How big can black holes grow

Black holes: a new way of measuring mass

In the centers of most galaxies there are black holes with millions to billions of solar masses. Astronomers can only draw conclusions about their properties from the behavior of matter in the vicinity of the supermassive objects. It is therefore extremely difficult to reliably determine the masses of these gravitational giants. An international team of researchers has now presented a new method in the journal “Nature” with which this task could be carried out surprisingly quickly in the future: All they do is measure the movement of certain gas molecules.

“With the next generation of telescopes, we can perform these observations at distances of over two hundred million light years,” reports Timothy Davis of the European Southern Observatory. “Then we won't even need five hours of observation time to determine the mass of these black holes.” For their current study, the researchers observed the galaxy NGC 4526 with a network of radio telescopes. In doing so, they focused on the emission of carbon monoxide molecules that were located near the central black hole.

Galaxy NGC 4526

In addition, the team simulated the behavior of such gas molecules in the computer, both in galaxies with and in those without a central black hole. Due to the enormous gravity of the black holes, the dynamics of the gas clouds change and show a different speed distribution than without such an influence, so the result. The scientists then compared their observation data with these theoretical models.

As a result, Davis and his colleagues estimate the mass of the black hole in NGC 4526 to be 450 million solar masses. It thus combines around a hundred times more mass than that in the center of the Milky Way. With the new method, the researchers hope to have found a convenient and reliable method that can be used to measure black holes in hundreds of galaxies.