Under certain circumstances, the sun can heat an asteroid unevenly, causing the space rock to radiate thermal energy asymmetrically. The result can be tiny 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 pace on Apophis, they did not take it into account when calculating the threat asteroid 2068 poses to us. Those earlier calculations showed a tiny chance of impact – around 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 annually due to the Yarkovsky effect, University of Hawaii lead author and astronomer David Tholen said during a news conference on October 26.
“Basically, the heat an asteroid gives off gives it a tiny boost,” he explained during a virtual meeting of the American Astronomical Society’s planetary science division. You will find the Press conference on YouTube here. It starts at the 22-minute mark.
“The warmer hemisphere [of the asteroid] would press a little more than the cooler hemisphere, and that causes the asteroid to deviate from what a pure gravitational orbit would predict, “Tholen said.
It showed the orbit of the 340 m wide Apophis and stated that astronomers believed 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. However, these calculations were based on an orbit that was not affected by solar energy. Ultimately, this means that we cannot 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 track this asteroid very carefully.”
Fortunately, in 2029, the asteroid will come in close (yet safe) proximity to our planet, allowing ground-based telescopes – including the Arecibo Observatory’s powerful radar dish – to take a more detailed look at the asteroid’s surface and shape. Apophis will be so close that it is visible to the naked eye on the third order of magnitude – about as bright as that Doppelstern Cor Caroli.
“Of all dates, Friday April 13th, April 13th When the flyby takes place, “Tholen said.” Obviously, the narrow approach of 2029 is crucial. We’ll know exactly where it happens after that [Apophis] when it happened to Earth, and that will make it a lot 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 a thousandth of an arc second, an angle measurement that helps scientists measure cosmic distances.)
“We got the position of this asteroid really very good,” said Tholen. “That was enough to give us strong recognition of the Yarkovsky effectwhat we’ve been expecting for some time. ”
Tholen noted that Apophis was problematic for astronomers as “numerous impact scenarios” have been predicted (and then largely ruled out) since it was first found 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 address the problem long before 2068. Engineers all over the world are Develop ideas on how dangerous asteroids can be deflected from our planet concepts ranging from gravitational tugs to “kinetic impactors” that would 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 everything works as planned, NASA’s Double Asteroid Diversion Test (DART) 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 at Didymos two years later to see how well the kinetic impactor moved the moon out of its previous orbit.
NASA has a dedicated Coordination Office for Planetary Defense This collects asteroid observations from a network of partner telescopes and runs through scenarios with other US authorities in order to divert asteroids or (in the worst case) to evacuate threatened populations from an incoming 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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