Spacecraft reveal new anatomy around a black hole
Scientists chose to study the black hole that lies at the heart of the Markarian 509 galaxy.
October 3, 2011
A fleet of spacecraft, including the European Space Agency’s (ESA) XMM-Newton and Integral, has shown unprecedented details close to a supermassive black hole. They reveal huge “bullets” of gas being driven away from the gravitational monster.
Active galaxy Markarian 509 as seen by the Hubble Space Telescope's WFPC2. Credit: NASA/ESA/J. Kriss (STScI)/J. de Plaa (SRON)
The black hole that the team chose to study lies at the heart of the galaxy Markarian 509, 500 million light-years away in space. This black hole is colossal, containing 300 million times the mass of the Sun and growing more massive every day as it continues to feed.
Markarian 509 was chosen because it is known to vary in brightness, which indicates that the flow of matter into the black hole is turbulent. The radiation from this inner region then drives an outflow of some gas away from the black hole.
The black hole was monitored for 100 days. "XMM-Newton really led these observations because it has such a wide X-ray coverage, as well as an optical monitoring camera," said Jelle Kaastra from the SRON Netherlands Institute for Space Research, who coordinated an international team of 26 astronomers from 21 institutes on 4 continents to make these observations.
During the campaign, the galaxy surpassed itself; instead of the usual 25 percent fluctuations in its brightness, it leapt up in the soft X-ray band by 60 percent, indicating that a major disturbance occurred in the gas flow to the black hole's deadly clutches.
The resulting observations have shown that the outflow consists of giant bullets propelled at millions of kilometers per hour. The bullets are stripped away from a dusty reservoir of matter waiting to fall into the black hole. The surprise is that the reservoir is situated more than 15 light years from the black hole. This is further than some astronomers thought was possible for the wind to originate.
"There has been a debate in astronomy for some time about the origin of the outflowing gas," said Kaastra.
The dusty gas reservoir takes the form of a doughnut-shaped torus that surrounds the black hole. Matter spirals in towards the black hole, creating an accretion disk in which the gas behaves like water spiraling down a plughole.
The observations also show that the accretion disk features a “skin” of gas with a temperature of millions of degrees. This is where the X-rays and gamma rays come from to drive the more distant gas outwards.
In addition to XMM-Newton and Integral, they used the NASA/ESA Hubble Space Telescope, NASA's Chandra and Swift satellites, and the ground-based telescopes WHT and PARITEL. Together the instruments gave them unprecedented wavelength coverage — running from the infrared, through the visible, ultraviolet, X-rays and into the gamma-ray band.
"The results underline how important long-term observations and monitoring campaigns are to gain a deeper understanding of variable astrophysical objects,” said Norbert Schartel from ESA. “XMM-Newton made all the necessary organizational changes to enable such observations, and now the effort is paying off."