"The new orbit for the half-kilometer (a third miles) in diameter 1999 RQ36 is the never obtained more precise asteroid orbit," said team member OSIRIS-REx Steven Chesley of NASA Jet Propulsion Laboratory, Pasadena, California. He presented the findings may 19 meeting 2012 asteroids, comets and meteors in Niigata to the Japan.
As Michael Nolan at the Observatory of Arecibo to Puerto Rico in September 2011, accompanied by Arecibo and Goldstone in 1999 and 2005 radar observations, when 1999 RQ36 spent a lot closer to the Earth, showed that the asteroid has deviated from its orbit of gravity by about 100 miles or 160 kilometres, over the past 12 years, a deviation caused by the Yarkovsky effect.
The Yarkovsky effect is the name of the engineer of Russia of the 19th century, who first proposed the idea that a small rocky space object would have, over long periods of time, be significantly encouraged in its orbit by the slight thrust created when it absorbs the sunlight and re-emits while the energy as heat.
"Yarkovsky 1999 RQ36 force at its peak, when the asteroid is closer to the Sun, is only on a half ounce - the weight of three grapes on Earth." During this time, the mass of the asteroid is estimated at about 68 million tonnes. You need extremely precise measurements on long enough to see something so low on something so huge. »
Nolan and his team measured the distance between the Observatory of Arecibo and 1999 RQ36 to an accuracy of 300 metres, or about one-fifth of a mile, where the asteroid was 30 million miles, or 20 million kilometres, of the Earth.
"Who is like measuring the distance between New York and Los Angeles with a precision of two inches and enough to be the size of the asteroid and the Observatory of Arecibo into account in the measurements of fine," said Nolan.
Chesley and his colleagues used the new measures of Arecibo to calculate a series of 1999 RQ36 approaches more close to the Earth as 7.5 million kilometres (4.6 million) of the years 1654 to 2135. He revealed in 11 meetings.
Combining radar results from the Arecibo Observatory with infrared results by the scientists NASA Spitzer Space Telescope have also learned the asteroid 1999 RQ36 that is very light, has the same density as water, autour Chesley reported.
"This study is an important step in understanding the Yarkovsky effect - a subtle force contributing to the orbital evolution of near-Earth objects," said Dante Lauretta, principal investigator for the mission and Professor of planetary science at the University of Arizona.
Lauretta added that "this information is essential to assess the probability of our target asteroid impact and provides important constraints on the mass and density,." allowing us to significantly improve our mission design
The OSIRIS-REx probe is to launch in 2016, reach the asteroid (101955) 1999 RQ36 in 2019, examine closely during an appointment 505 days, then return at least 60 grams (~1.9 ounces) of this land by 2023.
"In addition to exciting Yarkovsky results, low density shows that 1999 RQ36 is likely a loose aggregate of rocks - a pile of rubble called," said Jason Dworkin, the scientific mission of the project and head of astrochemistry at the NASA Goddard Space Flight Center in Greenbelt, MD. "It is therefore an ideal target for OSIRIS-REx to collect loose surface materials."
