PhD meteor specialist, Helena Bates, spoke to the Natural History Museum about the “hazardous” asteroids in Earth’s orbit as NASA’s OSIRIS-REx mission attempts to understand the dangers of space rocks. She explained: “Most of the asteroids in our solar system are left over rocky bodies from the beginning of our solar system. Most of them are between the orbits of Mars and Jupiter but there are a number of them near, what we call, ‘Near Earth Space’.”

She said: “You would think that predicting the orbit of an asteroid would be quite easy, and in principle it is.

“But the problem with very small bodies are that they’re affected by things that we didn’t initially assume that they would be affected by.

“And one is the effect of the Sun, which is called the Yarkovsky effect.”

This effect was discovered by Polish civil engineer, Ivan Osipovich Yarkovsky, in 1900.

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Ms Bates continued: “The Yarkovsky effect is basically when the Sun heats up one side of the rotating body so the asteroid is rotating as it orbits the Sun.

“And as one side heats up, it kind of absorbs heat and then, as it rotates, that side will begin to face away from the Sun and will radiate that heat outwards.

“That basically acts like a small thruster to push the asteroid into a slightly different orbit.

“And because the amount of heat that the asteroid absorbs is to do with things like composition, what the asteroids made of, which we don’t know, that means it’s really really hard to predict the effect of the Sun.”

“So we’re looking into it and scientists are very interested in the effect of this.

“It’s actually one of the focuses of NASA’s OSIRIS-REx mission, which is a sample return mission.”

The US space agency’s main goal for the mission is to obtain a sample of a near-Earth asteroid, and return the sample for a detailed analysis. It was launched in September 2016.

Ms Bates said: “This mission’s currently in orbit around one of these potentially hazardous asteroids and it’s investigating the effect of the Yarkovsky effect on this asteroid’s orbit.

“So hopefully we should get a better handle on how the Sun heating up one side of the asteroid affects the orbits.”



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