in the constellation Fornax
2 million times the mass of the Sun
Eight times the diameter of the Sun
Although the supermassive black hole at the center of the galaxy NGC 1365 is relatively small, it has a big effect on the space around it. The black hole is spinning at close to the speed of light, dragging the surrounding space with it, creating a powerful spacetime vortex.
Astronomers have measured the spin with greater accuracy than for any other black hole yet discovered.
In July 2012, two space-based X-ray observatories observed the X-ray energy produced by iron atoms orbiting near the inner edge of the black hole's accretion disk, a wide, thin disk of hot gas that is spiraling into the black hole. The "fingerprint" of the iron atoms in the black hole's spectra is smeared.
Earlier observations had also detected the smearing, but they couldn't confirm the cause. It could have been the gravitational effect of the supermassive black hole, but it also could have been a blurring effect caused by intervening clouds of gas.
The 2012 observations were made by XMM-Newton, a European observatory, and NuStar, an American spacecraft. Their combined observations spanned a wide range of X-ray wavelengths, allowing astronomers to study the system in greater detail than ever before.
The observations eliminated the possibility of an intervening gas cloud and instead confirmed that the iron spectral lines were blurred by the black hole. By measuring how much the spectral lines were smeared, the astronomers then determined that NGC 1365's black hole is spinning at close to its theoretical limit.
The rapid spin rate reveals important details about the black hole's history. Supermassive black holes grow larger by ingesting gas, stars, and other material. If the material plowed into the black hole from random directions, the black hole would spin fairly slowly. The high rotation rate means the black hole grew from material funneling into it from one direction, or from the merger of two smaller black holes.
Such observations are important clues in the quest to understand the evolution of supermassive black holes and their surrounding galaxies, which are thought to have grown along with the black holes.
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This document was last modified: May 13, 2013.