It’s still very light • The Register


Bennu, already considered the second most dangerous asteroid in the solar system, has a slightly increased chance of hitting Earth in the centuries to come, NASA said this week.

There is, according to the latest calculations, a one in 2,700 (0.037%) chance that the half-kilometer wide space rock will collide with Earth on September 24, 2182, and one in 1,750 (0.057%) chance. hundred) chance of a strike by 2300 – a tiny bit higher than previous estimates.

The spinning top-shaped space rock is one of the two most dangerous known asteroids in the solar system – dangerous to Earth, that is – the other being 1950 DA, which has about 0.3% of chances of hitting our planet on March 16. , 2880. Astronomers know Bennu much better, however, thanks to NASA’s OSIRIS-REx mission in which a spacecraft orbiting the asteroid for years.

The probe briefly touched the surface to obtain a sample of Bennu’s regolith. The machine returns to Earth, where it should arrive on September 24, 2023. The data already collected by this mission was used to recalculate Bennu’s trajectory and therefore his chances of hitting Earth.

“The OSIRIS-REx data gives us so much more precise information, we can test the limits of our models and calculate Bennu’s future trajectory with a very high degree of certainty up to 2135,” said Davide Farnocchia, of the Center for Near-Earth Object Studies (CNEOS), which is managed by NASA’s Jet Propulsion Laboratory (JPL). “We have never modeled the trajectory of an asteroid with this precision before.”

Farnocchia and his colleagues presented their results in the journal Icarus on Tuesday. The NASA man added that “the probability of impact has increased slightly, but it’s not a significant change.”

OSIRIS-REx has provided scientists with the most accurate data to date on Bennu’s size, shape, mass, spin, chemical composition and orbital motion. There are several factors to consider when trying to make your way through the solar system. The team had to model the gravitational interactions between the asteroid and the Sun, and other planets and their satellites, as well as more than 300 other space rocks, and the pressure of the solar wind.

While researchers have a good idea of ​​the asteroid’s path, it can be pushed by something called the Yarkovsky effect. As Bennu spins, the side of his body facing the sun absorbs the heat and pulls away. The heat is then sent back into space as it cools, releasing infrared energy that generates a small push on the asteroid. The effects are tiny but can adjust Bennu’s movement over sufficiently long periods of time. Measurements of the Yarkovsky effect of the OSIRIS-REx probe have thus made it possible to refine Bennu’s trajectory.

NASA has a good explanation of the Yarkovsky effect and its impact on Bennu traveling through gravitational keyholes in the video below.

Youtube video

“The Yarkovsky effect will act on all asteroids of all sizes, and although it was measured from afar for a small fraction of the asteroid population, OSIRIS-REx gave us the first opportunity to measure it in detail then. that Bennu was traveling around the Sun, ”explained Steve Chesley, co-author of the article and principal investigator at JPL.

“The effect on Bennu is equivalent to the weight of three grapes constantly acting on the asteroid – tiny, yes, but significant in determining the chances of Bennu’s future impact over the decades and centuries to come.”

Additionally, NASA did not significantly alter Bennu’s motion when his probe ejected a puff of nitrogen gas to lift dirt in order to collect it and return it to Earth.

“The force exerted on Bennu’s surface during the Touch-and-Go (TAG) event was tiny even when compared to the effects of other small forces considered,” Rich Burns, OSIRIS-REx mission project manager , who was not directly involved in the research, said. “TAG has not changed the likelihood of Bennu impacting Earth. “®

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