Article Posted on : - Jul 30, 2011

The galaxy NGC 3115 is shown here in a composite image of data from NASA's Chandra X-ray Observatory and the European Southern Observatory's Very Large Telescope (VLT). Photo by NASA/CXC/Univ. of Alabama/K. Wong et al; Optical: ESO/VLT.

WASHINGTON (BNS): The flow of hot gas toward a black hole has been imaged for the first time in X-rays.

The observations from NASA's Chandra X-ray Observatory will help understand how black holes grow and how matter behaves in their intense gravity, NASA said.

The black hole is at the centre of a large galaxy known as NGC 3115, which is located about 32 million light years from Earth.

By imaging the hot gas at different distances from this supermassive black hole, astronomers have observed a critical threshold where the motion of gas first becomes dominated by the black hole's gravity and falls inward. This distance from the black hole is known as the "Bondi radius."

As gas flows toward a black hole, it becomes squeezed, making it hotter and brighter, a signature now confirmed by the X-ray observations.

The researchers found the rise in gas temperature begins about 700 light years from the black hole, giving the location of the Bondi radius.

This suggests the black hole in the center of NGC 3115 has a mass about two billion times that of the sun, making it the closest black hole of that size to Earth, they said.

The Chandra data also show the gas close to the black hole in the center of the galaxy is denser than gas further out.

Using the observed properties of the gas and theoretical assumptions, the team then estimated that each year gas weighing about 2 percent the mass of the sun is being pulled across the Bondi radius toward the black hole.