For 20 years a specific software of NASA calculated the risk of the impact of asteroids. Now there is a new edition with Sentry-II.
The American space agency NASA has been searching the near-Earth solar system with the software Sentry since 2002 for potentially dangerous asteroids that could eventually hit the earth. According to the authority, around 3,000 new near-earth asteroids, NEA for short, are discovered every year. We now know around 28,000 of these NEAs.
"In order to better assess the probability of NEA impacts," the software's algorithm has been improved and Sentry-II has been developed. One of the reasons for this was the new generation of more advanced telescopes for surveying space. The agency suspects that the newly discovered NEAs will increase rapidly in the next few years.
When asked by the House of Astronomy in Heidelberg, the astronomer Carolin Liefke told Golem.de that the Vera Rubin telescope will be one of these advanced telescopes: "As for the number of objects that are simply discovered on the side: That will increase significantly. There will be a lot in store for us. From a flood of newly discovered asteroids and comets to other things. " The telescope is expected to go into operation in October 2023.
Better Software, Faster Calculation
In order to estimate the risk of impact on Earth, the orbits of every known near-Earth asteroid are precisely calculated. This happens at the Center for Near-Earth Object Studies (CNEOS), which is part of NASA's Jet Propulsion Laboratory. According to the development manager of Sentry-II, Javier Roa Vicens, the new software can " reliably determine the impact probability of a newly discovered asteroid in the next 100 years" in less than an hour.
In addition, special cases that were not recorded by the original sentry can also be taken into account. Sentry-II then reports the objects in the CNEOS Sentry table, in which one can see which asteroids are coming close to the earth and how high their impact risk is.
But even after that, the orbit of the asteroids must continue to be observed and calculated. In addition to the sun, there are other celestial bodies with a large gravitational force in our solar system. These could deflect the orbit of the asteroids.
The Faulty Special Cases of The Old Software
According to NASA, the software can take this factor into account and thus calculate where the asteroid will be in the future. However, it has not yet been possible to take into account the non-gravitational forces, such as, for example, non-thermal forces that are caused by the heat of the sun.
In the case of a rotating asteroid, the side facing the sun is heated, while the side facing away remains cold. As soon as the heated side reaches the night side of the asteroid, it cools down and infrared energy is released. This exerts a tiny but continuous thrust on the asteroid for a brief moment - which changes the orbital movement of an asteroid for decades and centuries.
Another problem was misprediction when the asteroids were easily diverted by the gravitational pull of Earth and other planets. The old software then predicted a dramatically increased risk of impact. "The special cases that we find are numerically only a tiny fraction of all NEAs for which we calculate impact probabilities," says Roa Vicens. With Sentry-II these errors are supposed to have been corrected, as the new algorithm models thousands of random points in the entire uncertainty region in order to precisely record possible impact risks.