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If we ask you to think of the solar system probably you might imagine a picture of the eight planets crowded very close to the Sun peacefully placed in the center, on a still dark background. But the reality is different. As we wrote before, the solar system is so vast and planets are so tiny, in comparison, that it would be impossible to be able to see them in a schema that is true to reality. On the other hand, the Sun is not still: it revolves around the galaxy at a speed of 828.000 km per hour, which takes about 225 million years to complete one full turn. If you could see the solar system from the side, it would seem that all the ensemble moves in a wonderful propeller.
But is that even the Sun is exactly in the center. The entire solar system revolves around what is known as center of gravity or barycenter, a point in which the influence of the mass of all the objects is balanced. As the Sun is not the only object that constitutes the solar system, although he only brings 99.8% percent of its mass, the center of the set does not coincide with the center of the star . In fact, the same thing happens on Earth: the Moon does not rotate around our planet; in reality, both revolve around a centre of gravity common, which is about 4,600 kilometres from the centre of the Earth.
A planet (in blue) and a star (in white) revolve around the center of gravity or barycenter, as seen from above. Astronomers can measure the pitch of stars to detect planets and to measure its mass and its orbit – https://spaceplace.nasa.gov
This week, a group of researchers has been with the precise location of the center of gravity or barycenter of the solar system. What have been achieved through the reference of a dozen of pulsars, neutron stars that spin at a very high speed and sent pulses of radiation to the Earth with such precision that serve as the authentic watches galactic. The authors are confident that their advances, that have been published in the journal “Astrophysical Journal”, having application to detect the gravitational waves that pass through the solar system and that originate from supermassive black holes at the center of distant galaxies.
“With this study of pulsars we are trying to look like a spider still in the fabric,” he explained in a press release Stephen Taylor , a researcher at Vanderbilt University (Usa) and co-author of the work. “A good understanding of the barycenter of the solar system, will allow us to detect even the smallest prickle on the network ,” he added. In this case, the shudder of the “spider web” will not occur by the capture of a flying insect, but by the subtle echo of gravitational waves from a supermassive black hole.
The center of gravity of the solar system has been calculated before by means of transmitters and estimations of the positions and trajectories of the planets. However, capturing the gravitational waves of black holes requires a higher precision.
“The problem is that errors in the masses and the orbits would result in distortions in the data of the pulsars that might seem like gravitational waves,” explained Joe Simon, co-author of the study and researcher at the Jet Propulsion Laboratory (JPL) in Pasadena, California.
This implies that the efforts of Taylor and his team, to look for changes in the rhythms marked by the pulsars in the data of the experiment NANOGrav could fall on deaf ears. But you might have luck.
“Our precise observation of pulsars, scattered across the galaxy, we have been located in the cosmos better than we had been able to achieve until now ,” said Stephen Taylor.
In fact, the authors have located the position of the center of the solar system with a precision of 100 meters . To get an idea of what this means, if the Sun were the size of a soccer ball the authors would have located the center with a margin that is comparable to the thickness of a hair.
Where is that center? The influence of Jupiter and Saturn, which unite 90% of the mass of all the planets, moves from the center of the Sun to its surface.
Taylor believes that, if you finally manage to observe the gravitational waves from supermassive black holes, you could “gain a more holistic view of all kinds of black holes in the universe”. This, in turn, is interesate to study galaxy evolution and test general Relativity and other theories.