Bonn astronomers discover how the image of a distant quasar splits into multiple images by the effects of a cloud of ionized gas in our own Milky Way Galaxy.
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. © Bill Saxton, NRAO/AUI/NSF
Grafische Darstellung eines Teils unserer Milchstraße von oben betrachtet. Unsere Sonne befindet sich in ungefähr 25000 Lichtjahren Entfernung vom Zentrum der Milchstraße (im Bild oben rechts). Die gestrichelte Linie zeigt die Richtung zum Quasar 2023+335, die durch die nahegelegene Cygnus-X-Region im lokalen Arm der Milchstraße führt. © R. Hurt, NASA/JPL-CalTech/SSC, nach Abb. 6 in Pushkarev et al.
Such events were predicted as early as in the 1970s, but the first evidence for one now has come from observations performed with the telescope array VLBA and analysed in the Max Planck Institute for Radio Astronomy.
The scientists observed the quasar 2023+335, nearly 3 billion light-years from Earth, as part of a long-term study of ongoing changes in some three hundred quasars. When they examined a series of images of 2023+335, they noted dramatic differences. The differences, they said, are caused by the radio waves from the quasar being bent as they pass through the Milky Way gas cloud, which moved through our line of sight to the quasar. "So as we would see a spot of light get broader or even multiple behind a frosted glass, we see this quasar 'dancing' behind a gas cloud in our own Galaxy", so Anton Zensus, Director at the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, and member of the international team who has discovered this effect. "This is similar to the fata morgana to be seen in the desert or to the Sun dogs caused by iced clouds with the image of our own star", adds Zensus.
"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," said Alexander Pushkarev from the MPIfR in Bonn, Germany, and the Crimean Astrophysical Observatory, Ukraine, and leader of the international team.
New insights into turbulent galactic gas clouds become tangible
The scientists added 2023+335 to their list of observing targets in 2008. Their targets, in the framework of the MOJAVE project, are quasars and other galaxies with supermassive black holes at their cores. The gravitational energy of the black holes powers "jets" of material propelled to nearly the speed of light. The quasar 2023+335 initially showed a typical structure for such an object, with a bright core and a jet. In 2009, however, the object's appearance changed significantly, showing what looked like a line of bright, new radio-emitting spots.
"We've never seen this type of behaviour before, either among the hundreds of quasars in our own observing program or among those observed in other studies," adds Eduardo Ros from the MPIfR, also a team member in the discovery.
Gas clouds could also refract the light of other quasars
The multiple-imaging event came as other telescopes detected variations in the radio brightness of the quasar, caused, the astronomers said, by scattering of the waves.
The scientists' analysis indicates that the quasar's radio waves were bent by a turbulent cloud of charged gas nearly 5,000 light-years from Earth in the direction of the constellation Cygnus. The cloud's size is roughly comparable to the distance between the Sun and Mercury, and the cloud is moving through space at about 56 kilometres per second (or 200.000 km/h, comparable to the speed of Helios 2, the fastest spacecraft constructed ever).
"Monitoring of 2023+335 over time may yield more such events, so we can learn additional details both about the process by which the waves are scattered and about the gas that does the scattering. Other quasars that are seen through similar regions of the Milky Way also may show this behaviour", concludes Pushkarev.
The monitoring program that yielded this discovery is called MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments), run by an international team of scientists led by Matt Lister from Purdue University. The researchers recently published their results in the journal Astronomy and Astrophysics.
ContactDr. Alexander Pushkarev
Astronomy & Astrophysics, July 2013
Dr. Alexander Pushkarev | Max-Planck-Institute
A tale of two pulsars' tails: Plumes offer geometry lessons to astronomers
18.01.2017 | Penn State
Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Power and Electrical Engineering
18.01.2017 | Materials Sciences
18.01.2017 | Life Sciences