Milky Way teeming with 'billions' of planets 01/12/2012 The Milky Way is home to far more planets than previously thought, boosting the odds that at least one of them may harbour life, according to a study released. Not long ago, astronomers counted the number of "exoplanets" detected outside our own solar system in the teens, then in the hundreds. Today the tally stands at just over 700. But the new study, published in Nature, provides evidence that there are more planets than stars in our own stellar neighbourhood. "We used to think that Earth might be unique in our galaxy," said Daniel Kubas, a professor at the Institute of Astrophysics in Paris, and co-leader of the study. "Now it seems that there are literally billions of planets with masses similar to Earth orbiting stars in the Milky Way." Two methods have dominated the hunt over the past two decades for exoplanets too distant and feint to perceive directly. One measures the effect of a planet's gravitational pull on its host star, while the other detects a slight dimming of the star as the orbiting planet passes in front of it. Both of these techniques are better at finding planets that are massive in size, close to their stars, or both, leaving large "blind spots". An international team of astronomers led by Kubas and colleague Arnaud Cassan used a different method called gravitational microlensing, which looks at how the combined gravitational fields of a host star and the planet itself act like a lens, magnifying the light of another star in the background. If the star that acts as a lens has a planet, the orbiting sphere will appear to slightly brighten the background star. One advantage of microlensing compared to other methods is that it can detect smaller planets closer in size to our own, and further from their hot-burning stars. The survey picked up on planets between 75 million and 1.5 billion kilometres from their stars -- a range equivalent in the Solar System to Venus at one end and Saturn at the other -- and with masses at least five times greater than Earth. Over six years, the team surveyed millions of stars with a round-the-world network of telescopes located in the southern hemisphere, from Australia to South Africa to Chile. Besides finding three new exoplanets themselves -- no minor feat -- they calculated that there are, on average, 1.6 planets in the Milky Way for every star, Cassan told AFP. Whether this may be true in other galaxies is unknown. "Remarkably, these data show that planets are more common than stars in our galaxy -- they are the rule rather than the exception," Cassan said. "We also found lighter planets ... would be more common than heavier ones." One in six of the stars studied was calculated to host a planet similar in mass to Jupiter, half had planets closer in mass to Neptune, and nearly two-thirds had so-called super-Earths up to 10 times the mass of the rock we call home. Another study published the same day in Nature, meanwhile, showed that planets simultaneously orbiting two stars -- known as circumbinary planet systems -- are also far more common than once supposed. There are probably millions of planets with two suns, concluded the study, led by William Welsh of San Diego State University in California. © Copyright AFP Agence France-Presse GmbH - All rights reserved. This material may not be published, broadcast, rewritten or distributed. All reproduction or redistribution is expressly forbidden without the prior written agreement of AFP.

This Wednesday a 400-metre asteroid that goes by the name of 2005 YU55 will pass between the Earth and the moon in what experts describe a “near miss”.

The size of an aircraft carrier, scientists from space agencies around the world are watching this close encounter as their concerns grow over another much bigger asteroid that’s headed our way.

The biggest threat to Earth now is an asteroid called Apophis. In 2029 it will pass so close to Earth we’ll be able to see it with the naked eye. What worries

astronomers most is Apophis passing through a small corridor in space called a key hole where Earth's gravity would change its orbit sending it on a collision course with us seven years later.

"The chances of a big one hitting the Earth are 100 percent, the key question is time frame," Dr Bruce Betts, from the Planetary Society, tells Sunday Night.

The clearest reminder of that danger is the imminent arrival of 2005 YU55. It will give NASA a rare and close insight that could shed new light on the objects.

"There's no chance of it hitting Earth. It's an excellent opportunity for astronomers to get a good look at the object to generate a shape for this object," Don Yeomans, head of NASA’s JPL Spaceguard program, says.

Information about viewing the object from Australia

Last month Yeomans and his team of asteroid trackers calculated there were nearly 20 thousand near Earth asteroids, some one kilometre in size.

“An impact of a large asteroid has the capability of taking out our civilization and not many worries and threats can make that claim so it is worth some effort," he said.

In the Catalina mountains north of Tuscon Arizona, Catalina Sky Survey's Ed Beshore tracks comets and asteroids for NASA using telescopes in the US and in Australia.

He says it’s “entirely possible” for an asteroid to hit Earth and the worst case scenario is the situation where you could find one a day before it gets here.

“Actually we did that we found an object in 2006 that we discovered and it actually hit the Earth the next day, fortunately it was only three metres in size, the size of a car, so it came in over the Sudan desert."

Dr Tom Jones is a former NASA astronaut, he's urging experts to "learn to talk to each other" to avoid a doomsday asteroid.

"We should have a book on the shelf that tells us procedures for deciding when to deflect an asteroid, how it's going to be done, how much it costs, what kind of space craft has to be built and then the world can then pull that plan off the shelf if it's necessary."

"We can actually put our technology to use and stop a catasptrophe from happening in the future and it’s the only natural catastrophe that we know how to stop."

Betts added: "One way of knocking an asteroid off its orbit and making it miss the Earth would be to slam into it with a hyper-velocity big space craft at tens kilometres a second."