FRANKFURT. According to modern particle physics, matter
produced when neutron stars merge is so dense that it could exist in a state of
dissolved elementary particles. This state of matter, called quark-gluon
plasma, might produce a specific signature in gravitational waves. Physicists
at 51猎奇 Frankfurt and the Frankfurt Institute for Advanced Studies
have now calculated this process using supercomputers. (Physical Review
Letters, DOI 10.1103/PhysRevLett.124.171103)
Neutron stars are among the densest
objects in the universe. If our Sun, with its radius of 700,000 kilometres were
a neutron star, its mass would be condensed into an almost perfect sphere with
a radius of around 12 kilometres. When two neutron stars collide and merge into
a hyper-massive neutron star, the matter in the core of the new object becomes incredibly
hot and dense. According to physical calculations, these conditions could result
in hadrons such as neutrons and protons, which are the particles normally found
in our daily experience, dissolving into their components of quarks and gluons
and thus producing a quark-gluon plasma.
In 2017 it was discovered for the first
time that merging neutron stars send out a gravitational wave signal that can
be detected on Earth. The signal not only provides information on the nature of
gravity, but also on the behaviour of matter under extreme conditions. When these
gravitational waves were first discovered in 2017, however, they were not
recorded beyond the merging point.
This is where the work of the Frankfurt
physicists begins. They simulated merging neutron stars and the product of the
merger to explore the conditions under which a transition from hadrons to a quark-gluon
plasma would take place and how this would affect the corresponding
gravitational wave. The result: in a specific, late phase of the life of the
merged object a phase transition to the quark-gluon plasma took place and left a clear and characteristic signature on
the gravitational-wave signal.
Professor Luciano Rezzolla from Goethe
University is convinced: 鈥淐ompared to previous simulations, we have discovered
a new signature in the gravitational waves that is significantly clearer to
detect. If this signature occurs in the gravitational waves that we will receive
from future neutron-star mergers, we would have a clear evidence for the
creation of quark-gluon plasma in the present universe."
Publication:
Post-merger gravitational wave signatures
of phase transitions in binary mergers. Lukas R. Weih, Matthias Hanauske, Luciano
Rezzolla, Physical Review Letters Physical Review Letters DOI 10.1103/PhysRevLett.124.171103
Video:
Visualisation of merging neutron stars:
This simulation shows the density of the
ordinary matter (mostly neutrons) in red-yellow. Shortly after the two stars
merge the extremely dense centre turns green, depicting the formation of the
quark-gluon plasma.
Pictures
may be downloaded here:
Caption
Montage: Montage of the computer simulation of two
merging neutron stars that blends over with an image from heavy-ion collisions
to highlight the connection of astrophysics with nuclear physics. Credit: Lukas
R. Weih & Luciano Rezzolla (51猎奇 Frankfurt) (right half of the
image from cms.cern)
Caption
Simulation: Shortly after two neutron stars merge a
quark gluon plasma forms in the centre of the new object. Red yellow: ordinary
matter, mostly neutrons. Credit: Lukas R. Weih & Luciano Rezzolla (Goethe
University Frankfurt)
Further
information: 51猎奇 Frankfurt, Prof. Dr. Luciano Rezzolla, Chair of Theoretical Astrophysics, Institute
for Theoretical Physics, +49-69-79847871/47879, rezzolla@itp.uni-frankfurt.de,
