PAS enters an entirely new era of space research

For the first time, synchronous observation of gravitational waves and light within a single event was achieved. A Polish team of scientists and the European detector Virgo contribute to the research.

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Joint LIGO-Virgo and multi-messenger telescope observations initiate an entirely new era of space research:
- a new method of measuring distance in space and determining the rate  of expansion of the universe has been developed,
- the densest matter in the universe has been analysed – neutron star core,
- gravitational theory and the method of measuring the speed at which gravitational waves propagate – they propagate at lightspeed
- the observed remnants from the collision explain the origin of metals heavier than iron – for example, gold and platinum found on the Earth are a result of a clash of neutron stars.

The gravitational waves registered by the global network of LIGO and Virgo detectors originate from a system of two neutron stars, which spun around each other increasingly close and fast, until they collided. The collision was accompanied by an immense amount of very energetic gamma radiation, called short gamma-ray burst. Being the brightest catastrophes in space, such events have been known to astronomers for over 50 years, but the observation presented today is the first to confirm that they resulted from the collision of neutron stars. Observations gathered by the European Virgo detector allowed for the precise locating of the source of radiation. As a result, various types of telescopes could observe the collision in visible light, X-ray, radio etc.

The newest detection of gravitational waves, presented today, originated from a new type of source – a double neutron star system. Neutron stars are the most extreme and the densest objects known to science (one teaspoon of neutron star matter weighs more than all people populating the Earth). They emerge from supernova explosions, which compress matter to a density impossible to obtain or study on Earth.

Gravitational wave detectors – LIGO (USA) and Virgo (a European project, in which the Polish group POLRAW participates) – register waves emitted by distant cosmic catastrophes. They are several kilometers long laser interferometers – extraordinarily accurate “rulers” – using laser light to detect the smallest changes of distances in the space surrounding them. LIGO and Virgo projects collaborate to jointly detect and analyse data. Until now, their teams have registered 4 events involving the merger of two black holes, forming one larger, spinning black hole. Black hole collisions can only be detected by observing gravitational waves. Thanks to LIGO and Virgo detectors, scientists can “hear” events that cannot be seen.

Gravitation is one of the four fundamental interactions known to physics. Despite the fact that we experience it in our daily lives, its nature is the least thoroughly studied among the four interactions. Observing the space allows for tracking processes in giant gravitational fields (which cannot be imitated on Earth). That gives hope for understanding the fundamental principles of gravitation.

The general theory of relativity by Einstein has been a very effective theory of gravity. It implies that masses curve space around them, changing the flow of time. The motion of bodies results in ripples and vibrations in spacetime. Gravitational waves are caused by changes in distance and the flow of time in spacetime.

The conference on gravitational waves held on 16 October 2017 in Warsaw was opened by Prof. Paweł Rowiński, PAS Vice-President.
Participants of the scientific panel:
Virgo-Polgraw group:
     Prof. Andrzej Królak, Institute of Mathematics, PAS & National Centre for Nuclear Research
     Assoc. Prof. Michał Bejger, Copernicus Astronomical Center, PAS
     Prof. Tomasz Bulik, University of Warsaw
     Assoc. Prof. Dorota Gondek-Rosińska, University of Zielona Góra
     Prof. Piotr Jaranowski, University of Białystok
Prof. Rafał Moderski (HESS), Copernicus Astronomical Center, PAS
Assoc. Prof. Jacek Niemiec (HAWC), Institute of Nuclear Physics, PAS
Assoc. Prof. Łukasz Stawarz (Fermi), Jagiellonian University
Assoc. Prof. Łukasz Wyrzykowski (ePESSTO, SALT), University of Warsaw
Prof. Henryk Wilczyński (Pierre Auger), Institute of Nuclear Physics, PAS
Prof. Aleksander Żarnecki (Pi of the Sky), University of Warsaw

The conference was closed by Prof. Krzysztof Belczyński of Copernicus Astronomical Center, PAS.