Smallest habitable world around sun-like star found

Astronomers have found the smallest planet ever detected in the habitable zone around a star like the sun.

The new planet was found with the Kepler telescope, which searches for signs that a star's light has dimmed because a planet has passed between it and the telescope – an event called a transit.

Kepler-22b is just 2.4 times as wide as Earth(Image: NASA/Ames/JPL-Caltech)

"This discovery supports the growing belief that we live in a universe crowded with life," team member Alan Boss of the Carnegie Institution for Science said in a statement. "Kepler is on the verge of determining the actual abundance of habitable, Earth-like planets in our galaxy."

The planet, named Kepler-22b, lies 600 light years away around a star of the same type (called G) as the sun. It is about 2.4 times as wide as Earth and orbits its star every 290 days, right in the middle of its star's habitable zone, where liquid water can exist on an object's surface.

Transit observations cannot pinpoint its mass, however. Astronomers have used other telescopes to search for signs that the planet's gravitational tugs are causing its host star to wobble, but so far have not detected any wobbles. That means the planet's mass must be less than 36 times that of the Earth.

It is close in size to a class of planets called super-Earths, which are up to about 2 times as wide as Earth. "We have no planet like this in our solar system," says Bill Borucki, Kepler's chief scientist at NASA's Ames Research Center in Moffett Field, California. He announced the find on Monday at the Kepler Science Conference at NASA Ames.

Just right

The allowed mass range means the planet could be rocky and could contain water, Borucki says. Ground-based observations in mid-2012, when the patch of sky where the planet lies is more easily visible, could help astronomers nail down the planet's mass. That will help them identify its composition.

Two previous rocky planet candidates have been found in the habitable zones of their stars, but in both cases the stars were cooler than the sun.

And neither candidate was found right in the middle of its star's "Goldilocks" zone, which could boast the best conditions for hosting life as we know it. Kepler-22b's surface is probably a balmy 22 °C, Borucki said.

Scanning for ET

The Kepler telescope has been staring at more than 150,000 stars between the constellations Cygnus and Lyra for the past 1000 days. The Kepler team has now found more than 2300 candidate exoplanets, about 1000 more than itreported in February. Ten of those span no more than about twice Earth's width.

To confirm a new planet, scientists must observe three of its transits. Mission scientists saw the first transit of Kepler-22b three days after Kepler began collecting data in 2009. The third transit appeared in December 2010. "It's a great gift," Borucki said. "We consider this our Christmas planet."

"It's conceivable that these new planet candidates and their [potential] moons could have life," Borucki said.

The SETI Institute in Mountain View, California, will observe the new candidates with its Allen Telescope Array of radio telescopes in California in the hopes of detecting signals from any extraterrestrial civilisations there, said the institute's Jill Tarter. The array had been offline since April due to budget cuts but restarted observations on Monday after raising funds by partnering with the US air force and crowdsourcing donations.

Source New Scientist

Salty Plumes Point to Underground Ocean inside Saturn's Moon Enceladus

A NASA spacecraft that in 2005 discovered watery plumes spewing from the surface of Saturn's icy moon Enceladus has now found compelling evidence that the plumes stem from an underground reservoir of saltwater.

WATERWORKS: Abundant salt grains in the plumes spewing from Enceladus point to a large underground reservoir in the icy moon.

The Cassini probe in 2008 and 2009 flew through a towering plume emanating from the moon's southern polar region and sampled its contents. In an analysis published online June 22 in Nature, a team of researchers reports that the composition of the plume is most easily explained by a sizable subterranean body of water. (Scientific American is part of Nature Publishing Group.) Cassini's instruments were not designed to make such measurements—and in fact the mission was supposed to have ended before the flyby took place—but with a postponed retirement and a few on-the-fly software tweaks the versatile spacecraft was able to get a whiff of the geyserlike ejecta.

The plumes have since their discovery been known to be rich in water vapor, but their origin has remained unsettled. Even in the absence of a liquid reservoir belowground, water vapor could stem from some of Enceladus's abundant ice sublimating directly to vapor in the vacuum of space or from the breakdown of hydrated solids called clathrates.

But whereas a liquid reservoir in contact with the moon's rocky core should contain dissolved salts that would be injected into an upwelling geyser, sublimating ice or decomposing clathrates would be much less efficient at producing a salty plume. Planetary scientist Frank Postberg of Heidelberg University and the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, and his colleagues gathered some support for the saltwater hypothesis in 2009 when they showed that some particles in Saturn's diffuse E ring were salt-rich. The E ring is fed by Enceladus's plumes, so the implication was that the salty grains originated in the icy moon's hypothesized subterranean ocean and were ejected into the ring as a kind of frozen sea spray.

But with salty grains constituting only a small percentage of the E ring particles, the ocean hypothesis was hardly a lock. In the new analysis of Cassini's dives through the plumes Postberg and his co-authors found a much greater salt concentration—almost all the particles near the source of the plumes are salty ices. It now becomes much more difficult to explain Enceladus's eruption without invoking a large underground reservoir. "Over 99 percent of the emitted ice being salt-rich, that makes a much stronger case [for an ocean], and it's not in agreement with ice sublimation," Postberg says. "Now, with 99 percent, we know that it's just not plausible to be coming from a solid." The salt-rich grains are heavy and tend to fall back to the surface, explaining their relative paucity in Saturn's E ring compared with lighter, salt-free particles.

"They got a sniff of these salty ice grains when they flew through the E ring," says planetary scientist Francis Nimmo of the University of California, Santa Cruz, who did not contribute to the new study. "Now that sniff has become—practically everything is salty. It makes the case that these grains are coming from some liquid reservoir kind of inescapable."

