Astroparticle physics is a field of science that studies elementary particles arriving to us from space. This is a relatively young discipline that emerged at the intersection of particle physics and modern sciences about space, such as astrophysics, astronomy, and cosmology.
In astroparticle physics, scientists collect data on various elementary particles of cosmic origin using detectors on Earth and in space. Analysis of the collected data allows us to draw conclusions about space objects, make new discoveries and learn more about our universe.
What are messengers?
There are several types of radiation that deliver us information on what happens in the outer space. Such phenomena are called messengers.
Messengers include cosmic rays, gamma rays, neutrinos and gravitational waves. Dark matter can also be considered a potential messenger, however, this messenger has never been experimentally registered yet.
What is multimessenger astronomy and what do we need it for?
Studying the phenomena with the help of several messengers at the same time (one can say “using several channels”) allows us to get a more comprehensive picture of complex phenomena occurring in space and confirm or disprove the hypotheses explaining them. This way of studying space objects is called multimessenger astronomy (MMA).
The first steps towards multimessenger astronomy have been taken in 1967, when the solar neutrino flux was registering at the Brookhaven Solar Neutrino Experiment. The resulting lack of detected neutrinos compared to theoretical predictions has later led to the experimental confirmation of neutrino oscillations.
One can consider February 23, 1987 to be the date of birth of extrasolar multimessenger astronomy. This day, neutrino, gamma-ray, and x-ray fluxes were recorded in addition to the optical flare for the supernova SN 1987A.
An important milestone in the development of multimessenger astronomy is 2017, when the fusion of neutron stars was observed simultaneously:
- through gravitational waves at the LIGO-Virgo observatory
- with electromagnetic radiation in various ranges with the Fermi space telescope
- using the neutrino by IceCube laboratory
- in the X-ray range by the Swift space laboratory.
This event helped scientists to prove that short gamma-ray bursts are associated with fusions of neutron stars, confirm that the propagation speed of gravitational waves is equal to the speed of light, check the General Relativity one more time, specify the Hubble constant, and also better understand the structure of neutron stars. The very important result is the discovery that most of the heavy elements in space (and on Earth), such as gold, silver, uranium, etc., were produced not during supernova explosions, but during fusion of neutron stars. The simultaneous observations using several messengers made it possible to register the fact of the merger, construct its theoretical model and calculate the intensity of the formation of heavy elements.