NGC 4038. Caldwell 60 + 61. The Antennae

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NGC 4038 (on the center-left of the image, as well as its counterpart in this image, NGC 4039) has no less than eight different denominations. The most popular are NGC 4038 (9), Caldwell 60 (1), Arp 244 and The Antennae galaxies. They are a pair of interacting (colliding) spiral galaxies and the closest colliding pair to the Milky Way. This kind of galactic collisions usually triggers star birth. This is the reason for the strong blue hue on NGC 4038 (on the left). If some of the stars being generated are massive, their lifetime is short and they end up in colossal supernova explosions. In fact, five supernovae have been observed in these galaxies in the last 100 years. Another consequence of the collision is that huge numbers of globular clusters are generated. Although globular clusters are usually associated with old ages, the pressure of the colliding Interstellar Medium (ISM) accounts for the formation of large groups of close stars, originating star clusters.

Our milky Way and the Andromeda Galaxy (M31) also head on for a collision with each other in a few billion years. The appearance of this collision will, most probably, resemble the current Antennae galaxies.