The icy moon, just 500 kilometers in diameter, could be one of several moons in the solar system to harbor underground stores of liquid water. Some evidence has hinted at a subterranean ocean for Titan, a much larger Saturnian moon, as well as for Ganymede, Callisto and Europa, three of Jupiter's largest satellites, and for Neptune's moon Triton.

But just what Enceladus's reservoir would look like is somewhat uncertain. The salt content implies a body of water in contact with the moon's rocky core, which Enceladus's density indicates is dozens of kilometers below the surface, but the escaping vapor at the surface points to evaporation at much shallower subterranean depths. One possibility is a series of near-surface misty caverns fed by a saltwater ocean at Enceladus's core. "You have an ocean at depth at the interface of the ice and the rocky core," Postberg says. "But it must be connected with reservoirs that are only a few hundred meters below the surface."

The scale and complexity of that hypothesized plumbing raises some questions. "These 'deep misty caverns' must be truly immense, and connected in complicated ways with the ocean and with the surface," says Nicholas Schneider, a planetary scientist at the University of Colorado at Boulder. The detection of salt in the plumes is indeed consistent with a liquid source, Schneider says, but geophysicists now need to come up with a viable description of a watery internal structure for the satellite. "After all, we're really using the plumes to tell us what's going on inside, and nobody's taken up that challenge," he says. "We're watching what little Enceladus spits up, but that hardly tells us much about the baby's insides!"

Another question is how a tiny, icy satellite like Enceladus could maintain a large body of liquid water. The tidal energy generated by Enceladus's orbit around Saturn provides some heating, but not enough to keep a large amount of water from freezing over billions of years. "The big question that we still don't have answered is: How can an ocean survive for geological time?" Nimmo says. "Most likely the answer is it's not a global ocean at all but more of a regional sea." In other words, Enceladus's tidal heat could be concentrated on the south polar region, allowing for a localized reservoir of liquid there on an otherwise frozen moon.

Perhaps Cassini, which has been exploring Saturn since 2004, will deliver more answers about the mysterious ice world in the coming years. The spacecraft's mission, originally set to end in 2008, has been extended through 2017.

Source Scientific American

Why the universe wasn't fine-tuned for life

IF THE force of gravity were a few per cent weaker, it would not squeeze and heat the centre of the sun enough to ignite the nuclear reactions that generate the sunlight necessary for life on Earth. But if it were a few per cent stronger, the temperature of the solar core would have been boosted so much the sun would have burned out in less than a billion years - not enough time for the evolution of complex life like us.

In recent years many such examples of how the laws of physics have been "fine-tuned" for us to be here have been reported. Some religious people claim these "cosmic coincidences" are evidence of a grand design by a Supreme Being. In The Fallacy of Fine-tuning, physicist Victor Stenger makes a devastating demolition of such arguments.

A general mistake made in search of fine-tuning, he points out, is to vary just one physical parameter while keeping all the others constant. Yet a "theory of everything" - which alas we do not yet have - is bound to reveal intimate links between physical parameters. A change in one may be compensated by a change in another, says Stenger.

In addition to general mistakes, Stenger deals with specifics. For instance, British astronomer Fred Hoyle discovered that vital heavy elements can be built inside stars only because a carbon-12 nucleus can be made from the fusion of three helium nuclei. For the reaction to proceed, carbon-12 must have an energy level equal to the combined energy of the three helium nuclei, at the typical temperature inside a red giant. This has been touted as an example of fine-tuning. But, as Stenger points out, in 1989, astrophysicist Mario Livio showed that the carbon-12 energy level could actually have been significantly different and still resulted in a universe with the heavy elements needed for life.

The most striking example of fine-tuning appears to be the dark energy - or energy of the vacuum - that is speeding up the expansion of the universe. Calculations show it to be 10¹²⁰ bigger than quantum theory predicts. But Stenger stresses that this prediction is made in the absence of a quantum theory of gravity, when gravity is known to orchestrate the universe.
Even if some parameters turn out to be fine-tuned, Stenger argues this could be explained if ours is just one universe in a "multiverse" - an infinite number of universes, each with different physical parameters. We would then have ended up in the one where the laws of physics are fine-tuned to life because, well, how could we not have? (For a related philosophical discussion read this article.)

Religious people say that, by invoking a multiverse, physicists are going to extraordinary lengths to avoid God. But physicists have to go where the data lead them. And, currently, there are strong hints from string theory, the standard picture of cosmology and fine-tuning itself to suggest that the universe we can see with our biggest telescopes is only a small part of all that is there.

Source New Scientist

Meteorite holds clues to organic chemistry of the early Earth

Washington, DC— Carbonaceous chondrites are a type of organic-rich meteorite that contain samples of the materials that took part in the creation of our planets nearly 4.6 billion years ago, including materials that were likely formed before our Solar System was created and may have been crucial to the formation of life on Earth. The complex suite of organic materials found in carbonaceous chondrites can vary substantially from meteorite to meteorite. New research from Carnegie's Department of Terrestrial Magnetism and Geophysical Laboratory, published June 10 in Science, shows that most of these variations are the result of hydrothermal activity that took place within a few million years of the formation of the Solar System, when the meteorites were still part of larger parent bodies, likely asteroids.

Organic material in carbonaceous chondrites shares many characteristics with organic matter found in other primitive samples, including interplanetary dust particles, comet 81P/Wild-2, and Antarctic micrometeorites. It has been argued by some that this similarity indicates that organic material throughout the Solar System largely originated from a common source, possibly the interstellar medium.
A test of this common-source hypothesis stems from its requirement that the organic diversity within and among meteorites be due primarily to chemical and thermal processing that took place while the meteorites were parts of their parent bodies. In other words, there should be a relationship between the extent of hydrothermal alteration that a meteorite experienced and the chemistry of the organic material it contains.
If--as many have speculated--the organic material in meteorites had a role to play in the origin of life on Earth, the attraction of the common-source hypothesis is that the same organic material would have been delivered to all bodies in the Solar System. If the common source was the interstellar medium, then similar material would also be delivered to any forming planetary system.

