antennae Galaxies in the last decade: SN 2004GT in 2004 and SN 2007sr in 2007.
Most of the super star clusters formed in the Antennae will disperse within the first 10 million years. Astronomers have predicted that only 10 percent of these clusters will last longer. Roughly a hundred of the most massive ones will survive to eventually form regular globular clusters, similar to those found in our galaxy, the Milky Way.
A Chandra X-ray Observatory study of the Antennae Galaxies revealed that they contain considerable amounts of elements necessary for the formation of habitable planets, including magnesium, neon, and silicon.
The distance between the galaxies’ centres is estimated to be around 30,000 light years. The nuclei of NGC 4038 and NGC 4039 are believed to contain mostly old stars.
Antennae Galaxies – NGC 4038 and NGC 4039
Type: SB(s)m pec (NGC 4038), SA(s)m pec (NGC 4039)
Constellation: Corvus
Coordinates:
NGC 4038 – 12h 01m 53s (right ascension), -18°52’10” (declination)
NGC 4039 – 12h 01m 53.6s (right ascension), -18°53’11” (declination)
Distance: 45 million light years
Apparent magnitude: 11.2 (NGC 4038), 11.1 (NGC 4039)
Apparent dimensions: 5′.2 × 3′.1 (NGC 4038), 3′.1 × 1′.6 (NGC 4039)
Designations: Antennae Galaxies, Ringtail Galaxy, Arp 244, NGC 2038, NGC 2039, Caldwell 60, Caldwell 61, PCG 37967, PGC 37969
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