He compares it to our solar system, which is no longer predictable with confidence after 12 million years. That is astonishingly short," says astronomer Simon Portegies Zwart (Leiden University, the Netherlands). "Already after 462 years, we cannot predict the orbits with confidence. These changes grow exponentially and, in the long run, make the star orbits unpredictable. This means that small perturbations caused by the underlying interactions change the orbits of the stars. Although the stars remain in their orbits around the black hole, the interactions between the stars show that the orbits are chaotic. The simulations of the 27 massive stars and the black hole resulted in a surprise. Now the researchers have expanded their program to deal with 27 stars that, by astronomical standards, move close to the black hole at the center of the Milky Way. With this, they were able to calculate the motions of three imaginary stars. It was only in 2018 that Leiden researchers developed a computer program in which rounding errors no longer play a role in the calculations. For centuries, for example, it was impossible to predict the motions of more than two interacting stars, planets, rocks, or other objects. Simulating 27 stars and their interactions with each other and with the black hole is easier said than done. The researchers have published their findings in two papers in the International Journal of Modern Physics D and in the Monthly Notices of the Royal Astronomical Society. This finding emerges from simulations by three astronomers based in the Netherlands and the United Kingdom. The orbits of 27 stars orbiting closely around the black hole at the center of our Milky Way are so chaotic that researchers cannot predict with confidence where they will be in about 462 years.
The yellow orbit, for example, fluctuates in those 10,000 years in a range of forty times the distance from Earth to sun. It reveals that the stars have considerable variations along their orbits. The right panel is a zoom-in near the crowded center. It seems that the stars do not diverge from their orbits. These orbits have been calculated for 10,000 years. On the left are shown the orbits of the stars. Simulation of the motions of stars around the black hole at the center of the Milky Way.
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