Arp 220

Arp 220 is a remarkable system located deep in space. It is the result of a massive collision between two galaxies. These two galaxies are currently in the process of merging into one. This object holds the 220th spot in the Atlas of Peculiar Galaxies. That atlas was created by the astronomer Halton Arp. Arp 220 is a very important subject for scientists to study. It is considered a prototypical ultraluminous infrared galaxy, or ULIRG. This means it is a galaxy that shines with an incredible amount of infrared light.

The way Arp 220 works is driven by the physics of the collision. When the two galaxies began to merge, it triggered a starburst. A starburst is a massive, sudden burst of new star formation. This process releases a huge amount of energy. Most of this energy output is found in the far-infrared part of the light spectrum. This means the galaxy glows brightly in light that our eyes cannot see. This energy is likely caused by the intense activity of creating new stars. The merging process acts as a trigger for this cosmic event.

Astronomers have identified several distinct features within this merging system. One major feature is the presence of massive star clusters. Observations from the Hubble Space Telescope revealed more than 200 of these huge clusters. These clusters are located in the central part of the galaxy. Some of these clusters are incredibly large and heavy. The most massive cluster contains enough material to equal about 10 million suns. Another feature is the presence of masers. Arp 220 contains at least two bright maser sources. These include an OH megamaser and a water maser.

Our understanding of Arp 220 has grown through many historical discoveries. In 1984, the IRAS mission discovered its massive energy output. It showed that the galaxy was dominated by far-infrared light. Later, the Hubble Space Telescope took important images in 1997 and 2002. It used instruments called the ACS and NICMOS to see visible and infrared light. In October 2011, astronomers spotted a record-breaking event in the galaxy. They found seven supernovas all occurring at the same time. A supernova is the powerful explosion of a star. This was a very rare and significant discovery for science.

The scale of Arp 220 is truly immense. It is located 250 million light years away from Earth. This distance makes it the closest ultraluminous infrared galaxy to our home. The merger of the two galaxies actually started about 700 million years ago. This is a very long period of time for a collision to continue. Astronomers also found organic molecules in the galaxy using the Arecibo Observatory. These molecules are the building blocks of complex chemistry. Such details help scientists understand the environment within the merging stars.

There are many surprising facts about the core of this galaxy. X-ray observations have been made by the Chandra and XMM-Newton satellites. These satellites suggest that Arp 220 likely includes an active galactic nucleus, or AGN. An AGN is a very bright and active center at a galaxy's core. This discovery raises important questions for researchers. They want to know if galaxy mergers are what create these active centers. It is believed that mergers might also give rise to supermassive black holes. These black holes are thought to power the energy of an AGN.

Arp 220 connects to many broader ideas in the study of the universe. It serves as a local example of objects found in large numbers by sky surveys. These surveys use instruments like the SCUBA at the James Clerk Maxwell Telescope. These tools look at submillimetre wavelengths to find luminous objects. By studying Arp 220, scientists can learn about distant, similar galaxies. It helps us understand the link between galactic mergers and the birth of stars. It also helps us understand how the most powerful centers of galaxies form. This system is a vital piece of the cosmic puzzle.