Deep Sky Object of the Month

Interacting galaxy pair NGC 4038-9. This pair is popularly known as the "Antennae" because of the long, curved filaments. POSS/DSS photo.

NGC 4038-9, often called the "Antennae" is an interacting pair of galaxies in western Corvus. At magnitude 10.3 and 10.6, these objects should be visible in even modest telescopes; larger instruments should show a wealth of detail.

In eight-inch and larger scopes, even a cursory glance shows that something is very different. Both galaxies are extended roughly east-west and touch at their east ends. Of the two galaxies, NGC 4038 is the brighter. Using a 12-inch scope at 200x, I noticed a generally knotty appearance, with two fairly prominent knots on the west edge of the main galaxy and another closer to the center. A spectacular sight!

Photographically, the most distinctive feature of this interacting pair is the long, sweeping filaments curving to the north and south. The filaments are probably stars and gas swept out by tidal forces as the two galaxies interact gravitationally. The knots seen in the photo above are large associations of young stars whose births were triggered by the interaction.

This system lies at a distance of 90 million light years. The main galaxy is about 100,000 light years across and has a mass of about 20 billion suns.

How to get there:

This pair of galaxies is located in western Corvus. Using Gamma Corvi as the starting point, they are about 3.5° west-southwest. Or, if you prefer to start from Eta Crater, the galaxies are 2.2° southeast.

Finder chart for NGC 4038-9