The research team—led by Christopher Herd of the University of Alberta, Canada, and including Carnegie's Conel Alexander, Larry Nittler, Frank Gyngard, George Cody, Marilyn Fogel, and Yoko Kebukawa—studied four meteorite specimens from the shower of stones, produced by the breakup of a meteoroid as it entered the atmosphere, that fell on Tagish Lake in northern Canada in January 2000. The samples are considered very pristine, because they fell on a frozen lake, were collected without hand contact within a few days of landing and have remained frozen ever since.

The samples were processed and analyzed on the microscopic level using a variety of sophisticated techniques. Examination of their inorganic components indicated that the specimens had experienced large differences in the extent of hydrothermal alteration, prompting an in-depth examination of their organic material. The team demonstrated that the insoluble organic matter found in the samples has properties that span nearly the entire range found in all carbonaceous chondrites and that those properties correlate with other measures of the extent of parent body alteration. Their finding confirms that the diversity of this material is due to processing of a common precursor material in the asteroidal parent bodies.

The team found large concentrations of monocarboxylic acids, or MCAs, which are essential to biochemistry, in their Tagish Lake samples. They attributed the high level of these acids to the pristine nature of the samples, which have been preserved below zero degrees Celsius since they were recovered. There was variety in the types of MCAs, which they determined could also be due to alterations that took place on the parent bodies.
The samples also contained amino acids—the essential-for-life organic building blocks used to create proteins. The types and abundances of amino acids contained in the samples are consistent with an extraterrestrial origin, and were clearly also influenced, albeit in a complex way, by the alteration histories of their host meteorites.

"Taken together these results indicate that the chemical and thermal processing common to the Tagish Lake meteorites likely occurred when the samples were part of a larger parent body that was created from the same raw materials that formed our Solar System," said Larry Nittler of Carnegie's DTM. "These samples can also provide important clues to the source of organic material, and life, on Earth."

Source  ScienceAlert!

Earth-bound asteroids carried ever-evolving, life-starting organic compounds

Detailed analysis of the most pristine meteorite ever recovered shows that the composition of the organic compounds it carried changed during the early years of the solar system

(Edmonton) Detailed analysis of the most pristine meteorite ever recovered shows that the composition of the organic compounds it carried changed during the early years of the solar system. Those changed organics were preserved through billions of years in outer space before the meteorite crashed to Earth.
The research team, led by University of Alberta geologist Chris Herd, analyzed samples of a meteorite that landed on Tagish Lake in northern British Columbia in 2000. Variations in the geology of the meteorite samples were visible to the naked eye and indicated the asteroid, from which the meteorite samples originated, had gone through substantial changes.

The researchers began looking for variations in the organic chemistry that corresponded with variations in the meteorite's geology. Herd says they found a surprising correlation, which gave researchers a snapshot of the process that altered the composition of organic material carried by the asteroid. Among the organic compounds studied were amino acids and monocarboxylic acids, two chemicals essential to the evolution of the first, simple life forms on Earth.

Herd says the finding shows the importance of asteroids to Earth's history.
"The mix of prebiotic molecules, so essential to jump-starting life, depended on what was happening out there in the asteroid belt," said Herd. "The geology of an asteroid has an influence on what molecules actually make to the surface of Earth."
Herd says that, when the asteroid was created by the accumulation of dust around the infant sun, it contained ice. The ice warmed and turned to water, which began percolating and altering the organic compounds buried in the rock.

The Tagish Lake meteorite is considered to be one-of-a-kind because of its landing and handling. It was January when the meteorite exploded at an altitude of 30 to 50 kilometres above Earth and rained meteorite fragments down on the frozen, snow-covered lake. The individual who recovered the samples consulted with experts beforehand and avoided any contamination issues.
Herd says the meteorite's pristine state enabled the breakthrough research. "The variations in the organic makeup are true to what was happing inside the asteroid," said Herd. "This is exactly what has been orbiting in the asteroid belt for the last 4.5 billion years."

Source EurekaAlert!

Listening out for alien life

Astronomers at the University of California, Berkeley, have this month trained the world's largest steerable radio telescope on 86 Earth-like planets. The data collected by the telescope will later be analsyed by an estimated one million amateur alien hunters, the users of SETI@home, for messages from other civilisations. SETI@home is a distributed computing programme which uses people's home computers in the search for extraterrestrial intelligence.

 The Robert C. Byrd Green Bank Telescope in West Virgina. Image courtesy of NRAO/AUI.

"We've picked out the planets with nice temperatures — between zero and 100 degrees Celsius — because they are a lot more likely to harbour life," says physicist Dan Werthimer, chief scientist for SETI@home and a veteran SETI researcher.

Werthimer's 30-year-old SETI project normally uses the world's largest radio telescope, the Arecibo receiver in Puerto Rico. But the giant "ear" used for this new search will be the Robert C. Byrd Green Bank Telescope in West Viriginia. It can focus on an area of the northern sky that Arecibo cannot view and it can also scan a larger range of wavelengths, including those away from the region traditionally favoured by alien hunters, called the waterhole. This means that even if aliens are not intentionally sending mesages to us, we may be able to listen in on their private communications.

If you listen out for signals from space, what you hear is a lot of noise. The galaxy itself produces noise at the lower end of the electromagnetic spectrum and atmospheric processes emit noise at the higher end. But inbetween these two extremes, there is a relatively quiet region: an intelligent civilisation trying to send messages across the Universe are likely to use this quieter range in their communications.

