Observing gravitational waves is already beginning to be a real possibility. That has been the conclusion of the presentation of the LISA Pathfinder mission, of the European Space Agency (ESA), held at the European Space Astronomy Center (ESAC). In the tests, the technological tools that will be used to carry out a future mission to detect gravitational waves from space have been used. The trial has been a success. According to Favio Favata, head of ESA’s Science Directorate Coordination Office, Europe has taken a leap in quality to a much more innovative and advanced level.
After only two months of scientific work, expectations have been exceeded and a precision five times higher than expected has been achieved: the two cubes housed in the ship are in free fall, under the exclusive influence of gravity and without being subjected to any other external force. In a paper published in Physical Review Letters , the LISA Pathfinder team reveals that the masses under test are virtually immobile relative to each other, accelerating less than one ten billionth of Earth’s gravity. The realization that the key technologies of the mission work opens the door to the development of a large space observatory , capable of detecting gravitational waves from a wide variety of distant and exotic objects in many regions of the Universe.
Predicted by Albert Einstein a century ago, gravitational waves are ripples in the space-time fabric that move at the speed of light and are caused by the acceleration of massive objects. They can be generated, for example, by supernovae, binary sources of neutron stars spinning around each other, and pairs of emerging black holes.
However, even starting from these extremely powerful objects, by the time these space-time fluctuations arrived on earth, they practically disappeared, reducing to less than one hundred billionth.
Very advanced technologies are required to record these tiny changes, so gravitational waves were not detected directly for the first time until September 2015 , when they were captured by the Gravitational Wave Laser Interferometry Observatory (LIGO). During this experiment the characteristic signal of two black holes, each with a mass about 30 times that of the Sun, was seen spinning as they approached during the final 0.3 seconds before joining together to form a single, more massive object.
The signals detected by LIGO have a frequency of about 100 Hz, but gravitational waves spread over a much larger spectrum. In particular, the lower frequency oscillations are associated with even more exotic events, such as the merger of supermassive black holes. With masses up to billions of times greater than that of the Sun, these giant black holes are at the center of massive galaxies . When two galaxies collide, these black holes eventually converge, expelling large amounts of energy in the form of gravitational waves throughout the process, which reach their maximum in their last minutes of existence.
