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Arp 220 (Interacting Galaxy)


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Arp 220
Interacting Galaxy (相互作用銀河)

Gx Sd

別名 (Other names)
IC 1127, IC 4553, PGC 55497, UGC 09913, VV 540, KPG 470

明るさ (Brightness)
13.4等級

星座 (Constellation)
へび座 (Ser) (Serpens)

距離 (Distance)
2億5,000万光年 (250 million light-years)

Arp 220 is an interacting galaxy located 250 million light years from the Earth in the constellation Serpens.

Arp 220 (Interacting Galaxy) : Picture

Arp220 Arp220
Arp 220
(C) NASA
Arp 220
(C) NASA
Arp220 Arp220
Arp 220
(C) NASA
Arp 220
(C) NASA

Interacting Galaxy Arp 220
Interacting Galaxy Arp 220
(C) NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
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 of Serpens, 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 about 5,000 light-years across. The amount of gas in this tiny region equals the amount of gas in the entire Milky Way Galaxy. The star clusters are the bluish-white bright 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.

Arp 220: Spirals in Collision
Arp 220: Spirals in Collision
(C) R. Thompson (U. Arizona) et al., NICMOS, HST, NASA
Arp 220 is the brightest object in the local universe. But why does it shine so brightly? Arp 220 was cataloged as a peculiar galaxy in the 1960s. In the late 1980s, it was discovered to be an ultraluminous infrared galaxy and headed a list compiled from observations with the now-defunct IRAS satellite. New observations with the Hubble Space Telescope are quite revealing. Photos by NICMOS in the infrared taken in April and released just last week now better resolve the two colliding spiral galaxies at the center of Arp 220. A result of this spiral collision are fantastic knots of new star formation visible as the bright spots on the above photograph. Below the "half-moon" shaped knot on the right is a massive disk of dust possibly hiding a dying spiral's central black hole. The bright knot to the left is the center of the other broken spiral galaxy. The galaxy cores are about 1,200 light years apart and are orbiting each other.

Active Black Hole Squashes Star Formation
Active Black Hole Squashes Star Formation
(C) NASA/JPL-Caltech
New data from the Herschel Space Observatory shows that galaxies with the most powerful, active, supermassive black holes at their cores produce fewer stars than galaxies with less ones.

Supermassive black holes are believed to reside in the hearts of all large galaxies. When gas falls upon these monsters, the materials are accelerated and heated around the black hole, releasing great torrents of energy. In the process, active black holes often generate colossal jets that blast out twin streams of heated matter.

Inflows of gas into a galaxy also fuel the formation of new stars. In a new study of distant galaxies, Herschel helped show that star formation and black hole activity increase together, but only up to a point. Astronomers think that if an active black hole flares up too much, it starts spewing radiation that prevents raw material from coalescing into new stars.

This artist concept of the local galaxy Arp 220, captured by the Hubble Space Telescope, helps illustrate the Herschel results. The bright core of the galaxy, paired with an overlaid artist's impression of jets emanating from it, indicate that the central black hole's activity is intensifying. As the active black hole continues to rev up, the rate of star formation will, in turn, be suppressed in the galaxy. Astronomers want to further study how star formation and black hole activity are intertwined.
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