It just so happens that this quieter region of the spectrum is associated with the two constituents of water, hydrogen (H) and hydroxyl ion (OH). Both of these emit radio waves, the former with a wavelength of 21cm (1420.40 MHz) and the latter with a wavelength of 18cm (1660 MHz). The band from 18cm to 21cm wavelengths lies within the quieter zone of the spectrum. The idea is that water-based life-forms would recognise these important markers on the spectrum and use them in an attempt to communicate with the rest of the cosmos. For this reason the band is called the waterhole — a place for life to meet and chat. "This is an interesting place, perhaps a beacon frequency, to look for signals from extraterrestrial civilisations," says Andrew Siemion, a graduate student from UC Berkeley.

The Arecibo telescope does indeed focus on a range centering on the 21cm line, but Werthimer says that it's worth widening the search. "Searching for ET around the 21 centimeter line works if civilisations are broadcasting intentionally, but what if planets are leaking signals like 'I Love Lucy'? With a new data recorder on the Green Bank telescope, we can scan a 800 MHz range of frequencies simultaneously, which is 300 times the range we can get at Arecibo."

The 86 planets the telescope will investigate were chosen from the 1,235 planetary systems spotted by the Kepler space telescope in our galaxy. After it has targeted each of these systems, the Green Bank telescope will scan the entire viewing field of Kepler for signals from other planets too. "If you extrapolate from the Kepler data, there could be 50 billion planets in the galaxy," says Werthimer. "It's really exciting to be able to look at this first batch of Earth-like planets."

SETI@home users can expect the first Green Bank data to arrive at their computers in about two months and the complete analysis could take up to a year.

by Marianne Freiberger

Sour ce +Plus Magazine

Kepler Spacecraft Shows That Smaller Planets Abound

NASA's planet-hunting satellite is making the case that it's a small-world galaxy, after all.

BOSTON—Score one for the little guys. After years of obscurity in the corners of distant planetary systems smaller exoplanets are finally shuffling into the spotlight.

NASA's Kepler spacecraft, built to seek out planets in orbit around faraway stars, has since 2009 been monitoring a vast field of stars to see what kind of planets might be found there. Earlier this year scientists working on the mission announced that they had confirmed 15 exoplanets in Kepler's field of view and identified an astounding 1,200 or so additional planetary candidates, which are probable planets that await independent validation. Prior to that announcement, only about 500 extrasolar worlds had been discovered since planet searches first began to bear fruit in the 1990s.

The newfound planet Kepler 10 c, just over twice Earth's diameter, is visible in the foreground of this artist's conception; its smaller neighbor Kepler 10 b is a dark speck on the face of the star.

One of the most fascinating aspects of the Kepler discovery was the small sizes of the planetary candidates. For years the list of known extrasolar planets had been dominated by massive worlds comparable to or larger than Jupiter, the biggest planet in our solar system. Such massive worlds are the easiest to find, whereas more diminutive planets, of roughly Earth or Neptune size, are much more difficult to spot. But Kepler was designed to be sensitive to those smaller worlds, even the temperate, rocky worlds that might be habitable—and it has not disappointed. The spacecraft is showing that smaller planets are common—more common, in fact, than their larger brethren. At least that is how things look in the inner regions of planetary systems, where Kepler's data is currently the strongest.

"There are some Jupiters, there are some Saturns," University of California, Berkeley, astronomer Geoff Marcy said here at the semiannual meeting of the American Astronomical Society (AAS). "But there are far more of the smaller and smaller planets going down to about two Earth diameters."

Kepler looks for the subtle but recurrent dimming of a star that often indicates the presence of an orbiting planet passing in front of its parent star and blocking a tiny fraction of its light. Planets that orbit close to their star, and  therefore complete a full orbital revolution quickly, show up more often in Kepler's data. Marcy and his colleagues have focused on planets with orbital periods of 50 days or less because those planets have already revealed themselves to Kepler multiple times. In terms of orbital distances that translates to planets orbiting within about one fourth the distance Earth keeps from the sun.

Marcy and his colleagues have used Kepler's data set to extrapolate how often planets of different sizes appear around stars, taking into account the biases that make Kepler spot some planets, yet miss others. (For every planet that orbits its star in just such a way that it crosses Kepler's line of sight, there might be five to 20 other worlds that are not so favorably aligned.) The team found that planets of just a few times Earth's diameter are quite common around stars of the sun's spectral type. "If you take a sample of G-type, main-sequence stars, 8 percent of them will have two- to 2.8-Earth-radii planets with orbital periods of less than 50 days," Marcy said.

A potentially habitable rocky world would have to orbit somewhat farther from its star, preferably in a temperate Earth-like orbit of 365 days or so. Kepler will need more time to investigate those longer-period planets thoroughly, but the trends are favorable for the existence of small planets in more temperate orbits. Within Kepler's short-period planetary candidates, the number of smaller planets increases as the distance from the star increases. "There are apparently more and more small planets, at least edging out toward 50 days," Marcy said.

As for the existence of many of the even smaller planets, those Earth-size worlds that astronomers have long sought, the jury is still out. "We see a very rapid rise as we go to smaller objects, then a precipitous fall as we go to Earth-size and smaller planets," Kepler principal investigator Bill Borucki of NASA Ames Research Center said at the meeting. "We don't know what that represents." It could be that the small dimming signals produced by such tiny worlds are simply hard to find in the noise of the data. Both Borucki and Marcy cautioned that it was too early to make any inferences on the frequency of Earth-size planets, which are expected to take more time to identify.

Kepler's potential for spotting relatively small worlds was highlighted by the announcement at the AAS meeting of a newfound planet from the mission. Francois Fressin of the Harvard–Smithsonian Center for Astrophysics said that he and his colleagues have vetted a candidate planet, now known as Kepler 10 c, which has a diameter 2.2 times that of Earth. Kepler 10 c resides in a planetary system with the even smaller Kepler 10 b, which was announced in January. At the time of that announcement Kepler 10 c was an intriguing hint that could not be validated. But Fressin and his colleagues used complementary observations from NASA's Spitzer Space Telescope as well as a supercomputer program that simulates confounding astronomical phenomena that might mimic the signal of a planet to conclude that there is only a one in 60,000 chance that Kepler 10 c is not a planet.

