August 29, 2013
Astronomers Observe Quasar Split Into Multiple Images Due To Milky Way Gas Cloud
redOrbit Staff & Wire Reports - Your Universe Online
Using the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope system, astronomers have for the first time managed to capture an image of a distant quasar split into multiple images due to the effects of a cloud of ionized gas in the Milky Way.
While these events were first predicted some four decades ago, the VLBA has managed to obtain the first evidence of their existence. Using the array, the researchers observed the quasar 2023+335, which is located approximately three billion light-years from Earth, as part of a long-term study of ongoing changes in roughly 300 quasars.
Purdue University astrophysicist Matt Lister and his colleagues examined a series of images of this particular quasar and noticed “dramatic” differences. Those differences, they explained, are caused by radio waves from the quasar being bent as they pass through the gas cloud, which moved into their line-of-sight to the quasar.
Quasar 2023+335 was added to the scientists’ list of observing targets, which include quasars and other galaxies with supermassive black holes at their cores, five years ago. This particular quasar initially showed a structure typical for this kind of object, with a bright core and a jet.
However, in 2009, 2023+335’s appearance changed significantly, showing what appeared to be a line of bright, new radio-emitting spots. The multiple-imaging event came when other telescopes detected variations in the quasar’s radio brightness, which the astronomers believe was caused by the scattering of the waves.
“This event, obviously rare, gives us a new way to learn some of the properties of the turbulent gas that makes up a significant part of our Galaxy,” Lister said. “We've never seen this type of behavior before, either among the hundreds of quasars in our own observing program or among those observed in other studies.”
Lister and his colleagues report their analysis indicates that a charged gas cloud located almost 5,000 light years from Earth in the direction of the constellation Cygnus bent the quasar’s radio waves. That cloud, which they describe as turbulent, is about as large as the distance between Mercury and the Sun, and the cloud itself is travelling through space at a reported speed of nearly 35 miles (56 kilometers) per second.
Continued observation of 2023+335 could lead to the discovery of additional events like this, the study authors said. If that were to occur, it could help Lister’s team uncover additional information about the process by which the waves that are scatters, as well as the gas cloud actually responsible for causing the phenomenon. Furthermore, they might be able to witness this behavior in other quasars viewed through similar regions of the Milky Way.
The researchers recently published their results in the journal Astronomy and Astrophysics.
Image 2 (below): Artist's Diagram of the refraction event (not drawn to scale), showing how radio waves from the distant quasar jet are bent by a gas cloud in our own Galaxy, creating multiple images seen with the Very Long Baseline Array. Credit: Bill Saxton, NRAO/AUI/NSF