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More about black holes

Astronomers observe how the black hole of the Milky Way crushed material around

Tuesday 11/18/2008 20:31 (CET ) ELMUNDO.ES
MADRID .- An international team involving the Consejo Superior de Investigaciones Científicas (CSIC) has observed what happens in the environment of Sagittarius A * (Sgr A *), the supermassive black hole with a mass of four million higher than the sun, still eating matter at the center of the galaxy.

Researchers with the VLT and APEX telescopes located in Chile, have detected intense flares, a product of the clouds of tear gas that spin at high speed around the hole before falling on it. Black holes are difficult to observe, but SgrA * is a particularly challenging goal because in the center of the Milky Way there are huge amounts of gas and dust that cause the radiation emitted by objects in the visible wavelength, the type light we see with our eyes on the road are extinguished. Therefore, the study of this region must be performed at frequencies of the electromagnetic spectrum capable of penetrating this veil: the more the better, since it is the only way to get a complete picture of the phenomenon. Thus the researchers have used the VLT and APEX telescopes that capture infrared and submillimeter waves respectively. This is the first time you get simultaneous measurements of lightning with these instruments.

SgrA * is visible only in infrared light for short periods of time, when shows strong flares. And as you can not predict when these events occur is not easy to observe with two telescopes that are not in the same place, because a single cloud could cover the region Sky interest. In addition, "we must be very patient," explains Rainer Schödel, Institute of Astrophysics of Andalucia (CSIC Granada). After several nights of waiting, responsible for the VLT astronomers discovered that SgrA * was activated, and its brightness increased every minute. Alerted their colleagues in the APEX and during the next six hours, found violent variations in the brightness of Sgr A *, plus four major flares.

As expected astronomers first recorded flares at infrared wavelengths, and an hour and a half later, submillimeter wave. This is due to the expansion of the gas clouds that eventually fall the hole: the speed with which revolve in the last orbits around Sgr A * is stretched, increasing its size and becoming more transparent. "At the moment we can only perceive the issue of SgrA * as a point of light. However, as in astronomical terms is close to the Earth, which is relatively large, in five or ten years, we hope to be able to directly observe the gas swirling around them, "concludes Schödel.