Source Scientific American

Free Worlds: Billions of Extra-Stellar Planetary Bodies May Be Adrift in the Galaxy

 When is a planet not a planet? A new study claims that the Milky Way is filled with Jupiter-mass celestial objects that do not orbit any star.

Pluto, please step aside. The beleaguered world has for the past several years been at the center of the debate about what defines a planet. Now a new crop of astronomical objects has arrived to further cloud the matter.

The Pluto issue was formally resolved in 2006, when the International Astronomical Union (IAU) relegated Pluto and its diminutive ilk to dwarf planet status. (The conversation has not stopped, however; among a number of recent Pluto-centric books are titles like  The Case for Pluto and  How I Killed Pluto and Why It Had It Coming.)

A new study finds that numerous planet-mass objects could be wandering freely through the galaxy. Above, an artist's depiction of one such world. Image: NASA/JPL-Caltech/R. Hurt

Outside the solar system the issue is less clear—what distinguishes a star from a brown dwarf, which is a sort of failed star not massive enough to burn hydrogen in fusion reactions? What distinguishes a brown dwarf from a planet? And now, most puzzling of all, what to call an object that seems too small to be anything other than a planet but that floats freely through interstellar space rather than orbits a star? Such objects are numerous in the galaxy, and possibly more numerous than ordinary stars, a new study concludes.

Two astronomical collaborations report in the May 19 Nature that they have located a population of 10 celestial objects, each with about the mass of Jupiter, with no detectable host star. (Scientific American is part of Nature Publishing Group.) By extrapolation, the study's authors, from the Microlensing Observations in Astrophysics (MOA) collaboration and the Optical Gravitational Lensing Experiment (OGLE) collaboration, calculate that there should be almost twice as many such objects in the Milky Way as there are stars. Some of the newfound objects may simply orbit a star at a distance so great that their host star is not apparent, but the researchers estimate that most of them are indeed free-floating.

"This is a pretty remarkable claim," says astronomer Mark McCaughrean of the European Space Agency. And it will no doubt undergo close scrutiny. But if the interpretation proves correct, a future NASA mission could turn up such free-floating bodies in droves. A planned spaceborne observatory called the Wide-Field Infrared Survey Telescope (WFIRST) should be able to discover 1,000 such objects, says study co-author Takahiro Sumi of Osaka University in Japan, a member the MOA group.

Other researchers have expressed cautious enthusiasm about the research. "This is a very exciting discovery, but still it has to be confirmed by other teams, other techniques, more statistics and so on," says Joachim Wambsganss of the University of Heidelberg in Germany, who wrote a commentary accompanying the research in Nature. "It's plausible" that these planetlike objects are indeed adrift in the galaxy rather than simply loosely bound to a star, Wambsganss says. "I wouldn't say it's proved. I wouldn't bet my house on it, let me put it this way, but it's pretty convincing."

Microlenses for Macro Objects
MOA and OGLE look for so-called microlensing events in the night sky. Microlensing occurs when a chance alignment brings an otherwise unseen celestial object between Earth and a distant background star. The celestial object's mass bends light rays from the background star, focusing the light like a magnifying lens toward Earth and making the background star appear temporarily brighter. Those events are rare, so microlensing searches monitor large numbers of stars for long periods of time; the new discovery came out of a MOA survey of 50 million stars in 2006 and 2007.

The duration of a microlensing event indicates the mass of the celestial object that acts as the lens. The MOA group found 10 microlensing events that lasted less than two days, which points to a lens of at most a few times Jupiter's mass. The independent OGLE group broadly confirmed that finding. But none of the objects were accompanied by a stronger lensing signal indicating a more massive host star nearby. So either the objects are drifting alone through the galaxy or they orbit their stars at a great remove. But there seem to be far more of these objects than can be explained by wide-orbit planets, and also far more than can be explained by very lightweight stars or brown dwarfs.

The researchers speculate that these newfound objects may have formed in relatively ordinary planetary systems before losing a game of gravitational tug-of-war with sibling planets and being flung clear of their birthplaces. "This implies that star formation must be producing many planets that are ejected away from their star," says Pavel Kroupa of the University of Bonn in Germany. Those ejections, Kroupa says, could even be caused by nearby stars perturbing a planetary system. "Clearly any theory of star formation will need to account for this population of free-floating planetary-mass objects," he adds.

Planet or Dwarf?
Free-floating objects in the planetary-mass range have been found before, but they were located in star-forming regions of the galaxy and had a bit more heft than the newfound objects. That led some astronomers to think of them as being more akin to lightweight brown dwarfs than to planets—that is, they probably formed on their own rather than in orbit around a larger parent body. But the newfound objects seem to be solidly in the planetary-mass range and also seem to dot the galaxy, not confining themselves to regions where stars and failed stars such as brown dwarfs are being born.

As to what to call these newfound objects, Wambsganss favors brevity. "I think the most intuitive name is 'free-floating planets,' but if we decide to adopt that name then we have to give up one of our definitions of a planet," he says. "A free-floating planet is a contradiction, because a planet is by definition bound" in an orbit around a star.

That contradiction will no doubt fuel controversy—McCaughrean calls "free-floating planets," a term that appears once in the new study, "a red rag to a bull." Even the more conservative "free-floating planetary-mass objects" can be misleading, McCaughrean says. "To me, that's somewhat still equivalent to calling a Chihuahua a 'cat-massed object,'" he says.

