Asteroids Fizzle Out When Approaching The Sun

February 19, 2016 | by Alfredo Carpineti

Photo credit: Asteroid Ida. NASA/JPL

Asteroid impacts are a real and present danger to Earth and our survival, but just how much? To find out, an international team of researchers set out to construct a state-of-the-art model of all near-Earth objects (NEOs) in the Solar System, and they discovered that they are being destroyed further from the Sun than previously thought – although still pretty close.

Asteroids are mostly found between the orbits of Mars and Jupiter, but thermal effects can move them into different orbits. Interactions with planets can send these objects towards the Sun and into orbits where they become a potential threat to us.

To keep an eye on this asteroid menace, scientists have developed systems to detect, track and characterize NEOs, with more than 90 percent of objects with a diameter larger than 1 kilometer (0.6 miles) already discovered. According to these models, though, a large number of objects end up hitting the Sun.

Researchers of this recent study used the latest data to construct an improvement on current computer models, to get a better idea of what is going on. But when the model started coming together, they realized there was an issue. The model predicted 10 times more objects than observational data indicated for NEOs within 10 solar diameters (14 million kilometers, 9 million miles).

To account for this, lead author Dr. Mikael Granvik hypothesized that these objects are being destroyed before they have a chance to impact the Sun. “When we take into account that these objects might be disrupting further out to the Sun than was previously thought, then the model started working exactly as it should."

The study, published in Nature, confirms that the Sun is indeed responsible for the destructions, but that most of the objects are broken down by the intense heat beyond a distance of 10 solar diameters, further than thought before. Previously, researchers thought asteroids were only destroyed by hitting the Sun or at least the corona, which is 1 million kilometers from the surface.

The study also highlighted that not all NEOs are the same. Asteroids can be classified as bright or dark, depending on how well they reflect light. A large portion of the asteroids that we can see closer to Earth are typically brighter, although there’s no reason why a brighter asteroid should come closer to us. And according to the new model, darker asteroids are more likely to be destroyed when approaching the Sun, although the reason why is not yet clear.

“You’d think naively that a dark object would get heated up more than a bright one, as a bright one might deflect more thermal radiation. But the effect amounts to only a couple of percents in terms of temperature,” Granvik concluded. “This is telling us something about the composition and possibly the internal structures of the darker objects.”

Studies like this allow us to better understand asteroids and hopefully prevent these objects from becoming an unstoppable danger.