Max Planck Partner Group starts work in Brazil

Close cooperation between the Albert Einstein Institute and the Federal University of ABC in Santo André.

May 27, 2010

The Max Planck Society together with the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) has established a Partner Group on “Astrophysics of compact stars” that will be funded yearly with 20,000 euros and is set to commence work as of 1 June. The head of the new Partner Group is Prof. Cecilia Chirenti.

Background information

In the past several years, groundbreaking progress has been achieved in the area of numerical relativity, and the predictions concerning gravitational wave signals from various sources have become increasingly precise. AEI scientists are among the leading international research groups in this area and, in cooperation with the newly-established Partner Group in Brazil, want to now expand their efforts to also include simulations of individual neutron stars.

Detection of gravitational waves
The direct detection of gravitational waves - tiny ripples in space-time as predicted by Albert Einstein - remains to be one of the most important unanswered questions in contemporary science. Their direct observation will usher in the era of gravitational wave astronomy and enable new insights into our universe. With the help of gravitational waves it will become possible to look back at the first trillionth of a second of the universe and also solve many mysteries concerning the birth of the universe. Previous observation methods have been bared from attaining these insights.

The observation of gravitational waves has, in addition to the corroboration of the general theory of relativity, far-reaching consequences: for the first time it will be possible to take a look into the “nursery” of the universe. The observation of the heavens carried out to date has been namely limited to the electromagnetic spectrum (e.g. radio and X-ray telescopes, and observations of visual light). Information that is accessible to us concerning the birth of the universe only reaches back a maximum of 380,000 years after the Big Bang. Times that lay further in the past have remained inaccessible up to now, as the universe first became transparent for electromagnetic radiation from this point in time. The various theories focusing on the early universe have thus remained experimentally unconfirmed. The direct measurement of gravitational waves is set to open up completely new possibilities, as it will most likely become possible to “listen in on” the first trillionth of a second following the Big Bang. With gravitational wave astronomy, we will have access to completely new areas of science.

Status of the gravitational-wave observatories that are up and running
Currently, there are several gravitational wave detectors of the first generation active in Europe: The German-British GEO600 observatory near Hannover is operated by the AEI Hannover; the French-Italian-Dutch Virgo Project is located in Cascina near Pisa. The data from these detectors are combined with the data from the three American LIGO interferometers. The entire data pool is currently being searched for gravitational wave signals from astrophysical systems.

In addition, work has begun on upgrading the interferometric gravitational wave detectors ("second generation"). The sensitivity of Virgo and LIGO in the lower frequency ranges (up to one kilohertz) will increase tenfold through the use of innovative technologies that have partially been developed in Europe. GEO600 will carry out, in particular, groundbreaking work in the broadband observation of higher frequencies, here as well thanks to the development and deployment of new technologies. GEO600 is considered to be the think tank of gravitational wave research.

Neutron stars
Neutron stars, in addition to black holes, are some of the most fascinating objects in the universe. As the end result of stellar evolution and remains of a supernova explosion, neutron stars have a mass that is somewhat bigger than the mass of the Sun (ca. 1.4 solar masses) which, however, is compacted to a perfect sphere that is as large as a small town with a radius of 10-12 kilometres. They are made up almost entirely of core matter, primarily of neutrons, which exhibit extreme behaviour in several respects. For example, their density is so high that a teaspoon of neutron star matter would weigh as much as the entire Alps. At the same time, the gravitational forces are so strong, that the physical conditions are very similar to those in the vicinity of a black hole of comparable mass. Understandably, such conditions cannot be created in laboratories on Earth; this is why we still know so little about these interesting bodies.

The inner structure of neutron stars
We receive a good part of our knowledge about the size and mass of neutron stars through satellite observations in the X-ray and gamma ray area. The measurements also provide us with information about the behaviour of these compact objects in binary systems (so-called double-star systems) in which they suck matter from their partner star. As we receive this information from electromagnetic signals, we learn nothing however about the inner structure of neutron stars, but rather only about their surface.

In future, electromagnetic signals will not be our only source of information about neutron stars. It is a known fact that binary neutron stars emit energy in the form of gravitational waves. For their long-term observation of the binary pulsars PSR 1913+16, through which the emission of gravitational waves was indirectly verified, Russell A. Hulse and Joseph H. Taylor were awarded the Nobel Physics Prize in 1993. Such binaries are one of the strongest sources of gravitational waves and should actually be able to be measureable with today’s detectors - on the condition that they are close enough. Gravitational waves, in contrast to electromagnetic rays, will also provide us with information about the interior of neutron stars. The gravitational wave signal of a neutron star can, without exaggeration, be called the ‘Rosetta stone’ for the decoding of its inner structure.

Max Planck Partner Groups
Scientific Partner Groups of the Max Planck Society (Max Planck Partner Groups) can be established in partnership with a research institute abroad, when an outstanding junior scientist, after a research residency at a Max Planck Institute, returns to a professional laboratory of his/her home country and carries out research there that is also in the interest of the former hosting Max Planck Institute. Partner Groups are thus intended to establish a sustainable bond between Max Planck Institutes and the former guest scientist from abroad. To this effect, the Max Planck Society makes available in individual cases and upon special application 20,000 euros annually and per Partner Group.

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