Sumi predicts that his and his colleagues' new discovery will spur discussion at the IAU, much like the 2006 debate that led to Pluto's demotion. "I think that people have not thought seriously about this yet because there is little evidence of these objects so far," he says. So what is Sumi's take? If a celestial object formed just like any other planet, which he and his colleagues suspect is the case for their newfound objects, then he says "it is natural to be called a planet."

Source Scientific American

New SETI survey focuses on Kepler's top Earth-like planets

UC Berkeley uses Green Bank radio telescope to look for signals from advanced civilizations.
 
Now that NASA's Kepler space telescope has identified 1,235 possible planets around stars in our galaxy, astronomers at the University of California, Berkeley, are aiming a radio telescope at the most Earth-like of these worlds to see if they can detect signals from an advanced civilization.

The search began on Saturday, May 8, when the Robert C. Byrd Green Bank Telescope – the largest steerable radio telescope in the world – dedicated an hour to eight stars with possible planets. Once UC Berkeley astronomers acquire 24 hours of data on a total of 86 Earth-like planets, they'll initiate a coarse analysis and then, in about two months, ask an estimated 1 million SETI@home users to conduct a more detailed analysis on their home computers.

"It's not absolutely certain that all of these stars have habitable planetary systems, but they're very good places to look for ET," said UC Berkeley graduate student Andrew Siemion.
The Green Bank telescope will stare for about five minutes at stars in the Kepler survey that have a candidate planet in the star's habitable zone – that is, the planet has a surface temperature at which liquid water could be maintained.

"We've picked out the planets with nice temperatures – between zero and 100 degrees Celsius – because they are a lot more likely to harbor life," said physicist Dan Werthimer, chief scientist for SETI@home and a veteran SETI researcher.

Werthimer leads a 30-year-old SETI project on the world's largest radio telescope, the Arecibo receiver in Puerto Rico, which feeds data to SETI@home for a detailed analysis that could only be done on the world's largest distributed computer. He was involved in an early SETI project with the previous Green Bank telescope, which collapsed in 1988, as well as with the Allen Telescope Array (ATA) , which also conducted a broader search for intelligent signals from space run by the SETI Institute of Mountain View, Calif. The ATA went into hibernation mode last month after the SETI Institute and UC Berkeley ran out of money to operate it.

"With Arecibo, we focus on stars like our sun, hoping that they have planets around them that emit intelligent signals," Werthimer said. "But we've never had a list of planets like this before."
The radio dish in rural West Virginia was needed for the new search because the Arecibo dish cannot view the area of the northern sky on which Kepler focuses. But the Green Bank telescope also offers advantages over Arecibo. UC Berkeley's SETI observations piggyback on other astronomical observations at Arecibo, and is limited in the wavelength range it can observe, which centers on the 21 centimeter (1420 MHz) line where hydrogen emits light. These wavelengths easily pass through the dust clouds that obscure much of the galaxy.
"Searching for ET around the 21 centimeter line works if civilizations are broadcasting intentionally, but what if planets are leaking signals like 'I Love Lucy'?" Werthimer said. "With a new data recorder on the Green Bank telescope, we can scan a 800 megaHertz range of frequencies simultaneously, which is 300 times the range we can get at Arecibo."

Thus, one day on the Green Bank telescope provides as much data as one year's worth of observations at Arecibo: about 60 terabytes (60,000 gigabytes) in all, Siemion said. If they recorded a similar chunk of the radio spectrum from Arecibo, SETI@home would be overwhelmed with data, since the Arecibo sky survey observes nearly full time for years on end.
"It's also great that we will completely span the water hole, a canonical place to look for intentional signals from intelligent civilizations," Siemion said.

The water hole is a relatively quiet region of the radio spectrum in the universe and a range of wavelengths not significantly absorbed by material between the stars and galaxies. The water hole is bounded on one end by the 21 cm emissions from neutral hydrogen and on the other by the 18 cm emissions from the hydroxyl ion (OH). Because life is presumed to require the existence of liquid water, and water is composed of hydrogen and hydroxyl, this range was dubbed the water hole and seen as a natural window in which water-based life forms would signal their existence. That makes the water hole is a favorite of SETI projects.
"This is an interesting place, perhaps a beacon frequency, to look for signals from extraterrestrial civilizations," Siemion added.

The 86 stars were chosen from the 1,235 candidate planetary systems – called Kepler Objects of Interest, or KOIs with the help of Kepler team member Geoffrey Marcy, professor of astronomy at UC Berkeley. UC Berkeley's targets include the 54 KOIs identified by the Kepler team as being in the habitable temperature range and with sizes ranging from Earth-size to larger than Jupiter; 10 KOIs not on the Kepler team's habitable list but with orbits less than three times Earth's orbit and orbital periods greater than 50 days; and all systems with four or more possible planets.

After the Green Bank telescope has targeted each star, it will scan the entire Kepler field for signals from planets other than the 86 targets.
A coarse analysis of the data by Werthimer and his team will be followed by a more thorough analysis by SETI@home users, who will be able to see whether they are analyzing Green Bank data as opposed to Arecibo data. The complete analysis for intelligent signals could take a year, Werthimer said.
"If you extrapolate from the Kepler data, there could be 50 billion planets in the galaxy," he said. "It's really exciting to be able to look at this first batch of Earth-like planets."

Source EurekaAlert!

Fundamental question on how life started solved

German and US researchers calculate a carbon nucleus of crucial importance

The researchers published their results in the coming issue of the scientific journal Physical Review Letters.

"Attempts to calculate the Hoyle state have been unsuccessful since 1954," said Professor Dr. Ulf-G. Meißner (Helmholtz-Institut für Strahlen- und Kernphysik der Universität Bonn). "But now, we have done it!" The Hoyle state is an energy-rich form of the carbon nucleus. It is the mountain pass over which all roads from one valley to the next lead: From the three nuclei of helium gas to the much larger carbon nucleus. This fusion reaction takes place in the hot interior of heavy stars. If the Hoyle state did not exist, only very little carbon or other higher elements such as oxygen, nitrogen and iron could have formed. Without this type of carbon nucleus, life probably also would not have been possible.

