Photographing the event horizon of the black hole in the center of the Milky Way is within reach in a few years * The diameter of the black hole that has consumed 4 million suns - barely reaches the orbit of Mercury
A new in-depth look into the core of the Milky Way galaxy is getting closer to the supermassive black hole than ever before. New methods promise to show the shadow of the mysterious object in the coming years.
In a recently published study, radio telescopes provided the first data on the diameter of the chaotic region of emissions surrounding the massive object.
The diameter of the black hole, which contains masses of 4 million masses, has so far been estimated at 23 million kilometers, which means that if we place it in the solar system it will not even reach the diameter of the orbit of Mercury around the sun. It cannot be seen because anything that approaches it, including light, is swallowed up within it. However, on the way to it, the material heats up to millions of degrees Celsius, and creates emissions in many wavelengths of the electromagnetic spectrum, from radio waves to X-rays.
In the last thirty years, astronomers have made progress in studying the causes of the radio emissions and identifying their distance from the black hole that creates them. The diameter of the radio wave region does not exceed 300 million kilometers, or roughly the orbit of the Earth. The researchers reported Thursday in the online edition of the journal Science.
The mystery remains
"We don't know the exact nature of the radio emission region, but as a result of these measurements we were able to narrow down the range of possible sizes," said Jeffrey Bower of the University of California, Berkeley. "We are getting much closer to seeing the black hole's effects on its environment than ever before." According to him, further observations may solve the mystery that still remains.
For now, the new observations bring us much closer to the black hole than before, Bewer added. The initial work was done using the National Science Foundation's Long Baseline Telescope Array.
blurred vision
The radio emission region called Sagittarius *A was discovered in 1974 and later was estimated to be related to the supermassive black hole at the center of the galaxy. The area is about 26 thousand light years from Earth.
The region is also obscured by dust clouds, so optical telescopes from Earth cannot study Sagittarius A*. Radio waves penetrate through the dust, but they are distorted by the hot gas swirling in the area. The astronomers said this blur prevented previous attempts to dig into the core of the activity. Bower likened it to trying to find a yellow rubber duck in a bubbling bathtub that is constantly being filled with streams of water that create steam from a shower.
To penetrate the cosmic fog, the crew looked for higher-frequency radio waves, coming from shorter wavelengths. They also used observations at longer wavelengths to estimate the effect of the perturbations, then removed those effects from the lower wavelength data.
After 30 years, the radio telescopes managed to penetrate through the haze and we see what's inside, said fellow researcher Heino Falcke of the Westerbork Radio Observatory in the Netherlands.
The researchers say the new observations rule out some less popular ideas about the origin of the radio emissions. But there's still room for improvement, Falk and Boer, using even shorter wavelengths to dig into the point of no return—the outer sphere of the black hole—and finally see the shadow of the giant dark object. Such observations are currently based solely on theories, which Falk and his colleagues proposed over four years ago.
"A picture of the black hole's event horizon is within our reach, if we work hard enough for the next few years," Falk said.
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