Science a GoGo's Home Page Forums General Discussion Physics Forum Sunlight alters asteroids' spin

Sunlight can cause asteroids to spin more quickly, scientists said Wednesday, showing anew just how dynamic a place our solar system can be. International teams of scientists studying two asteroids, one about a mile wide and the other about 375 feet wide, confirmed a previously unproven theory that sunlight can affect the rotation of asteroids because they tend to be irregularly shaped and not perfectly round. Stephen Lowry of Queen's University Belfast in Northern Ireland said the findings boost the understanding of the physical properties and dynamics of asteroids -- hunks of metal and rock rattling around in space. "This is important as asteroids are leftovers from the formation of the solar system, along with comets, and so by studying them we gain insights into what the solar system was like some 4.5 billion years ago," Lowry said by e-mail. In research appearing in the journals Nature and Science, the scientists focused on the so-called YORP effect, named for four scientists who inspired the theory. The idea is the sun's heat serves as a propulsion engine on the irregular features of an asteroid's surface. "YORP can accelerate or decelerate the rotation rate," Mikko Kaasalainen of the University of Helsinki in Finland said by e-mail. When sunlight hits the asteroid, the solar energy is absorbed and then radiated back into space. When the asteroid is not spherical, this can create a push off parts of its surface that alters its spin. "Depending on the exact shape, the effect on the entire asteroid's surface can lead to a net torque, which can slowly alter the time it takes the asteroid to make one full revolution," Lowry said. For the full article Click Here .

This is sort of off topic but I was reading about the makeup of asteroids today in the paper, and was surprised to hear they can be very varied in their composition and can be a lot bigger that I had thought! Some are rock, some are ice particles and others can be a conglomeration of rubble, which I did not know as I thought they were all composed of rock (unlike comets ). The article discussed ways of diverting asteroids that were expected to pass too close or collide with earth, and concluded that it is a lot more tricky than earlier thought because of their variable composition. This post seems to challenge the paper's suggested best method of diverting rocky asteroids, ie the use of small explosives to change the path of the asteroid to pass close by, but avoiding collision with earth. If it already has it's own 'drive' would that not complicate things? Is it possible to divert a determined asteroid anyway?

The last sentence of the article suggested that, although passes near earth do occur, at the moment Climate Change seemed to have a more immediate chance of causing catastrophe!

One day I'll learn how to post links to articles like this!

Ellis,
Posting a link is quite easy. Just go to the address bar, copy the URL, and click on the reply window on SAGG. Then paste the URL into the window, and the BB software does the rest.

Happy posting! :-)

Amaranth

Thanks Amaranth- one day I will 'bravely go' where I have never been before!

Ellis - the biggest trick in diverting an asteroid is in detecting it early enough. It is very likely that the first warning we will have of a massive asteroid hit will be the shock wave as it hits our upper atmosphere a second or two before it hits the Earth.

If we detect it a few weeks beforehand, then we'll basically have mass world-wide panic as people try to find places underground to hide. There will be a surge in bomb-shelter building, and lots of looting. And they'll do the only thing they possibly can - try to get a nuclear weapon up there as soon as possible and try to divert it while fingers are crossed hoping that they don't just turn a big rock into lots of smaller radioactive rocks.

If we have a few months, we'll have more of an opportunity to study it and try to figure out the best places to set off explosions in such a way that even though it'll still probably turn it into lot of radioactive rocks, most of those rocks will stand a good chance of missing us us.

If we have a few years, then we'll probably be fine. At that point, we might still use the explosive solution. Or, we might land something on the asteroid with propulsion systems to move it. We wouldn't need to move it far - just a tiny, insistent nudge over time.

If we have a decade or two, then we won't really be terribly sure that it's really going to hit us in the first place, but as the likelihood increases, there will be lots of worldwide government spending on finding the best solution and we'll almost certainly be fine.

But, pessimistic as it is, my bet is still on the 1-2 second warning. (Which is why we need more funding for NEO scanning.)

w