NASA recently published an exquisite Hubble Space Telescope image of two interacting galaxies. The galaxies, containing a vast number of stars, appear to be performing a graceful dance under the influence of immense mutual gravitation.

The dazzling pair is known as Arp 87, as they were cataloged by astronomer Halton Arp in the 1960s. Arp compiled the Atlas of Peculiar Galaxies using the Palomar 200-inch Hale and the 48-inch Samuel Oschin telescopes. There are hundreds of interacting and colliding galaxies known in the nearby Universe.

The individual designations of the galaxies are NGC 3808 on the right (the larger of the two galaxies) and NGC 3808A on the left. NGC 3808 is a spiral galaxy, viewed nearly face-on. It shows a bright ring of star formation and several prominent dust arms.

Stars, gas, and dust stream from NGC 3808, forming an enveloping arm around its companion. NGC 3808A is an edge-on spiral galaxy, surrounded by a rotating ring of stars and interstellar gas clouds. The ring is oriented perpendicularly to the plane of the host galaxy disk and is termed a "polar ring".

Interacting galaxies typically have high rates of star formation. Some merging galaxies have the most energetic star formation processes in the nearby Universe.

Arp 87 is visible among the stars of the zodiacal constellation Leo, the Lion. The pair is approximately 300 million light-years distant. These observations were obtained in February 2007 with the Wide Field Planetary Camera 2. This color image represents blue, green, red, and infrared lights from the galaxies.

Further Reading

Hubble Site

http://hubblesite.org/

Aymen Mohamed Ibrahem

Senior Astronomy Specialist