Israelis find ‘marker’ for Einstein’s ripples

New Worlds: Scientists still searching for gravitational waves in space-time fabric considered the "sounds" of the universe.

Albert Einstein 311 (photo credit: Al. Aumuller / Library of Congress)
Albert Einstein 311
(photo credit: Al. Aumuller / Library of Congress)
Nearly a century after Albert Einstein wrote about gravitational waves – small ripples in the fabric of space-time considered to be the “sounds” of the universe – scientists are still searching for them. Advanced gravitational wave detectors are being built in the US, Europe, Japan and Australia, and are scheduled to become operational in 2015. But the task is daunting; there are competing sources of “noise” that make it difficult to establish the source of any wave detected.
As a result, astronomers have for a long time been seeking a potential electromagnetic “marker” signal appearing with or after some gravitational waves. Such a marker would make it possible to verify the connection between detected gravitational waves and specific astronomical events.
In their new article published recently in Nature, Prof. Tsvi Piran of the Hebrew University of Jerusalem and Dr. Ehud Nakar from Tel Aviv University wrote that they had actually managed to identify such a marker. Nakar and Piran noted in their article that an unidentified transient radio signal observed in 1987 by Dr. Jeffrey Bower and colleagues has all the characteristics of such signal, and thus may in fact have been the first direct detection of a neutron binary star merger in this way.
They noticed that surrounding interstellar material would slow debris ejected at velocities close to the speed of light during the merger of two neutron stars. Heat generated during this process would be radiated away as radio waves. The resulting strong radio flare would last a few months and be detectable with current radio telescopes from a billion light years away.
While any moving mass produces gravitational waves, a signal loud enough to be detected requires the motion of huge masses at extreme velocities. The prime candidate sources are mergers of two neutron stars – two bodies, each with a mass comparable to the mass of our sun. Such events are thought to take place only once in hundreds of thousands of years per galaxy. Thus to detect a signal within our lifetime, the detectors must be sensitive enough to detect signals out to distances of a billion light years away from Earth. This poses an immense technological challenge. At such distances, the gravitational wave signal would sound like a faint knock on our door when the TV set is turned on and the phone is ringing.
Search after such a radio signal would certainly take place following a future detection, or even a tentative detection of gravitational waves. However, even before the advanced gravitational wave detectors become operational, as expected in 2015, radio astronomers are prepared to look for these unique flares.
Twenty-six science teachers have completed advanced studies in the Rothschild-Weizmann Program for Excellence in Science Teaching and will be awarded M.Sc. degrees in science teaching from the Weizmann Institute’s Feinberg Graduate School in Rehovot. This program – the first of its kind in Israel – is designed for high-school science teachers. In the upcoming year, about 100 will be enrolled in the two-year program.
It is based on the belief that the best way to improve science education is to train excellent teachers. Thus, the Rothschild-Weizmann Program invites top science teachers to participate. In cooperation with Weizmann Institute scientists, an intensive study program was put together in which the students deepen their knowledge in all fields of science, meet with scientists and visit their labs, learn about the latest scientific advances, gain new approaches to teaching, participate in institute research on science education and have the opportunity to lead new educational initiatives.
The Rothschild-Weizmann Program, supported by the Caesarea Edmond Benjamin de Rothschild Foundation, was established three years ago. Heading the program are Prof. Shimon Levit of the faculty of physics and Prof. Bat Sheva Eylon, head of the science teaching department.