Antennae Galaxies

The Antennae Galaxies (also known as NGC 4038/NGC 4039 or Caldwell 60/Caldwell 61) are a pair of interacting galaxies in the constellation Corvus. They are currently going through a starburst phase, in which the collision of clouds of gas and dust, with entangled magnetic fields, causes rapid star formation. They were discovered by William Herschel in 1785.

The Antennae Galaxies are undergoing a galactic collision. These interacting galaxies are located 0.25° north of 31 Crateris and 3.25° southwest of Gamma Corvi.

Located in the NGC 4038 group with five other galaxies, these two galaxies are known as the Antennae Galaxies because the two long tails of stars, gas and dust ejected from the galaxies as a result of the collision resemble an insect's antennae.

The nuclei of the two galaxies are joining to become one giant galaxy. Most galaxies probably undergo at least one significant collision in their lifetimes. This might be the future of our Milky Way with a 50 percent chance of colliding with the Andromeda Galaxy. This collision and merger sequence (the Toomre sequence) for galaxy evolution was developed in part by successfully modeling the Antennae Galaxies' "antennae" in particular.

The Antennae galaxies also contain a relatively young collection of massive globular clusters that were possibly formed as a result of the collision between the two galaxies. The young age of these clusters is in contrast to the average age of most known globular clusters (which are around 12 billion years old), with the formation of the globulars likely originating from shockwaves, generated by the collision of the galaxies, compressing large, massive molecular clouds. The densest regions of the collapsing and compressing clouds are believed to be the birthplace of the clusters.

NGC 4038 has many Cepheid variables, around 53 of them.

Antennae Galaxies are widely accepted to be located at roughly 20 megaparsecs (70 million light-years) from Earth. However, a 2008 study stated that they are less remote from the Milky Way than previously thought—at 13.3 ± 1.0 megaparsec (43.4 ± 3.26 million light-years) based on photometry of the presumed tip of the red-giant branch, but an immediate paper later found three major issues regarding this estimate and considered it to be a probable misidentification of the tip of the red-giant branch. An average distance estimate of 22 ± 3 megaparsecs (71.8 ± 9.78 million light-years) has been also calculated based on observations of the Type Ia SN 2007sr in the southern tail using Las Campanas Observatory, the large-scale flow model, reanalyzing Hubble Space Telescope data in the Archive with an improved method, finding a fainter tip of the red-giant branch.

Four supernovae have been observed in NGC 4038.