New evidence of galactic black hole.Astronomers have repeatedly reported evidence that black holes lurk at the centers of galaxies. However, the latest finding all but settles the case, many scientists assert. Using a continent-wide array of radio telescopes, a U.S.-Japanese team last week reported "compelling evidence" that the center of a relatively nearby galaxy harbors a black hole as massive as 40 million suns.
The unusually high resolution of the network of 10 radio telescopes, collectively known as the Very Long Baseline Array The Very Long Baseline Array (VLBA) is a system of ten radio telescopes controlled remotely from the Array Operations Center in Socorro, New Mexico (USA) by the National Radio Astronomy Observatory. (VLBA VLBA Very Long Baseline Array (radio telescope)
VLBA Victorian Ladies' Bowling Association (Australia)
VLBA Vans Leave Barn At
VLBA Very Large Business Application
VLBA Virginia Licensed Beverage Association ), enabled researchers to record structures deep within the spiral galaxy NGC NGC New General Catalogue (of Nebulae and Star Clusters; astronomy)
NGC National Geographic Channel (TV)
NGC National Guideline Clearinghouse 4258, which lies some 21 million light-years from Earth.
Spotting details 1,000 times smaller than those detected by visible-light telescopes, the team measured with unprecedented accuracy the swirling motion of a disk of gas and dust orbiting the galactic core. The inner part of the disk lies only about one-third of a light-year from the galaxy's center.
From this motion, clocked at 900 kilometers per second, the team infers that the core has a minimum density of 100 million suns per cubic light-year. That number exceeds the density of any other galactic center ever measured.
A cluster of ordinary stars with that density would have been torn apart long ago by collisions between individual stars, notes James M. Moran
James Martin "Jim" Moran (August 8 1918 – April 24 2007) was an American car dealer and philanthropist whose net worth of $2. of the Harvard-Smithsonian Center for Astrophysics The Harvard-Smithsonian Center for Astrophysics (CfA) is located in Cambridge, Massachusetts. It consists of the Harvard College Observatory and the Smithsonian Astrophysical Observatory. The Center is located at 60 Garden Street. in Cambridge, Mass. His team says it has no choice but to conclude that the heart of NGC 4258 contains a supermassive black hole.
Moran and his colleagues reported their findings last week at a meeting of the American Astronomical Society The American Astronomical Society (AAS, sometimes pronounced "double-A-S") is a US society of professional astronomers and other interested individuals, headquartered in Washington, DC. in Tucson. They provide further details in the Jan. 12 Nature and the upcoming Feb. 20 Astrophysical Journal.
"The work...provides what may constitute the strongest case yet for a supermassive black hole in a galactic nucleus," writes Richard Barvainis of the Massachusetts Institute of Technology's Haystack Observatory in Westford. His commentary accompanies the Nature report.
"I was really blown away by their use of the [radio telescope] technology," says Patrick S. Osmer of Ohio State University Ohio State University, main campus at Columbus; land-grant and state supported; coeducational; chartered 1870, opened 1873 as Ohio Agricultural and Mechanical College, renamed 1878. There are also campuses at Lima, Mansfield, Marion, and Newark. in Columbus. "Maybe the public thinks that black holes have already been proved to exist, but this current study is much more definite. [The researchers] have probed much closer to the center of the galaxy than before."
If they indeed exist, black holes by their very nature can't be seen; astronomers must deduce their presence from their gravitational grav·i·ta·tion
a. The natural phenomenon of attraction between physical objects with mass or energy.
b. The act or process of moving under the influence of this attraction.
2. tug on surrounding stars, dust, or gas. Last year, another team made headlines when it used the Hubble Space Telescope Hubble Space Telescope (HST), the first large optical orbiting observatory. Built from 1978 to 1990 at a cost of $1.5 billion, the HST (named for astronomer E. P. Hubble) was expected to provide the clearest view yet obtained of the universe. to infer the existence of a massive black hole at the core of the elliptical galaxy M87 (SN: 6/4/94, p.356).
In the new study, Moran and his colleagues used the VLBA to study radio emissions produced by water molecules within a central galactic disk. The molecules act as masers, amplifying microwave radio emissions in much the same way a laser amplifies visible light and produces intense, pencil-thin beams of radiation. Because of the edge-on orientation of the disk, some of these beams shoot toward Earth, providing a clear view of the dynamics at the center of the galaxy. Unlike visible light, radio waves Radio waves
Electromagnetic energy of the frequency range corresponding to that used in radio communications, usually 10,000 cycles per second to 300 billion cycles per second. easily penetrate the dust present at the core of many galaxies.
"The work is enormously compelling," says Martin J. Rees of the University of Cambridge in England. "It's much better than all the public hype from the Hubble Space Telescope and M87."