This accomplishment opens new avenues for research, including a novel way to probe emission regions near supermassive black holes. It may even be possible to find other gravitational lenses with data from the Fermi Gamma-ray Space Telescope.
This Hubble image of gravitational lens B0218+357 reveals two bright sources separated by about a third of an arcsecond, each an image of the background blazar. Spiral arms belonging to the lensing galaxy also can be seen. B0218+357 boasts the smallest separation of lensed images currently known. Image Credit: NASA/ESA and the Hubble Legacy Archive
"We began thinking about the possibility of making this observation a couple of years after Fermi launched, and all of the pieces finally came together in late 2012," said Teddy Cheung, lead scientist for the finding and an astrophysicist at the Naval Research Laboratory in Washington.
In September 2012, Fermi's Large Area Telescope (LAT) detected a series of bright gamma-ray flares from a source known as B0218+357, located 4.35 billion light-years from Earth in the direction of a constellation called Triangulum. These powerful flares, in a known gravitational lens system, provided the key to making the lens measurement.
Astronomers classify B0218+357 as a blazar -- a type of active galaxy noted for its intense emissions and unpredictable behavior. At the blazar's heart is a supersized black hole with a mass millions to billions of times that of the sun. As matter spirals toward the black hole, some of it blasts outward as jets of particles traveling near the speed of light in opposite directions.
The extreme brightness and variability of blazars result from a chance orientation that brings one jet almost directly in line with Earth. Astronomers effectively look down the barrel of the jet, which greatly enhances its apparent emission.
Long before light from B0218+357 reaches us, it passes directly through a face-on spiral galaxy -- one very much like our own -- about 4 billion light-years away.
The galaxy's gravity bends the light into different paths, so astronomers see the background blazar as dual images. With just a third of an arcsecond (less than 0.0001 degree) between them, the B0218+357 images hold the record for the smallest separation of any lensed system known.
While radio and optical telescopes can resolve and monitor the individual blazar images, Fermi's LAT cannot. Instead, the Fermi team exploited a "delayed playback" effect.
"One light path is slightly longer than the other, so when we detect flares in one image we can try to catch them days later when they replay in the other image," said team member Jeff Scargle, an astrophysicist at NASA's Ames Research Center in Moffett Field, Calif.
In September 2012, when the blazar's flaring activity made it the brightest gamma-ray source outside of our own galaxy, Cheung realized it was a golden opportunity. He was granted a week of LAT target-of-opportunity observing time, from Sept. 24 to Oct. 1, to hunt for delayed flares.
At the American Astronomical Society meeting in National Harbor, Md., Cheung said the team had identified three episodes of flares showing playback delays of 11.46 days, with the strongest evidence found in a sequence of flares captured during the week-long LAT observations.
Intriguingly, the gamma-ray delay is about a day longer than radio observations report for this system. And while the flares and their playback show similar gamma-ray brightness, in radio wavelengths one blazar image is about four times brighter than the other.
Astronomers don't think the gamma rays arise from the same regions as the radio waves, so these emissions likely take slightly different paths, with correspondingly different delays and amplifications, as they travel through the lens.
"Over the course of a day, one of these flares can brighten the blazar by 10 times in gamma rays but only 10 percent in visible light and radio, which tells us that the region emitting gamma rays is very small compared to those emitting at lower energies," said team member Stefan Larsson, an astrophysicist at Stockholm University in Sweden.
As a result, the gravity of small concentrations of matter in the lensing galaxy may deflect and amplify gamma rays more significantly than lower-energy light. Disentangling these so-called microlensing effects poses a challenge to taking further advantage of high-energy lens observations.
The scientists say that comparing radio and gamma-ray observations of additional lens systems could help provide new insights into the workings of powerful black-hole jets and establish new constraints on important cosmological quantities like the Hubble constant, which describes the universe's rate of expansion.
The most exciting result, the team said, would be the LAT's detection of a playback delay in a flaring gamma-ray source not yet identified as a gravitational lens in other wavelengths.
A paper describing the research will appear in a future edition of The Astrophysical Journal Letters.
NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership. Fermi is managed by NASA's Goddard Space Flight Center in Greenbelt, Md. It was developed in collaboration with the U.S. Department of Energy, with contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.J. D. Harrington
Francis Reddy | EurekAlert!
Present-day measurements yield insights into clouds of the past
27.05.2016 | Paul Scherrer Institut (PSI)
NASA scientist suggests possible link between primordial black holes and dark matter
25.05.2016 | NASA/Goddard Space Flight Center
A biological and energy-efficient process, developed and patented by the University of Innsbruck, converts nitrogen compounds in wastewater treatment facilities into harmless atmospheric nitrogen gas. This innovative technology is now being refined and marketed jointly with the United States’ DC Water and Sewer Authority (DC Water). The largest DEMON®-system in a wastewater treatment plant is currently being built in Washington, DC.
The DEMON®-system was developed and patented by the University of Innsbruck 11 years ago. Today this successful technology has been implemented in about 70...
Permanent magnets are very important for technologies of the future like electromobility and renewable energy, and rare earth elements (REE) are necessary for their manufacture. The Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany, has now succeeded in identifying promising approaches and materials for new permanent magnets through use of an in-house simulation process based on high-throughput screening (HTS). The team was able to improve magnetic properties this way and at the same time replaced REE with elements that are less expensive and readily available. The results were published in the online technical journal “Scientific Reports”.
The starting point for IWM researchers Wolfgang Körner, Georg Krugel, and Christian Elsässer was a neodymium-iron-nitrogen compound based on a type of...
In the Beyond EUV project, the Fraunhofer Institutes for Laser Technology ILT in Aachen and for Applied Optics and Precision Engineering IOF in Jena are developing key technologies for the manufacture of a new generation of microchips using EUV radiation at a wavelength of 6.7 nm. The resulting structures are barely thicker than single atoms, and they make it possible to produce extremely integrated circuits for such items as wearables or mind-controlled prosthetic limbs.
In 1965 Gordon Moore formulated the law that came to be named after him, which states that the complexity of integrated circuits doubles every one to two...
Characterization of high-quality material reveals important details relevant to next generation nanoelectronic devices
Quantum mechanics is the field of physics governing the behavior of things on atomic scales, where things work very differently from our everyday world.
When current comes in discrete packages: Viennese scientists unravel the quantum properties of the carbon material graphene
In 2010 the Nobel Prize in physics was awarded for the discovery of the exceptional material graphene, which consists of a single layer of carbon atoms...
24.05.2016 | Event News
20.05.2016 | Event News
19.05.2016 | Event News
27.05.2016 | Awards Funding
27.05.2016 | Life Sciences
27.05.2016 | Life Sciences