Observations of an unusual family of stars, which are home to one pulsar and two white dwarfs, helped scientists to prove that gravity slows down the flow of time and bends space exactly as predicted by Einstein's theory of relativity.
“We asked the question 'How does the source of gravity fall?' This may sound strange to an uninformed public, but from Einstein's point of view, both mass and energy are one and the same thing. If the principle of equivalence is violated, then the accumulations of energy surrounded by a powerful gravitational field will accelerate during the fall in a completely different way than a similar bunch of energy outside it,”says Anne Archibald from the University of Amsterdam (Netherlands).
Archibald and her colleagues spoke at the annual conference of the American Astronomical Society in Washington last week. They talked about how they managed to use observations of the unique star system J0337 + 1715 in the constellation Taurus for the toughest and most accurate test of the so-called principle of equivalence - one of the foundations of Einstein's general theory of relativity.
This principle, in its most general and simplified form, states that particles of light of different wavelengths emitted by a distant object in space must arrive at the Earth at the same time, even if they have passed through powerful gravitational fields. Other objects of the visible world should behave in a similar way, starting with balls and fluffs in Galileo's experiments and ending with lumps of energy.
The principle of equivalence has already been repeatedly tested both on Earth and in orbit using the American Gravity Probe A probe, the Russian Radioastron and a pair of European Galileo satellites. On the other hand, scientists are not yet completely sure whether it is observed in the most extreme corners of space - in the "families" of neutron stars or in the vicinity of black holes.
Archibald and her colleagues carried out the first such test by observing a kind of gravitational "matryoshka", a system of three "dead stars" - one pulsar and two white dwarfs.
One of the white dwarfs and the pulsar revolve around each other at such a small distance that they generate yet invisible to us, but powerful enough gravitational waves. The situation is further complicated by the second white dwarf moving around the first two stars and periodically obscuring their light.
This arrangement of this star system allowed scientists to check whether Einstein was right. The fact is that if the principle of equivalence was not observed and objects with a more powerful gravitational field "fell" faster than their neighbors, then the pulsar's orbit would be curved in a certain way, stretching towards a more distant white dwarf and moving in a circle with it …
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These curvatures, in turn, could be noticed by how strongly the pulsar signals are delayed at different times, when it is supposedly located at different points of its elongated orbit. Guided by this idea, scientists observed J0337 + 1715 using the American GBT radio telescope and the Gemini optical telescope in Hawaii.
As these observations showed, the signals from the pulsar reached the Earth at approximately equal intervals of time, which confirmed Einstein's theory with a still record high measurement accuracy, exceeding previous records by 50-100 times.
A similar result, as astronomers note, once again does not allow physicists to understand how the contradictions between the theory of relativity and quantum physics can be eliminated, which is necessary to explain what happens inside black holes and understand how the universe will develop in the future.
