Sagittarius A*

Sagittarius A * (pronounced Sagittarius A star; abbreviated Sgr A *, a region in the constellation Sagittarius ) is a source of radio waves in the center of the Milky Way. According to the current state of radio astronomy research, it involves a supermassive black hole of about 4 million solar masses, which is located at the point that represents the center of the Milky Way.

The discovery of the super -massive black hole managed independent teams to Andrea Ghez at the Keck Observatory and Reinhard Genzel at La Silla Observatory and the Very Large Telescope in multi-year series of observations from the 1990s.

Objects in the environment of Sgr A *

Stars

2002, scientists (by Reinhard Genzel ), the research on Very Large Telescope of the European Southern Observatory ( ESO), observe a star, the Sagittarius A * region at 17 hours of light (~ 18.36 billion kilometers ) had approached. The researchers were able to recognize their observations a sudden U-turn of the 15 solar masses heavy star S0 -2 (or " S2" ). Due to the high velocity of the star, this process can only be interpreted as orbital motion around a black hole. Due to the small distance of S0 2 to the enormous mass of the black hole 's rotational speed is very high; its web speed of up to 5000 km / s Its orbit is relatively stable; only if S0 -2 has approached the black hole 16 light minutes, it will be torn apart by tidal forces. For one revolution around the center of S0 -2 requires only 15.2 years. For another star, the 16- times fainter star S0 -102, 2012, the orbit was also measured and an even shorter period of 11.5 years measured. Both of these stars are so far the only objects that have been observed in such a short distance from Sgr A *.

The observation of the star S0 -2 in its movement around Sagittarius A * was made possible by an adaptive optics system ( NAOS ) can compensate for the disturbing influences of the atmosphere. Through this observation method, it is now possible to exclude that it is Sgr A * to something else acts as a supermassive black hole - for example, a bunch of neutron stars.

Gas cloud

Researchers at the Max Planck Institute for Extraterrestrial Physics, also discovered a gas cloud with about three times the mass of the Earth, is moving towards Sagittarius A * and in 2013 only 40 billion kilometers (37 hours of light ) will be removed from the black hole. Already, the cloud is pulled apart and brought up by the ultraviolet radiation of nearby stars to shine. Through further observations over the next few years, the researchers hope to information about the physical processes during the approach to a black hole.

Second Black Hole

In 2004 was discovered with the Gemini Telescope in Hawaii with IRS 13, a second black hole, which has a mass of about 1300 solar masses and Sagittarius A * accompanied at intervals of three light years. For IRS 13 is considered accurate to a group of seven stars that revolve around a common center of gravity. Studies point out there on a medium-sized black hole. This surrounds Sgr A * in a confined space with an unusually high speed of about 280 km / s Another indication of the existence of a black hole is next to the high speeds, the X-ray radiation, which is emitted from IRS 13.

More Black Holes

In January 2005, were observed with the X-ray telescope Chandra outbursts near Sgr A *, which suggest that there are 10,000 to 20,000 black holes within about 70 light years, the supermassive central black hole in Sgr A * orbit. Thus, a circulating since 2003 theory is supported by the "fed" the central black hole through smaller holes: The small black holes accumulate in the areas outside located on the Milky Way bulge of stars around them, which they then hold captive until they have moved on a spiral path to the immediate vicinity of Sgr a *. There the star clusters are eventually resolved by the extremely large tidal forces and lose one or the other star of the super -massive black hole. The previous theory to the feeding process was assumed that a huge ring-shaped cloud of gas orbiting the black hole and it is becoming increasingly difficult. Once a critical mass is exceeded, the cloud collapses and falls into the center of the Milky Way. Probably both processes play an important role in the feeding of Sgr A *.