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Under certain circumstances, the sun can heat an asteroid unevenly, causing the space rock to radiate heat energy asymmetrically. The result can be a small pressure in a particular direction, an effect called Yarkovsky acceleration that can change the path of one Asteroid through space.
Since astronomers had not previously measured this solar rhythm on Apophis, they did not take it into account when calculating the threat that asteroid 2068 poses to us. Those previous calculations showed a small chance of impact – about 1 in 150,000.Connected: Potentially dangerous asteroids (images)
A new study now shows that the asteroid deviates about 170 meters from its previously predicted orbit every year due to the Yarkovsky effect, University of Hawaii lead author and astronomer David Tholen said at a news conference on Oct. 26. .
“Basically, the heat emitted from an asteroid gives it a little boost,” he explained during a virtual meeting of the American Astronomical Society’s division of planetary sciences. You will find the file Press conference on YouTube here. Start at the 22 minute mark.
“The hottest hemisphere [of the asteroid] it would press a little harder than the colder hemisphere, and that would cause the asteroid to deviate from what a pure gravitational orbit would predict, ”Tholen said.
It showed the orbit of Apophis at 340m wide and said that astronomers believed they had enough observations of the asteroid, collected in the years following its discovery in 2004, to more or less rule out an impact in 2068. However, these calculations were based on an orbit that was not affected by solar energy. Ultimately, this means that we can’t yet rule out that Apophis will pose 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, by 2029, the asteroid will get very close (but at the same time safe) to our planet, allowing ground-based telescopes – including the powerful Arecibo Observatory radar – to take a more detailed look at the surface and shape of the planet. ‘asteroid. Apophis will be so close that it will be visible to the naked eye in the third order of magnitude – about as bright as that Doppelstern Cor Caroli.
“Of all the dates, Friday April 13, April 13 [2029]When the overflight happens, “Tholen said.” Obviously, the narrow approach of 2029 is crucial. We will know exactly where it will happen next [Apophis] when it happened to 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 images of the asteroid with very high precision, with an error of only 10 milliseconds for each observation. (A millisecond is one thousandth of an arc second, an angular measure that helps scientists measure cosmic distances.)
“We got the position of this asteroid really very good,” Tholen said. “This was enough to give us strong recognition of the Yarkovsky effectwhat we have been expecting for a long time. ”
Tholen noted that Apophis was problematic for astronomers as “numerous impact scenarios” have been predicted (and then largely excluded) since it was first discovered in 2004. For example: Initially, scientists calculated a 3% chance that Apophis would invade our planet in 2029, a prediction Tholen said was quickly ruled out after further observations showed the true path of the small world.
If there is a risk of impact, astronomers will know how to tackle the problem long before 2068. Engineers around the world are. Develop ideas on how to deflect dangerous asteroids from concepts of our planet ranging from gravitational tugs to “kinetic impactors” that throw an incoming stone off course.
A joint mission between Europe and NASA will also test and observe the deflection of asteroids on a space rock called Didymos from 2022. If all goes as planned, Double Asteroid Diversion Test (DART) from NASA The spaceship will hit “Didymoon”, the moon orbiting Didymos. The European Space Agency will then launch the Hera mission in 2023 or 2024 and arrive in Didymos two years later to see how well the kinetic impactor moved the moon out of its previous orbit.
NASA has a dedicated Planetary Defense Coordination Office This collects observations of asteroids from a network of partner telescopes and crosses scenarios with other US authorities in order to deflect asteroids or (at worst) to evacuate threatened populations from an oncoming space rock. So far, decades of observations have not identified any immediate threats to our planet from asteroids or comets.
Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.
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