Black Holes

What does this image show? It looks very different from images that typically appear on our web-site, of galaxies and star clusters and exploded stars. It looks vaguely like a swarm of moths but with rectangular shapes that don't really look like wings. It might also pass for abstract art.

The answer is an astronomical one: this is a large mosaic showing Chandra observations from its archive centered on the Virgo Cluster. The rectangles are sets of charge-coupled devices (CCDs) on Chandra, showing X-ray emission from hot gas in the cluster's atmosphere, or around black holes. The rectangles often come in pairs because this is how a common configuration of Chandra CCDs appears on the sky: two square CCDs next to a set of three. The observations are scattered around because they targeted many different galaxies in and around Virgo.

New results based on the two objects shown here are challenging the prevailing ideas as to how supermassive black holes grow in the centers of galaxies. NGC 4342 and NGC 4291, the two galaxies in the study, are nearby in cosmic terms at distances of 75 million and 85 million light years respectively. In these composite images, X-rays from NASA's Chandra X-ray Observatory are colored blue, while infrared data from the 2MASS project are seen in red.

Astronomers had known from previous observations that these galaxies host black holes with unusually large masses compared to the mass contained in the central bulge of stars. To study the dark matter envelopes contained in each galaxy, Chandra was used to examine their hot gas content, which was found to be widespread in both objects.

This computer-simulated image shows gas from a star that is ripped apart by tidal forces as it falls into a black hole. Some of the gas also is being ejected at high speeds into space.

Today we have a guest blogger, Uroš Kostić, who is currently a researcher at the Faculty of Mathematics and Physics at the University of Ljubljana in Slovenia. Here, he describes theoretical work on the destruction of asteroids by supermassive black holes, involving a collaboration between University of Ljubljana, Slovenia, and Astronomical Observatory in Padova, Italy, from 2005 - 2008. During the project, Uroš was preparing his PhD at University of Ljubljana under the supervision of Professor Andrej Čadež.

These results by Uroš were referenced by Kastytis Zubovas in the paper that we publicized last month (http://chandra.si.edu/photo/2012/sgra/). We were unable to mention the work by Uroš and his team in the release, but we felt that the originality of their work, published before the Zubovas et al. study, warranted a blog posting. Academic research invariably builds on the work done by others and to paraphrase Isaac Newton: "If I have seen further it is by standing on the shoulders of giants."

This artist's impression shows a binary system containing a stellar-mass black hole called IGR J17091-3624, or IGR J17091 for short. The strong gravity of the black hole, on the left, is pulling gas away from a companion star on the right. This gas forms a disk of hot gas around the black hole, and the wind is driven off this disk.

This image from NASA's Chandra X-ray Observatory shows the center of our Galaxy, with a supermassive black hole known as Sagittarius A* (Sgr A* for short) in the center. Using intermittent observations over several years, Chandra has detected X-ray flares about once a day from Sgr A*. The flares have also been seen in infrared data from ESO's Very Large Telescope in Chile.

On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist's illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star. The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets.

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). Using the Chandra image, the flow of hot gas toward the supermassive black hole in the center of this galaxy has been imaged. This is the first time that clear evidence for such a flow has been observed in any black hole.

The center of this image contains an extraordinary gamma-ray burst (GRB) called GRB 110328A, observed with NASA's Chandra X-ray Observatory. This Chandra observation confirms the association of GRB 110328A with the core of a distant galaxy and shows that it was an exceptionally long lived and luminous event compared to other GRBs.

This optical and infrared image from the Digitized Sky Survey shows the crowded field around the binary system GRS 1915+105 (GRS 1915 for short) located near the plane of our Galaxy. The top-left inset shows a close-up of the Chandra image of GRS 1915 , and the bottom-right inset shows the remarkable "heartbeats" seen in the X-ray light from this system. Using Chandra and the Rossi X-ray Timing Explorer (RXTE), astronomers have discovered what drives these heartbeats and given new insight into the ways that black holes can regulate their intake and severely curtail their growth.