Arp 220 Appears to be a single, odd-looking
galaxy, but is in fact a nearby example of the aftermath of a
collision Between Two spiral galaxies. It is the brightest of
the three galactic mergers closest to Earth, about 250 million
light-years away in the constellation Serpens of, the Serpent.
The collision, Which Began about 700 million years ago, has
sparked a cracking burst of star formation, Resulting in about
200 huge star clusters in a packed, dusty region of about 5.000
light-years across (about 5 percent of the Milky Way's
diameter). The amount of gas in this tiny region equals the
amount of gas in the entire Milky Way Galaxy. The star clusters
are the bright bluish-white knots visible in the Hubble image.
Arp 220 glows brightest in infrared light and is an
ultra-luminous infrared galaxy. Previous Hubble Observations,
taken in the infrared at a wavelength that looks through the
dust, have uncovered the cores of the parent galaxies 1.200
light-years apart. Observations with NASA's Chandra X-ray
Observatory have also revealed X-rays coming from both cores,
Indicating the presence of two Supermassive Black Holes. Arp 220
is the 220th galaxy in Arp's Atlas of Peculiar Galaxies.