Astronomy

Two galaxies perform an intricate dance in this new Hubble Space Telescope image. The galaxies, containing a vast number of stars, swing past each other in a graceful performance choreographed by gravity.

The pair, known collectively as Arp 87, is one of hundreds of interacting and merging galaxies known in our nearby universe. Arp 87 was originally cataloged by astronomer Halton Arp in the mid 1960s. Arp’s Atlas of Peculiar Galaxies is a compilation of astronomical photographs using the 200-inch Hale and the 48-inch Samuel Oschin telescopes in Mount Palomar Observatory. The resolution in the Hubble image shows exquisite detail and fine structure that was not observable when Arp 87 was first cataloged in the 1960s.

The two main players comprising Arp 87 are NGC 3808 on the right (the larger of the two galaxies) and its companion NGC 3808A on the left. NGC 3808 is a nearly face-on spiral galaxy with a bright ring of star formation and several prominent dust arms. Stars, gas, and dust flow from NGC 3808, forming an enveloping arm around its companion. NGC 3808A is a spiral galaxy seen edge-on and is surrounded by a rotating ring that contains stars and interstellar gas clouds. The ring is situated perpendicular to the plane of the host galaxy disk and is called a “polar ring.”

Arp 87 is in the constellation Leo, the Lion, approximately 300 million light-years away from Earth. These observations were taken in February 2007 with the Wide Field Planetary Camera 2. Light from isolated blue, green, red, and infrared ranges was composited together to form this color image.

Image credits: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

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