Planet-Hunters Are In Queue
Planet-hunters set for big bounty
Rocky planets, possibly with conditions suitable for life, may be more common than previously thought in our galaxy, a study has found.
New evidence suggests more than half the Sun-like stars in the Milky Way could have similar planetary systems.
There may also be hundreds of undiscovered worlds in outer parts of our Solar System, astronomers believe.
Future studies of such worlds will radically alter our understanding of how planets are formed, they say.
New findings about planets were presented at the American Association for the Advancement of Science (AAAS) in Boston.
Nasa telescope
Michael Meyer, an astronomer from the University of Arizona, said he believed Earth-like planets were probably very common around Sun-like stars.
“Our observations suggest that between 20% and 60% of Sun-like stars have evidence for the formation of rocky planets not unlike the processes we think led to planet Earth,” he said. “That is very exciting.”
Mr Meyer’s team used the US space agency’s Spitzer space telescope to look at groups of stars with masses similar to the Sun.
They detected discs of cosmic dust around stars in some of the youngest groups surveyed.
The dust is believed to be a by-product of rocky debris colliding and merging to form planets.
Nasa’s Kepler mission to search for Earth-sized and smaller planets, due to be launched next year, is expected to reveal more clues about these distant undiscovered worlds.
Frozen worlds
Some astronomers believe there may be hundreds of small rocky bodies in the outer edges of our own Solar System, and perhaps even a handful of frozen Earth-sized worlds.
Speaking at the AAAS meeting, Nasa’s Alan Stern said he thought only the tip of the iceberg had been found in terms of planets within our own Solar System.
More than a thousand objects had already been discovered in the Kuiper belt alone, he said, many rivalling the planet Pluto in size.
“Our old view, that the Solar System had nine planets will be supplanted by a view that there are hundreds if not thousands of planets in our Solar System,” he told BBC News.
He said many of these planets would be icy, some would be rocky, and there might even be objects with the same mass as Earth.
“It could be that there are objects of Earth-mass in the Oort cloud (a band of debris surrounding our planetary system) but they would be frozen at these distances,” Dr Stern added.
“They would look like a frozen Earth.”
Goldilocks zone
Excitement about finding other Earth-like planets is driven by the idea that some might contain life or perhaps, centuries from now, allow human colonies to be set up on them.
The key to this search, said Debra Fischer of San Francisco State University, California, was the “Goldilocks zone”.
This refers to an area of space in which a planet is “just the right distance” from its parent star so that its surface is not-too-hot or not-too-cold to support liquid water.
“To my mind there are two things we have to go after: we have to find the right mass planet and it has to be at the right distance from the star,” she said.
The AAAS meeting concludes on Monday.
via bbc
Planet hunters find ’super-Earth’
Planet hunters have discovered an icy “super-Earth” circling a distant star.
International astronomers suspect it is a bare, icy, rocky world, much colder than the Earth and 13 times its mass.
The planet was spotted last April but details have only just been revealed in a paper submitted to Astrophysical Journal Letters.
The extra-solar planet is one of a mere handful detected using a novel technique called microlensing.
The planet orbits a star about half as big as our Sun, positioned some 9,000 light-years away. At -201C, it is one of the coldest extra-solar planets to be discovered.
Andrew Gould, professor of astronomy at Ohio State University, US, was one of the first people to discover it.
He said the find has two main implications.
“First, this icy ’super-Earth’ dominates the region around its star that in our Solar System is populated by the gas-giant planets, Jupiter and Saturn,” he said.
“We’ve never seen a system like this before because we’ve never had the means to find them.
“And second, these icy ’super-Earths’ are pretty common. Roughly, 35% of all stars have them.”
Brightening effect
Professor Gould is leader of the Microlensing Follow-up Network (MicroFUN) collaboration.
It is one of several international groups looking for Earth-like planets in planetary systems other than our own using the phenomenon called gravitational microlensing.
The technique is an indirect way of obtaining information about large celestial objects that are too dim to see.
When a massive object such as a star crosses the path of a background star, it acts like a powerful lens, gravitationally bending and magnifying the light rays from the more distant star.
The object’s gravity amplifies the starlight, causing it to brighten as the body passes in front of the star.
This can be observed by telescopes on Earth as a brightening and fading effect, as the lens star floats across the face of the background star.
Neptune-mass
Clues to the presence of the planet were first seen last April by a Polish astronomy project led by Professor Andrzej Udalski from Warsaw University.
When Gould and Udalski realised the star was brightening extremely quickly one night, they alerted the duty astronomer at the MDM Observatory in Arizona.
“It was four in the morning,” Gould recalled, “I was very excited and frantic to get someone to observe that star.”
Astronomers in Arizona took more than 1,000 measurements of the event, which, coupled with software models, confirmed the presence of a Neptune-mass planet, 13 times heavier than Earth.
Gould suspects the planet is a bare, icy Earth-like one, a sort of cold “super-Earth”, although he cannot be certain.
“We can’t really tell for sure,” he said. “If we start getting more statistics on this type of planet, we could piece together a better story.”
Extraterrestrial life
Since the 1990s, astronomers have discovered some 170 extra-solar, or exoplanets, a planet which orbits a star other than the Sun.
There is great interest in finding extrasolar planets that are like the Earth, since these could, in theory, have the right conditions for supporting life.
In January, a new planet 5.5 times the mass of the Earth - the smallest yet - became the third exoplanet to be detected by the microlensing technique.
Tim Naylor, professor of astrophysics at Exeter University, UK, said microlensing had great promise for the future.
“It holds out the promise that we will discover many Earth-sized planets with this technique,” he told the BBC News website.
via bbc
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