NASA researchers have narrowed the orbit of the near-Earth asteroid Bennu — and with it the risk of an upcoming collision. Accordingly, close flyby in 2135 could decide whether the 500-meter segment hits a later runway or not.
If it flew through the “keyhole” in the year 2135, it could hit Earth in September 2182. However, the probability of this is only 1 in 2700.
Its height is about 500 meters and about 60 million tons are heavy asteroid benno It belongs to a few celestial bodies close to Earth, It is currently classified as a potential hazard to Earth. Because in its 1.2-year orbit, this segment crosses the Earth’s orbit over and over again. Every few years it gets relatively close to our planet. This is one of the reasons why NASA chose Bennu as a target for the OSIRIS-REx mission, in which the probe accurately maps the asteroid and a sample take its surface.
The year 2135 is a decisive year
Now a team led by David Farnocchia of NASA’s Jet Propulsion Laboratory has evaluated data collected by the space probe over a two-year period and obtained new information about Bennu’s trajectory and impact risks. “The OSIRIS-REx mission has given us an extraordinary opportunity to more accurately predict where Bennu will be when it approaches Earth in more than a century,” said NASA’s Kelly Fast.
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It is known that the asteroid will come closer to Earth in the year 2135 than its orbit around the Moon. There is no danger of collision, but the effect of gravity on the Earth can change its orbit in such a way that it hits our planet in one of its last rounds. Whether this will happen depends on whether Bennu 2135 flies through one of the “key holes” – locations in near-Earth space where Earth’s gravity can guide the piece on a collision course.
Impact risk at 1:1,750
New calculations based on OSIRIS-Rex data now emerge: Benno will almost certainly miss 24 of the 26 “key gaps”. However, Farnocchia and his team cannot completely rule out the effect by the year 2300. According to her, the risk for this is 0.057 percent or 1:1,750. This puts Benno at the top of the Palermo scale, indicating the risk of an impact. Only the asteroid (29075) 1950 DA, which has a size of about one kilometer, has a similar high list, but it cannot become dangerous until 2880.
NASA researchers suggest that September 24, 2182 is the most likely time for an impact to date — if it comes down to it. According to their calculations, the probability of a collision with Earth on this day is 0.037 percent, or 1:2700. The year 2037 could show whether It will stay at this value or whether it will change. Because then Bennu again comes relatively close to Earth and thus its orbit data can be compared again with the help of telescopes.
The Yarkovsky Effect: A block of three grapes
The so-called Yarkovsky effect is one influencing factor that Varnokia and colleagues examined in more detail for this risk assessment. It happens because solar radiation heats up the sides of the asteroid to different degrees. Depending on the rotation of the piece and its speed of flight, it can easily be deflected inward or outward by this radiation pressure. Especially when it comes to the “keyholes” that mark the path, this can be enough to drastically change the risk of an impact. This can include asteroid Apophis This is the situation.
For Bennu, the researchers determined the Yarkovsky effect as accurately as possible using data from OSIRIS-Rex. The result: “The effect on Bennu is roughly equivalent to the mass of three grapes,” says co-author Steve Chesley of JPL. “That’s incredibly small, but it matters when it comes to impact risks several decades to centuries into the future.”
Has Osiris-Rex changed Benno’s path?
Another factor that scientists examined was the OSIRIS-REx mission itself, in which the space probe used a gas crater when taking its sample in order to slightly excite the surface of the asteroid. Fortunately, the team was able to give all the obvious: “The force exerted on Bennu in this event was small, even compared to other weak influencing factors,” says Richard Byrne of NASA’s Goddard Space Flight Center. “It didn’t change Benno’s injury risk.” (Icarus, 2021; doi: 10.1016/j.icarus.2021.114594)
This article was written by Nadja Podbregar