The Department of Astronomy and Astrophysics (DAA) of Universitat de València, managed by José Antonio Font, actively participates in computational model of astrophysical and cosmological gravitational radiation sources through the scientist groups “Computational Astrophysics and Cosmology” (COMPAC) and “Computer-Aided modelling in Astrophysics” (CAMAP). The detection of gravitational waves, announced this Thursday in Washington is the result of a multidisciplinary international collaboration.
Among the most important results of COMPAC and CAMAP can be mentioned the getting of a stellar collapse gravitational radiation catalogue, used data analysis groups of interferometric detectors with a view to designer filters and methods to facilitate the detection. In addition, radiation patterns of stellar collapse magnetized in neutron stars or black holds formation in collapse theories of gamma rays eruptions have been obtained. Researchers from mentioned groups study, moreover, gravitational radiation emitted in the collision of neutron stars in binary systems, in accretion disks around black holes, in pulsar relativistic stars in rotation, and in galaxies collision. Members of DAA are part of Gravitational Waves Thematic Network “Redongra”, funded by MINECO, together with other 8 national universities, among which is the Universitat de les Illes Balears, the only national one which participates in LSC and two of its representatives appear in the article that detail the discovery.
As well, it can be pointed that the DAA manager is an elected member of the board of directors of VESF (Virgo-EGO Scientific Forum), forum constituted to the scientist development around the interferometric Virgo.
This Thursday, 11 February, at 16:30 local time, representatives from scientist collaboration LSC (LIGO Scientific Collaboration; LIGO is the acronym of Laser Interferometer Gravitational-wave Observatory), get together in National Science Foundation headquarters (Washington, EE.UU.) to announce the gravitational waves detection, a scientist achievement without precedents. The detected signal comes from two black holes collision of 29 and 36 solar masses. During the collision, 3 solar masses were emitted by gravitational waves.
The detection announcement has coincided with the publication of the scientist article in Physical Review Letters. With this detection is not only confirm, after decades of research, the existence of gravitational radiation, but the existence of black holes too. It does not seem exaggerated to say we can stand before the century discovery.
With all due caution, temporally and technological, the discovery announced yesterday is comparable to the first astronomic observations of Galileo, in 1609, with a telescope made by himself. Theses observations changed our global view and deserved to be commemorated with the proclamation (by UNESCO) of the 2009 year as a an International Year of Astronomic .
Gravitational waves were predicted by Albert Einstein on his general theory of relativity whose announce turns this year its first century. These waves are interpreted as tissue waves of space-time generated in astrophysics and cosmologic scenes in which converge violent dynamics, with speeds similar to the light ones, as well as ultra-intense gravitational fields, in which the acceleration of gravity is billions of times bigger that the one of our Sun surface. (Which, in turn, is thousand times bigger than Earth surface) Extremely enough, these conditions regularly occur in scenes characterized by the presence of the named compact objects, such as white dwarf, neutron stars and, particularly, the black holes, the ones which have a stellar origin and those supermassive black holes which exist in galaxies nucleus.
The detection announced yesterday have been achieved by using an experimental device named interferometric of Michelson-Morley, which uses the physics property that a gravitational waves produces tidal forces in any object. To the transition of a gravitational wave, relatives variations in positions of masses detector are analysed by the study of the light path itinerary along the two arms of the device. The change (infinitesimal) in the distance that is gone over by the laser origins a change in the intensity of the light observed at the detector exit. The laser interference pattern moves from being destructive (when there is not a wave) to constructive (when a wave passes). To detect a gravitational signal with these kind of devices is a challenge equivalent to measure a variation lower than the size of an atomic nucleus in a astronomical unit. For this reason a long time has been spent to detect them. Until yesterday announcement, they were just “detected” indirectly in connection with the discovery in 1974 of the binary pulsar PRS 1913+16 by the radio astronomics Russell Hulse and Joseph Taylor (both awarded with the Nobel Prize of Physics in 1993).
The discovery has been realised in the American interferometric Advanced-LIGO, which consists on two detectors separated by among 3000 km, one locates in Livingston, Louisiana and the other in Hanford, Washington.
In addition, there are observatories of gravitational waves in Europe, GEO600 in Hannover (Germany) and which is part of the LSC, and VIRGO closed to Pisa (Italy), besides the one in Japan KAGRA (under construction). There are studies about the design of third generation detectors in Europe too (Einstein Telescope) and the special detector eLiSA which has an assigned launch date in 2034 as a mission L3 of ESA. Moreover, the satellite LISA Pathfinder, the prototype to measure the success possibilities of eLISA mission and that has Spanish participation (IEEC), was on-orbit last 2 December 2015. Without any doubt, we are attending to the birth of the gravitational radiation astronomy, and the announcement of its detection is going to contribute to promote enormously this area research.
The experimental result announced yesterday could not be possible without a international theoretical effort, leaded by the Numerical Relativity, discipline of General Relativity dedicated on the research of number solutions of Einstein equations through super computers simulations. Since the beginning, (last 60s), the Numerical Relativity has produced gravitational radiation signal patterns with which make the detection of real signals easy because, due to their small amplitude, they are completely hidden by the detector noise. The Numerical Relativity has got to resolve the formation of black holes as a result of gravitational collapse of massive stars and the collision of compact objects in binary neutron stars or black holes. This last example, the problem of tow bodies in General Relativity, could be solved in 2006. The wave train of gravitational radiation obtained in numerical solutions is characterized by the presence of a singla type “chirp” (a sine wave which increases in frequency and amplitude as two black holes are bringing closer), followed by a type signal called “burst” when two black holes join, to end find a type signal “ringdow” which belongs to the exponential decline of the amplitude of the oscillations of final black hole. It is important to say that this signal unique in black holes binaries fully coincides with the detected signal by Advanced-LIGO.
If Galileo’s telescope was precursor of current astronomic observatories (terrestrial and in space) and its observations opened the electromagnetic window to Universe observation, the occurrence announced yesterday Thursday 11 February means, without any doubt, the opening of the gravitational window to observe the Universe. A new cosmos is going to appear in the eyes of gravitational waves observatories, complementing the enormous amount of information received in the whole electromagnetic spectrum and the one we will received, in a near future, by neutrinos telescopes. New generations of young researchers are claimed to participated in this new scientist adventure: Universe observations through gravitational waves.
The historical discovery announced yesterday shows, like in other precedents occasions, that Einstein was right again. As the physics and journalist Marcia Bartusiak has said, the unfinished Einstein symphony has just been ended.
Links:
https://ligo.caltech.edu/
Advanced LIGO https://www.advancedligo.mit.edu/
Virgo: https://www.ego-gw.it/public/virgo/virgo.aspx
eLISA: elisascience.org
LISA Pathfinder :http://sci.esa.int/lisa-pathfinder/
VESF: https://www.ego-gw.it/public/vesf/vesf.aspx
Last update: 12 de february de 2016 07:57.
News release