The search for the "slave transmitter"

The Hoyle state had been verified by experiments as early as 1954, but calculating it always failed. For this form of carbon consists of only three, very loosely linked helium nuclei - more of a cloudy diffuse carbon nucleus. And it does not occur individually, only together with other forms of carbon. "This is as if you wanted to analyze a radio signal whose main transmitter and several slave transmitters are interfering with each other," explained Prof. Dr. Evgeny Epelbaum (Institute of Theoretical Physics II at Ruhr-Universität Bochum). The main transmitter is the stable carbon nucleus from which humans - among others - are made. "But we are interested in one of the unstable, energy-rich carbon nuclei; so we have to separate the weaker radio transmitter somehow from the dominant signal by means of a noise filter."

What made this possible was a new, improved calculating approach the researchers used that allowed calculating the forces between several nuclear particles more precisely than ever. And in JUGENE, the supercomputer at Forschungszentrum Jülich, a suitable tool was found. It took JUGENE almost a week of calculating. The results matched the experimental data so well that the researchers can be certain that they have indeed calculated the Hoyle state.

More about how the Universe came into existence

"Now we can analyze this exciting and essential form of the carbon nucleus in every detail," explained Prof. Meißner. "We will determine how big it is, and what its structure is. And it also means that we can now take a very close look at the entire chain of how elements are formed."

In future, this may even allow answering philosophical questions using science. For decades, the Hoyle state was a prime example for the theory that natural constants must have precisely their experimentally determined values, and not any different ones, since otherwise we would not be here to observe the Universe (the anthropic principle). "For the Hoyle state this means that it must have exactly the amount of energy it has, or else, we would not exist," said Prof. Meißner. "Now we can calculate whether - in a changed world with other parameters - the Hoyle state would indeed have a different energy when comparing the mass of three helium nuclei." If this is so, this would confirm the anthropic principle.

###

The study was jointly conducted by the University of Bonn, Ruhr-Universität Bochum, North Carolina State University, and Forschungszentrum Jülich.

Source EurekaAlert!

NASA floats Titan boat concept

The TiME mission would send a flying-saucer-shaped probe to float in Ligeia Mare, a 400-kilometre-long hydrocarbon lake on Titan (Image: NASA/JPL/USGS).

No one has ever floated a boat on another world, but NASA is now considering doing just that, on Saturn's icy moon Titan. Probing the moon's hydrocarbon lakes could reveal clues to its climate and perhaps even signs of exotic life forms.

Titan's surface is dotted with lakes, making it strangely reminiscent of Earth. But rather than water, the lakes are filled with a mixture of methane and ethane, which are gases on Earth but are liquid at Titan's surface temperature of -180 °C.

NASA is now considering sending a probe to splash down into one of the lakes. It has selected a mission called the Titan Mare Explorer (TiME) as one of three finalists competing for a chance to fly in 2016. The TiME project is led by Ellen Stofan of Proxemy Research in Gaithersburg, Maryland.

In 2023, after a seven-year cruise from Earth, TiME would parachute into a lake in Titan's northern hemisphere called Ligeia Mare. Powered by heat from the decay of an onboard plutonium supply, the probe would bob around the lake's surface and make measurements for about three months.

Titan is the only place in the solar system that appears to have a cycle analogous to the water cycle on Earth, with hydrocarbon rain depositing liquid on the surface, followed by evaporation and more rain.

Rain-lashed probe?

TiME would help reveal details about this cycle by measuring the temperature, humidity and winds at the surface of the lake. With luck, it could be the first probe to experience rain on another world. The probe would also snap pictures of the lake's surface and shorelines and peer up at clouds in the sky.

Though it lacks a means of propulsion, the flying-saucer shaped probe should gradually drift with the breeze, allowing it to sample different parts of the lake. As it did so, it could measure the lake's depth with sonar and taste the brew of chemicals it contains with a mass spectrometer.

That would provide a new window into Titan's intriguing chemistry. Complex carbon-based, or organic, molecules, such as acetylene, are known to form in abundance in the moon's atmosphere and rain down onto the surface.

The organic molecules are likely to get mixed into the lakes and might undergo further chemical reactions there. Some scientists have even speculated that microscopic life forms could live in the lakes, eating acetylene and breathing hydrogen gas.

Searching for signs of life

With its mass spectrometer, TiME would explore any interesting chemistry going on in the lake. If any life is present, it might produce unusual patterns in the abundance of organic molecules.

"Titan is an endpoint on exploring what are the limits to life in our solar system," Stofan told New Scientist. "We're going to be looking for patterns in abundances of compounds to look for evidence for more complex or interesting reactions."

But in order to fly, TiME will have to out-compete two other proposed missions: a seismic monitoring station for Mars and a probe that would hop around the surface of a comet.

NASA has awarded $3 million to each of the three competing teams to flesh out their mission concepts. After a review in 2012, the agency plans to decide which mission will receive the $425 million it needs to fly.

Source New Scientist

Fountains of Optimism for Life Way Out There

Ontario Lacus is a large lake on Saturn's moon Titan.

For those who hunt for life on other worlds, water in its liquid form is perhaps the leading indicator. Life as we know it on Earth is based on water and carbon. And if organisms can prosper here in nasty environments — in geysers, in the depths of the sea, in toxic waste, in water that is too hot, too cold, too acidic or too alkaline — why could they not prosper out there?

Scientists for years regarded liquid water as a solar system rarity, for there was no place apart from Earth that seemed to have the necessary physical attributes, except perhaps Jupiter’s ice-covered moon, Europa, which probably concealed a subterranean ocean.

