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The birth of Multimessenger Astronomy – Photonick

By CoperNick

Angela Pastore 

 

February 26, 2019

 

Multimessenger Astronomy is a new way of exploring the universe, and aims for globally coordinated observations of cosmic rays, neutrinos, gravitational waves, and electromagnetic radiation across a broad range of wavelengths. This is expected to yield crucial information on the mechanisms behind the most powerful astrophysical sources.

The birth of Multimessenger Astronomy was announced on October 16, 2017, following the first observation of a gravitational wave generated by the fusion of two neutron stars, by the INFN interferometer and the French CNRS, Virgo near Cascina (Pisa), and the two U.S. interferometers LIGO. A few moments later, the telescopes for electromagnetic radiation picked up the photons (from radio waves to gamma rays) associated with the powerful explosion that occurred during this phenomenon, occurring 130 million light years away on the outskirts of the galaxy NGC4993. Last July, the second multi-message observation was announced, this time thanks to the discovery of a cosmic neutrino in association with high-energy photons, which were traced back to their source: a “blazar”, that is an active galaxy with a supermassive black hole in the center, 4.5 billion light years away in the direction of the Orion constellation.

 

Credit: Dana Berry/Skyworks Digital Inc.

Let’s try to explain what these messengers are and how they work. When we look at the sky we see the light of the stars that form our galaxy: that light represents a “messenger”, which brings us information about what happened many years ago, somewhere in the galaxy. In Physics the concept of messenger plays a double role: in Physics of the Infinitely Small (Particle Physics) fundamental interactions’ behaviour is manifested through the exchange of messenger particles, which depend on the type of force we are considering; for Physics of the Infinitely Large (Astrophysics and Cosmology) the cosmic messengers are those signals of various kinds (electromagnetic radiation, cosmic rays, neutrinos, gravitational waves) that bring us information about phenomena and events that occur very far from us. These messengers are key in allowing us to investigate the cosmos because, given the huge distances, we cannot go and see what happens near a supernova, a black hole or inside another galaxy. Particles can, therefore, play the role of “cosmic messengers”. Through these cosmic messengers it is possible to access phenomena that would never be replicable in the laboratory, and this allows us to understand the physical world and its laws in depth. Today we are able to observe all cosmic messengers which are stable enough to reach us: photons, neutrinos,
electrons and positrons, stable atomic nuclei, and of course gravitational waves.

 

Credit: NASA

Modern observational capabilities enable us to have access to the entire spectrum of electromagnetic radiation, from radio waves, to infra-red, visible, ultraviolet emission, to X-rays and finally to super-energetic gamma rays. Each of these frequencies tells us a part of the history of our universe and lets us investigate in detail the functioning of all those mysterious systems that constitute it; from this kind of study we can extend to the “multimessenger” study. For a couple of years now, gravitational waves have been added to the list of messengers, and the universe seen through them give us the chance to observe phenomena that otherwise we would not be able to see directly, such as the fusion of two black holes.

The observation of the fusion of two neutron stars in the entire multimessenger spectrum that took place last year by combining all available observation channels is the result of a very long journey that physicists and astrophysicists have undertaken. This research has led to the development of techniques capable of observing the universe in all its nuances and, at the same time, it represents the beginning of a new era in the study of the universe that will yet lead to many new discoveries.

                                                                                                                   

 

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