Every day, about 100 tons of dust and particles the size of a grain of sand hit the Earth. But once a year, an asteroid the size of a car crashes into our planet. In 2013, one of them exploded about 30 kilometers above the Russian city of Chelyabinsk. The energy released was about 500 kilotons, thirty times more than that of the Hiroshima nuclear bomb.
To avoid similar impacts, especially in densely populated areas, a team led by Amy Mainzer have resorted to a simple but ingenious way to detect these small near-Earth objects (NEO). The system will be presented in an article at the April meeting of the American Physical Society. The new recognition method will help in efforts to prevent future impacts on Earth.
“If we detect an object just a few days before the impact,” Mainzer explains, “our options are greatly limited, so we have focused on finding NEOs when they are farther from Earth, which gives us more reaction time. NEOs are intrinsically weak because they are mostly really small and far from us in space, the problem is that some of them are as dark as ink and trying to detect them against the black of space is very complicated.”
The new technique involves, instead of using visible light to detect NEOs, resorting to one of its characteristics: heat. Asteroids and comets raise their temperature due to the sun and, therefore, glow brightly in thermal (infrared) wavelengths, which makes them easier to detect with telescopes such as NEOWISE.
“With the NEOWISE mission,” Mainzer adds, “we can detect objects regardless of the color of their surface and use them to measure their sizes and other surface properties.”
Knowing the surface properties of NEOs gives experts an idea of their size and composition, both critical details when developing a defensive strategy. One possibility is to “push” an asteroid to divert it from its trajectory, in order to calculate the necessary energy it is essential to know how big it is and what it is made of. This knowledge will also help to understand how the solar system formed.
“These objects are intrinsically interesting because some are believed to be as old as the original material that formed the solar system,” Mainzer concludes. “And one of the findings we have found is that NEOs have a very diverse composition.”
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