Six nights of observations with two powerful telescopes have confirmed that the orbit of the binary asteroid Didymos is perfectly aligned for NASA’s asteroid-crushing DART spacecraft to arrive in late September.
Observations made in early July by the Lowell Discovery Telescope in Arizona and the Magellan Telescope in Chile confirmed earlier orbit calculations from 2021. crash into a smaller rock dubbed Dimorphos to test a potential technique for deflecting an asteroid threatening Earth, which Didymos and Dimorphos do not.
“Measurements taken by the team in early 2021 were critical to making sure DART arrived at the right place at the right time for its kinetic impact on Dimorphos,” Andy Rivkin, co-lead of the DART research team at Johns University of Applied Physics Hopkins. A laboratory in Maryland, the report said. “Confirmation of these measurements with new observations shows us that we do not need any course changes, and we are already on target.”
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Didymos and its moon Dimorphos will make their closest approach to Earth in several years at the end of September, passing at a distance of about 6.7 million miles (10.8 million kilometers) from the planet. At this time, on September 26, the DART spacecraft will crash into the 560 feet (170 meters) wide Dimorphos in an attempt to change its orbit around the 0.5 miles (780 meters) wide Didymos. The experiment, the first ever attempt to alter an asteroid’s orbit, could pave the way for a future planetary defense mission should the asteroid ever threaten Earth.
Scientists need the detailed orbital parameters of the two space rocks for more than just steering DART reliably toward a target. After the impact, astronomers around the world will measure the asteroids’ orbits again to see how Dimorphos’ orbit accelerated after the impact. The change can be quite small and therefore extremely precise measurements of the original configuration are required.
“The before and after nature of this experiment requires a deep knowledge of the asteroid system before we do anything with it,” Nick Moskowitz, an astronomer at the Lowell Observatory in Arizona and one of the leaders of the July observational campaign, said in a statement. . “We don’t want to say at the last minute, ‘Oh, here’s something we haven’t thought of, or phenomena we haven’t considered.’ We want to make sure that any change we see is entirely related to what DART has done.”
In addition to obvious forces, such as the gravitational pull of larger bodies, the orbits of asteroids can be affected by more subtle phenomena, such as solar radiation pressure, the scientists said in a statement.
Dimorphos’ orbit around Didyma is expected to shorten by several minutes after the impact as the Moon approaches the larger asteroid. By measuring the change with the utmost precision, astronomers will be able to gather important information about the structure of Dimorphos and the properties of the material from which it is made.
A recent measurement campaign determined the orbital period of Dimorphos around Didyma by observing the change in brightness that occurs when one asteroid passes in front of another. However, it has been difficult to make enough observations because sky-viewing conditions at this time of year are not favorable due to the short summer nights that coincide with Arizona’s rainy season, the researchers said. Earlier this year, the asteroids were too far from Earth to be observed.
“It was a difficult time of year for these kinds of observations,” Moskowitz said. “We requested six midnight observations, expecting about half of them to be lost due to weather conditions, but we only lost one night. We are very lucky. Now we really have high confidence that the asteroid system is well understood and we are set to understand what happens after the impact.”
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