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 used a simple but ingenious way to detect these small objects near the Earth (NEO by its acronym in English). 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 the NEOs when they are further away from Earth, which gives us a longer reaction time. The NEOs are intrinsically weak because they are mostly really small and far away 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 implies, instead of using visible light to detect NEOs, to resort to one of its characteristics: heat. Asteroids and comets raise their temperature due to the sun and, therefore, they shine intensely in the thermal wavelengths (infrared), 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 path, dog to calculate the necessary energy 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 was formed.
"These objects are intrinsically interesting because it is believed that some are as old as the original material that made up the solar system - concludes Mainzer - and one of the findings we have found is that NEOs have a very diverse composition."