Scientists believe that the Earth has been hit by a massive explosion of energy in the past. The energy detected by the instruments of a space probe could have come from the dramatic collision of two dense neutron stars that merged together before collapsing into a black hole

Gamma rays

By examining the archive records of short bursts of gamma rays in the database of a space mission, researchers have found these signals. The Earth was hit by a massive explosion of energy detected in the experimental data of a space probe. Probe orbited around our planet two decades ago, and recorded strong energy fluctuations due to two gamma ray bursts. The frequency of the signals suggests that the bursts came from two neutron stars that were merging. This discovery could be the key to changing our understanding of the cosmological physics underlying these bizarre phenomena.

Neutron stars have masses greater than the Sun, but are usually no larger than a small city, according to Paul D. Lasky, associate professor at the School of Physics and Astronomy at Monash University. In the article published in Nature (ref.), the professor states that given the density of these stars, when they collide, unpredictable and unexpected effects are obtained.

The collision can sometimes form a massive neutron star, known as a hypermassive star. This new star usually collapses into a black hole under its own enormous gravity. Observations of these events have been recorded for decades, but we are looking for these phenomena in another way. Simulations, however, suggest that hypermassive stars could be detected by typical gamma ray bursts that are emitted after collisions.

Gamma-ray Observatory

Researchers led by University of Maryland scientist Cecilia Chirenti examined 700 observations of gamma rays in the archives in the hope of finding these characteristic bursts. During their research, they found signals from two bursts that matched the search criteria. The explosions, named GRB 910711 and GRB 931101B, had the correct tone of oscillations emitted by two neutron stars colliding.

The signals were both found in the archive data of the Burst and Transient Source Experiment (BATSE). Mission was tasked with monitoring gamma rays on board the Gamma-Ray Observatory launched in April 1991. The probe operated in low earth orbit and studied explosions until 2000, when NASA concluded its mission.

Scientists hope that the results, published in Nature and reported in a paper entitled “Kilohertz quasi-periodic oscillations in short gamma-ray bursts”, can lead to a new way of studying neutron stars and their collisions. This could mean that researchers in the near future will no longer need to observe gravitational waves, which are rare, to detect these cosmic phenomena.

Stefano Gallotta
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