It has not yet been possible to measure the gravitational waves predicted by Einstein's theory of general relativity. They are so weak that they get lost in the noise of the measurements. But thanks to the latest simulations of the merging of binary neutron star systems, the structure of the sought-after signals is now known. As a team of German and Japanese theoretical astrophysicists reports in the Editor’s choice of the current edition of the scientific journal "Physical Review D", gravitational waves have a characteristic spectrum that is similar to the spectral lines of atoms.
Gravitational waves are generated when masses accelerate. The first indirect evidence for their existence was detected in 1974 when the binary pulsar PSR B1913+16 was discovered in the constellation Aquila.
The two rapidly rotating neutron stars are drifting towards each other in a spiral shape, which is why, the astrophysicists explain, they are losing energy and emitting gravitational waves. Russell A. Hulse and Joseph H. Taylor received the 1993 Nobel Prize in Physics for this discovery.
In the meantime, there are now several large-scale experiments for detecting gravitational waves: the American LIGO experiment, the European Virgo experiment, and the Japanese KAGRA detector.Experts estimate that signals of gravitational waves from merging binary neutron star systems will be detected within the next five years.
"These signals are not easy to detect, because they have an extremely small amplitude." But despite these difficult conditions, it is possible to find them, if you know what to look for in advance," explained Professor Luciano Rezzolla from the Institute for Theoretical Physics at Goethe University.
Together with a Japanese colleague from Osaka University, he has studied a number of binary neutron star systems with the help of the latest simulation techniques and has discovered that the merging of the stars generates characteristic gravitational wave spectra. "These spectra correspond, at least logically, to the electromagnetic spectral lines emitted by atoms or molecules. From these we can derive information on the characteristics of the stars," explains Rezzolla.
As the astrophysicists show in two publications with related content in "Physical Review Letters" (published in November 2014) and in the current edition of "Physical Review D," the gravitational waves spectrum is like a fingerprint for the two stars. If scientists learn how to interpret these spectra, they will know what the neutron stars are made of and will be able to determine what is their equation of state, which is so far unknown.
Equations of state describe the thermodynamic properties of systems as a function of variables, such as pressure, temperature, volume, or particle number. To this Rezzolla adds: "This is a very exciting possibility, because then we would be able to solve a riddle that has remained unsolved for 40 years: What are neutron stars made of and what is their stellar structure?"
"If the signal is strong and thus the fingerprint is very clear, even a single measurement would be sufficient," Rezzolla predicts. "The prospects of solving the riddle of neutron stars have never been this good. The gravitational waves that we hope to detect in a few years are already on their way from the farthest reaches of the universe."
K. Takami, L. Rezzolla, and L. Baiotti, Constraining the Equation of State of Neutron Stars from Binary Merger, Phys. Rev. Lett. 113, 091104 (2014).
K. Takami, L. Rezzolla, and L. Baiotti, Spectral properties of the post-merger gravitational-wave signal from binary neutron stars, Phys. Rev. D. 113, 091104 (2015), 2. März 2015.
Information: Prof. Luciano Rezzolla, Institute for Theoretical Physics, Campus Riedberg, Tel.: (069) 798-47871, email@example.com.
Goethe University is a research-oriented university in the European financial centre Frankfurt Founded in 1914 with purely private funds by liberally-oriented Frankfurt citizens, it is dedicated to research and education under the motto "Science for Society" and to this day continues to function as a "citizens’ university". Many of the early benefactors were Jewish. Over the past 100 years, Goethe University has done pioneering work in the social and sociological sciences, chemistry, quantum physics, brain research and labour law. It gained a unique level of autonomy on 1 January 2008 by returning to its historic roots as a privately funded university. Today, it is among the top ten in external funding and among the top three largest universities in Germany, with three clusters of excellence in medicine, life sciences and the humanities.
Publisher The President of Goethe University, Marketing and Communications Department, 60629 Frankfurt am Main
Editor: Dr. Anke Sauter, Science Editor, International Communication, Tel: +49(0)69 798-12498, Fax +49(0)69 798-761 12531, firstname.lastname@example.org
Dr. Anke Sauter | idw - Informationsdienst Wissenschaft
Smallest transistor worldwide switches current with a single atom in solid electrolyte
17.08.2018 | Karlsruher Institut für Technologie (KIT)
Protecting the power grid: Advanced plasma switch for more efficient transmission
17.08.2018 | DOE/Princeton Plasma Physics Laboratory
There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.
The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...
New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
17.08.2018 | Event News
08.08.2018 | Event News
27.07.2018 | Event News
20.08.2018 | Information Technology
20.08.2018 | Life Sciences
20.08.2018 | Information Technology