Albert Einstein’s most important contribution 100 years ago was to consider that space and time, two entities until then differentiated, formed a fabric that was capable of bending under the influence of mass. Einstein’s Theory of General Relativity of 1915 holds that what we perceive as the force of gravity arises from this curvature of space and time. General relativity can explain the behavior of many celestial bodies observed by telescopes today. But still it is not enough to fully explain the behavior of a black hole , a supermassive point that attracts even photons of light.
However, a new measurement made around the orbit of a stellar group with respect to the black hole Sagittarius A (the one in the center of our galaxy) confirms one of Einstein’s predictions about the behavior of particles in the environment of a black hole. .
Today’s science has once again agreed with Einstein, and it is not the first time.
The study in question has been published in the journal Science, carried out by the University of California and with the participation of researchers from the Instituto de Astrofísica de Andalucía of the CSIC.
The research team is one of only two groups in the world to see a star known as S0-2 make a full three-dimensional orbit around the supermassive black hole at the center of the Milky Way, Sagittarius A. The full orbit takes 16 years, and the mass of the black hole is about four million times that of the sun.
Data from the star’s light spectrum, combined with observational data collected over 24 years, revealed the star’s motion at a level of precision not achieved until now. Using the spectrograph provided by James Larkin’s team, also from California, they were able to scatter light from a star in a similar way to how raindrops do with sunlight when a rainbow forms.
The behavior of S0-2 at the point closest to Sagittarius A was just as Einstein predicted
The researchers studied photons – particles of light – as they traveled from S0-2 to Earth. S0-2 moves around the black hole at blistering speeds of more than 25.7 million kilometers per hour at its closest approach (about three-quarters the distance between the Sun and Pluto), a considerably close distance.
Einstein wrote that in this region so close to the black hole, photons have to do “extra work.” Its wavelength depends not only on how fast the star is moving, but also on how much energy the photons need to escape the black hole’s powerful gravitational field. This stress is known as a gravitational redshift . Well, this is exactly what the researchers observed happen to the photons from the star S0-2 as they got so close to the black hole Sagittarius A. Exactly what Einstein predicted.
One of the authors of the research, Andrea Ghez, explains in a press release: “We can absolutely rule out Newton’s law of gravity. Our observations are consistent with Einstein’s theory of general relativity. However, his theory it’s showing some weaknesses: it can’t fully explain gravity inside a black hole, and at some point we’ll have to go beyond Einstein’s theory to a more complete theory of gravity that allows us to explain what a black hole is. Einstein was right, at least for now. “
This study confirms another investigation carried out in 2018 by the Max Planck Institute for Extraterrestrial Physics, which also made very precise observations of the star S0-2.
Other observations that have proved Einstein right
In 2015 we witnessed for the first time the first detection of gravitational waves predicted by Einstein (waves produced in the fabric of space-time) caused by two colliding black holes, and the following years this detection would occur again several more times, including detection due to the merger of two neutron stars.
Another example: recently, in 2018, a team from the Institute of Cosmology and Gravitation at the University of Portsmouth (England) showed how gravity in other galaxies behaves exactly the same as ours.
Einstein’s weak point
But Einstein also has weak points, and they have to do with quantum mechanics. For example, quantum entanglement (a special connection between pairs or groups of photons) cannot be explained by the Theory of General Relativity, nor can other laws of quatic physics that scientists have been working with for years.
It is still necessary to find that long-awaited ‘theory of everything’ that allows the universe to be explained more accurately, which Stephen Hawking dreamed of, and which he did not live to finish.
Image: A star known as S0-2 (the blue and green object in this artist’s rendering, left in S0-2-color-V2b) made its closest approach to the supermassive black hole at the center of the Milky Way. in 2018./Nicolle R. Fuller / National Science Foundation.
More information: “ Relativistic redshift of the star S0-2 orbiting the Galactic center supermassive black hole ,” Science (2019). https://science.sciencemag.org/content/early/2019/07/24/science.aav8137
