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Astronomers say they will have to keep an eye on Near-Earth asteroid Apophis to see how the space rock represents a danger for our planet during a close passage in 2068. But don’t panic: the chances of an impact still seem very low.
Under certain circumstances, the sun can heat an asteroid unevenly, causing the space rock to radiate thermal energy asymmetrically. The result can be a small push in a certain direction – an effect called Yarkovsky acceleration, which can change the trajectory of a asteroid through space.
Since astronomers had never measured this solar thrust on Apophis before, they did not take it into consideration when calculating the threat the asteroid poses to us in 2068. These previous calculations showed a low probability of ‘impact – about 1 in 150,000 people.
Related: Potentially dangerous asteroids (images)
Now, a new study shows the asteroid is moving away from its previously planned orbit by about 170 meters per year due to the Yarkovsky effect, senior author and University of Hawaii at Manoa said. , astronomer David Tholen, at a press conference in October. 26.
“Basically, the heat that an asteroid gives off gives it a very little push,” he explained at a virtual meeting of the American Astronomical Society’s Division of Planetary Sciences. You can find the press conference on YouTube here. It starts at 22 minutes.
“The warmer hemisphere [of the asteroid] would push slightly more than the colder hemisphere, and that causes the asteroid to drift away from what a purely gravitational orbit would predict, ”Tholen said.
Showing the orbit of the 1,120-foot-wide (340m) Apophis, it said astronomers believe they have enough sightings of the asteroid – collected over the years after its discovery in 2004 – for more or less exclude an impact in 2068. These calculations, however, were based on an orbit unaffected by energy from the sun. Ultimately, that means we can’t yet rule out that Apophis is a threat in 2068, Tholen said.
“The 2068 impact scenario is still in play,” Tholen said. “We have to follow this asteroid very carefully.”
Fortunately, the asteroid will make a close (but still safe) approach to our planet in 2029, allowing ground-based telescopes – including the powerful radar antenna at Arecibo Observatory – to gain a more detailed look at the surface and the shape of the asteroid. Apophis will be so close that it will be visible to the naked eye, at the third magnitude – about as bright as the binary star Cor Caroli.
“Of all dates, Friday April 13, April 13 [2029], that’s when the flyby takes place, “said Tholen.” Obviously, the close-up approach to 2029 is critical. We will know after this happens exactly where he [Apophis] was on Earth’s passage, and this will allow us to predict future impact scenarios much more easily. “
The Tholen team made the discovery after four nights of observation in January and March with the Subaru Telescope, a Japanese optical-infrared telescope located atop Maunakea, Hawaii. The researchers collected 18 exposures of the asteroid with very high precision, with an error of only 10 milliarcseconds in each observation. (A milliarcsecond is a thousandth of an arc second, an angular measurement that helps scientists measure cosmic distances.)
“We have defined the position of this asteroid very well,” said Tholen. “It was enough to give us a strong detection of the Yarkovsky effect, which we have been expecting to see for a while. “
Tholen noted that Apophis has been troublesome to astronomers, with “many impact scenarios” predicted (then largely excluded) since its discovery in 2004. For example: Initially, scientists calculated a probability of 3% d ‘Apophis hitting our planet in 2029, a prediction according to Tholen was quickly ruled out after further observations showed the small world’s true path.
If there is a threat of impact, astronomers will know well before 2068 how to approach the problem. Engineers around the world are develop ideas on how to deflect dangerous asteroids of our planet, concepts that range from gravitational tugs to “kinetic impactors” that would derail an incoming rock.
A joint Europe-NASA mission will also test and observe the deviation of an asteroid on a space rock called Didymos, from 2022. If all goes according to plan, NASA Double Asteroid Redirection Test (DART) spaceship will crash into “Didymoon”, the moon orbiting Didymos. The European Space Agency will then launch the Hera mission in 2023 or 2024 and reach Didymos two years later, to see how successfully the kinetic impactor has moved the moon from its previous orbit.
NASA has a Planetary Defense Coordination Office which collects asteroid observations from a network of partner telescopes, and which runs scenarios with other US agencies for the deflection of asteroids or (in the worst case) for the evacuation of populations threatened by ‘an incoming space rock. So far, decades of observations have found no imminent threat from asteroids or comets to our planet.
Follow Elizabeth Howell on Twitter @howellspace. follow us on Twitter @Spacedotcom and on Facebook.
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