From the MIT Technology Review article of a new paper from Baoyin, et al called "Capturing Near Earth Objects"...
Most of the discussion about near Earth asteroids focuses on whether they represent a threat to Earth and what to do take if they turn out to be heading our way.
But today, Hexi Baoyin and pals at Tsinghua University in Beijing offer a different take. The question they ask is how to place an asteroid in orbit around the Earth.
Their conclusion is a little surprising. They say it's relatively straightforward to nudge a small asteroid in our direction. They've even discovered a number of candidates nearby that we might want to bring as little closer.
Their inspiration is a phenomenon that astronomers have noticed with Jupiter. Every now and again, the gas giant captures a nearby object, which hangs around for a few years and then wanders off into space.
A good example is the comet Oterma which went into orbit about Jupiter in1936 before heading off into the Solar System two years later.
Could a similar thing happen to Earth, ask Baoyin and co. Having studied the orbits of the 6000 known near Earth objects (NEO), they say the short answer is no. None of them will come close enough for Earth to capture.
However, a few of these objects will come maddeningly close. So near, in fact, that a small nudge would send them into Earth orbit. "When such an NEO approaches Earth, it is possible to change its orbit energy...to make the NEO become a small satellite of the Earth," they say.
A particularly good candidate is a 10-meter object called 2008EA9 which will pass within a million kilometres or so of Earth in 2049. 2008EA9 has a very similar orbital velocity as Earth's. Baoyin and co calculate that it could be fired into Earth orbit by changing its velocity by 410 metres per second. That's tiny.
This nudge should place the asteroid in an orbit at about twice the distance of the Moon. From there it can be studied and mined, they say.
Just like Oterma's, this orbit is likely to be temporary so 2008EA9 will probably wander off into the heavens after a few years.
Capturing Near Earth Objects
Authors: Hexi Baoyin, Yang Chen, Junfeng Li
(Submitted on 24 Aug 2011)
Abstract: Recently, Near Earth Objects (NEOs) have been attracting great attention, and thousands of NEOs have been found to date. This paper examines the NEOs' orbital dynamics using the framework of an accurate solar system model and a Sun-Earth-NEO three-body system when the NEOs are close to Earth to search for NEOs with low-energy orbits. It is possible for such an NEO to be temporarily captured by Earth; its orbit would thereby be changed and it would become an Earth-orbiting object after a small increase in its velocity. From the point of view of the Sun-Earth-NEO restricted three-body system, it is possible for an NEO whose Jacobian constant is slightly lower than C1 and higher than C3 to be temporarily captured by Earth. When such an NEO approaches Earth, it is possible to change its orbit energy to close up the zero velocity surface of the three-body system at point L1 and make the NEO become a small satellite of the Earth. Some such NEOs were found; the best example only required a 410m/s increase in velocity.
Cite as: 1108.4767v1 [astro-ph.IM]
Link: MIT Technology Review Article
Link: Paper (PDF format)
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