Caldwell 60/61

Better known as the Antennae galaxies, Caldwell 60 and 61 are a pair of interacting spiral galaxies.


65 million light-years

Apparent Magnitude

10.5 and 11.0



object type

Spiral Galaxies

This new NASA Hubble Space Telescope image of the Antennae galaxies is the sharpest yet of this merging pair of galaxies. During the course of the collision, billions of stars will be formed. The brightest and most compact of these star birth regions are called super star clusters. The new image allows astronomers to better distinguish between the stars and super star clusters created in the collision of two spiral galaxies.
ESA/Hubble & NASA

This Hubble image shows two galaxies locked in a fateful embrace. Caldwell 60 (NGC 4038) and Caldwell 61 (NGC 4039) are known as the Ringtail or Antennae galaxies. At one time they were normal, sedate spiral galaxies similar to the Milky Way, but this galactic pair has spent the past few hundred million years sparring. This violent clash has ripped stars from their host galaxies to form a streaming arc between the two combatants. Wide-field views of the duo reveal long streamers of stars extending outward into space like a set of antennae, giving the duo their common nickname.

A ground-based telescopic view on the left shows the long tails of the Antennae galaxies. On the right, a natural-color image taken by Hubble in 1996 shows the respective cores of the twin galaxies (the orange blobs) crisscrossed by filaments of dark dust. A wide band of chaotic dust, called the overlap region, stretches between the cores of the two galaxies.
Brad Whitmore (STScI) and NASA

Hubble has targeted the Antennae galaxies multiple times over the years. Signs of chaos are obvious in this image released in 2013, which combines ultraviolet, visible, and infrared observations from Hubble’s Wide Field Camera 3 along with some previous observations from the Advanced Camera for Surveys. Blossoming clouds of pink and red gas cradle flashes of blue where new stars have just formed. Dark streaks of dust, pulled from the individual galaxies, sweep through and obscure vast parts of the scene.

Hubble’s observations have uncovered over a thousand bright, young star clusters bursting to life as a result of the head-on wreck. The sweeping spiral-like patterns, traced by these bright blue star clusters, show the result of a firestorm of star birth activity triggered by the collision. The extraordinary rate of star formation in the Antennae galaxies is known as a starburst, a period in which all of the gas within the galaxies is being used to form stars. Eventually this stellar inferno will burn itself out and the galaxies will settle down. The galactic cores will coalesce, and the once-separate galaxies will merge into one large elliptical galaxy.

The Antennae galaxies were discovered by astronomer William Herschel in 1785. They are located about 65 million light-years away in the Corvus constellation, best seen in autumn skies in the Southern Hemisphere but also visible in the springtime from the Northern Hemisphere. The galaxies have magnitudes of approximately 10.5 and 11, so a moderate to large telescope and dark skies are needed for optimal viewing. Even with a large telescope the Antennae galaxies will most likely resemble a faint, hazy comma.

This star chart for Caldwells 60 & 61 represents the view from mid-northern latitudes for the given month and time.
Image courtesy of Stellarium


Elliptical Galaxy - A nearly featureless, spherical or football-shaped galaxy, typically lacking new star formation and often containing much older stars than those in spiral galaxies.

Magnitude - The brightness of an astronomical object, represented by a number; bright objects have low numbers on the magnitude scale, while dim objects have high numbers.

Spiral Galaxy - A galaxy characterized by its spiral structure, with star-filled arms that extend out from the center of the galaxy and host regions of star formation.

Explore Hubble's Caldwell Catalog

The following pages contain some of Hubble’s best images of Caldwell objects.

Stars with four diffraction spikes dot the scene against a black backdrop.

Caldwell 1

Also known as NGC 188, this group of stars formed from a large cloud of gas making the stars roughly…

Red cloud of dust with a bright white star in the center of it. Lots of reddish and orangish stars in the background.

Caldwell 2

This shell of gas is expanding outward, away from the dying star within.

Large grouping of bright white, blue and red stars. Lightly colored blue dust surrounds the stars.

Caldwell 3

This barred spiral galaxy was first spotted by British astronomer William Herschel in April 1793 in the constellation Draco.