NASA RXTE: Clouds seen circling supermassive black holes - video

Credit: NASA

Astronomers see huge clouds of gas orbiting supermassive black holes at the centers of galaxies using NASA's Rossi X-Ray Timing Explorer satellite (RXTE).

Once thought to be a relatively uniform, fog-like ring, the accreting matter instead forms clumps dense enough to intermittently dim the intense radiation blazing forth as these enormous objects condense and consume matter, they report in a paper to be published in the Monthly Notices of the Royal Astronomical Society, available online now.

Evidence for the clouds comes from records collected over 16 years by NASA's Rossi X-Ray Timing Explorer satellite (RXTE), a satellite in low-earth orbit equipped with instruments that measured variations in X-ray sources.

Those sources include active galactic nuclei, brilliantly luminous objects powered by supermassive black holes as they gather and condense huge quantities of dust and gas.

By sifting through records for 55 active galactic nuclei Alex Markowitz, an astrophysicist at the University of California, San Diego and the Karl Remeis Observatory in Bamberg, Germany and colleagues found a dozen instances when the X-ray signal dimmed for periods of time ranging from hours to years, presumably when a cloud of dense gas passed between the source and satellite.

Mirko Krumpe

Mirko Krumpe of the European Southern Observatory in Garching, Germany and Robert Nikutta, of Andrés Bello University in Santiago, Chile co-authored the report, which confirms what recent models of these systems have predicted.


This animation shows an artist's rendition of the cloudy structure revealed by a study of data from NASA's Rossi X-Ray Timing Explorer satellite (RXTE). Credit: NASA

The clouds they observed orbit a few light-weeks to a few light-years from the center of the active galactic nuclei.

One, in a spiral galaxy in the direction of the constellation Centaurus designated NGC 3783, appeared to be in the midst of being torn apart by tidal forces.

More Information: 'First X-ray-Based Statistical Tests for Clumpy-Torus Models: Eclipse Events from 230 Years of Monitoring of Seyfert AGN': Alex Markowitz (Univ. Calif., San Diego and Karl Remeis Sternwarte/ECAP), Mirko Krumpe (European Southern Observatory and Univ. Calif., San Diego), Robert Nikutta (Univ. Andrés Bello): arXiv:1402.2779 [astro-ph.GA]

NASA: MODIS snap Cyclone Oli circling over Tahiti

Cyclone Oli was a Category 4 storm on February 4, 2010, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this true-color image.

The powerful storm was moving southeast across the South Pacific over the French Polynesian Islands.

Tahiti, the most populous of the islands, is under the outer edge of the storm in the upper right.

According to the Joint Typhoon Warning Center, Oli had winds of 213 kilometers per hour (132 miles per hour or 115 knots) at 1:40 p.m., local time, when this image was acquired. Forecasters expected the storm to weaken as it continued to move south over cooler waters.

At least 3,400 people were evacuated from Tahiti and nearby islands as Oli approached, reported BBC News. The storm’s strong winds damaged homes and power lines. One person died and several others were injured in the storm, said BBC News.

The highest resolution version of the image is provided above. The image is available in additional resolutions from the MODIS Rapid Response System.