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Astronomers say they will have to keep an eye on the asteroid near the Earth Apophis to see the danger that space rock represents to our planet during a close pass 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 space rock to radiate heat energy away asymmetrically. The result can be a small push in a certain direction, an effect called Yarkovsky acceleration, which can change the path of a asteroid through space.
Since astronomers had never measured this solar push on Apophis before, they did not take it into account when calculating the threat the asteroid poses to us in 2068. Those previous calculations showed a small probability of impact – about 1 in 150,000.
Related: Potentially dangerous asteroids (images)
Now, a new study shows that the asteroid is receding from its previously predicted orbit by around 170 meters per year due to the Yarkovsky effect, astronomer David Tholen of the University of Hawaii at Manoa said during a news conference. of October 26.
“Basically, the heat that an asteroid radiates gives it a very small boost,” he explained during a virtual meeting of the American Astronomical Society’s Division for Planetary Sciences. You can find the file press conference on YouTube here. Start at the 22 minute mark.
“The hottest hemisphere [of the asteroid] it would push slightly more than the colder hemisphere, and this causes the asteroid to move away from what a purely gravitational orbit could predict, ”Tholen said.
By showing the orbit for the 1,120-foot (340 m) wide Apophis, it indicated that astronomers thought they had enough observations of the asteroid – collected in the years after its discovery in 2004 – to more or less rule out an impact in 2068. Those calculations, however, were based on an orbit not affected by the sun’s energy. Ultimately, this means we still can’t rule out Apophis as 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 Arecibo Observatory radar dish – to get a more detailed look at the asteroid’s surface and shape. . Apophis will be so close that it will be visible to the naked eye in third magnitude – about as bright as the binary star Cor Caroli.
“Among all the dates, Friday 13 April, 13 April [2029], that’s when the overflight will happen, “Tholen said.” Obviously, the close approach of 2029 is crucial. We will know later that exactly where it is [Apophis] it was how it crossed the Earth, and that will make it much easier for us to predict future impact scenarios. “
Tholen’s team made the discovery after four nights of observation in January and March with the Subaru Telescope, a Japanese optical-infrared telescope on the summit of Maunakea, Hawaii. The researchers collected 18 exposures of the asteroid with very high accuracy, with an error of only 10 milliarcseconds in each observation. (A milliarcsecond is one thousandth of an arc second, an angular measure that helps scientists measure cosmic distances.)
“We really got the position of this asteroid extremely well,” Tholen said. “This was enough to give us strong detection of the Yarkovsky effect, which is something we’ve been expecting to see for a while now. “
Tholen noted that Apophis has been troublesome to astronomers, with “numerous impact scenarios” expected (and then largely excluded) since it was first discovered in 2004. For example: Initially, scientists calculated a 3% chance that Apophis will crash into our planet in 2029, a prediction Tholen said was quickly ruled out after further observations showed the small world’s true path.
If there is a threat of impact, astronomers will know long before 2068 how to deal with the problem. Engineers all over the world are develop ideas on how to deflect dangerous asteroids from our planet, concepts ranging from gravitational tugs to “kinetic impactors” that would make an oncoming rock off course.
A joint European-NASA mission will also test and observe the deflection of an asteroid in a space rock called Didymos, starting in 2022. If all goes according to plan, Double Asteroid Redirection Test (DART) from NASA the spacecraft 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 well the kinetic impactor did in moving the moon from its previous orbit.
NASA has a dedicated Planetary Defense Coordination Office which collects observations of asteroids from a network of partner telescopes and spans scenarios with other US agencies for asteroid deflection or (at worst) evacuation of threatened populations from an oncoming space rock. So far, decades of observations have found no imminent asteroid or comet threat to our planet.
Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.
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