The past 20 years of space exploration, however, have caused what the astrobiologist David Grinspoon calls a sea change in thinking. It now appears that gravity, geology, radioactivity and antifreeze chemicals like salt and ammonia have given many “hostile” worlds the ability to muster the pressures and temperatures that allow liquid water to exist. And research on Earth has shown that if there is water, there could be life.

On Mars and Venus, on Saturn’s moons Enceladus and Titan, and even on two outer-belt asteroids, researchers have shown that the presence of liquid water is possible and even likely. Proof of life, of course, will come only when something — or someone — puts a drop of alien water under a microscope and sees a microbe.

“Water and carbon-based life works well,” Dr. Grinspoon said. “That doesn’t mean it’s the only way, but it’s the only way we know, and it gives us something to look for.”

Finding water in space, in the form of ice, has never been a problem. Hydrogen is the most common element in the solar system, and oxygen is not far behind. When the solar system formed about 4.5 billion years ago, a spiraling disc of dust and gas spun out from the Sun to produce the planets, their moons, and an enormous cloud of comets, planetoids and other bits of cosmic flotsam. Nature endowed much of this debris with a generous helping of water ice.

Liquid water is another matter. The heat of the Sun may melt the ice, but in the vacuum of space there is little or nothing on the surface of most solar system objects to keep the heated molecules together, so they flash instantly away as water vapor. This process is called sublimation.

The physics of sublimation are unforgiving. Liquid water needs a delicate balance of temperature and pressure. Ice must be able to melt without boiling off, but the water must stay warm enough that it does not refreeze. On Earth, with a sea level atmospheric pressure of 14.7 pounds per square inch, water is liquid between 32 and 212 degrees Fahrenheit. On the unshadowed parts of our Moon, where the atmospheric pressure is zero and daytime temperatures can exceed 260 degrees Fahrenheit, the surface ice is long gone.

Ice survives at very low temperatures, however, and the chunks of debris that linger in the chill reaches of deep space beyond Neptune make up the biggest source of water in the solar system today. These dirty snowballs re-enter the planetary system periodically as comets. When they get close enough to the Sun, the ice begins to sublimate, giving the comets their characteristic tail of dust and water vapor.

Many scientists say it is likely that much of the ice in the inner solar system came from comets. On Earth, cometary impacts early in the planet’s history could have provided this raw material, and the Sun and atmospheric pressure would have done the rest. Earth is the only place in the solar system so far discovered where liquid is the default state of surface water. And Earth is where life proliferates.

But it is maybe not the only place. Dr. Grinspoon has theorized that Venus, whose spectacular volcanism boiled off all its surface water long ago, nevertheless harbored liquid moisture in the noxious clouds of sulfuric acid that cloak the planet. In 2008 the European Space Agency’s Venus Express orbiter measured water vapor in the clouds. About 30 miles above the surface in the Venusian mist, where temperatures are about 70 degrees Fahrenheit, extremophiles could find a comfort zone.

Another improbable venue for liquid water is the outer limits of the asteroid belt between Mars and Jupiter. There, using infrared telescopes, two teams of astronomers working separately in 2008 and 2009 found water ice on the surface of the asteroid 24 Themis, about 280 million miles from the Sun. Last year, the teams joined forces and found ice on a second asteroid, 65 Cybele, which, with a diameter of 180 miles, was about 1.5 times as large as 24 Themis and 45 million miles farther out.

For ice to endure on like objects with no atmosphere that close to the Sun, there must be a mechanism to replenish what is lost to sublimation. Humberto Campins, a University of Central Florida astrophysicist and leader of one of the discovery teams, suggested that the patchy ice was a thin coating of frost from a reservoir hidden below the asteroids’ topsoil regolith.

When the asteroid faced the Sun, heat penetrated the topsoil, causing subsurface ice to sublimate and migrate as water vapor to the surface, where it froze at night only to sublimate again during the day. In a variation on this theme, Dr. Campins said, meteorites could be churning up the asteroid topsoil, thus bringing ice closer to the surface. This process is called “impact gardening.”

“We suspect that something like this is happening,” Dr. Campins said, but acknowledged a third possibility: The asteroids could contain enough radioactive isotopes to melt ice deep below the surface, creating liquid water that seeps upward before vaporizing.

“You need sufficient pressure and temperature,” he said. “But conceptually it’s possible.” Pressure would come from the asteroids’ interior gravity, allowing water to exist once the isotopes melt the ice.

Radioactivity is a widespread phenomenon and a likely source of heat energy elsewhere in the solar system. Another heat source is friction, caused most commonly by tidal pressure or wobbling of an object on its axis.

The evidence that Jupiter’s moon Europa harbors an enormous liquid ocean beneath its icy shell has arisen in part from observations suggesting that tidal forces create heat by stretching and compressing the moon as it rotates around Jupiter in an eccentric orbit.

Recently scientists have been able to study tidal forces up close during fly-bys of Saturn’s moon Enceladus by NASA’s Cassini spacecraft. In 2005 Cassini found that Enceladus, with a diameter of only 300 miles, was spewing water ice grains from cracks in its south polar region. The grains were the “dust” that formed Saturn’s E-ring, and scientists soon began to suspect strongly that the particles came from a subsurface liquid water source.

“I wouldn’t say it’s virtually certain, but I’d give it 80 percent or 90 percent,” said John Spencer, a planetary scientist at the Southwest Research Institute, a member of Cassini’s composite infrared spectrometer team. “Things may be a lot stranger than we imagine, but basically, I suspect we have an ocean.”

More disputed is the theory that low-temperature “cryo-volcanoes” on Saturn’s largest moon, the hydrocarbon-rich Titan, may be belching slushy lava composed of liquid water and ammonia, or some other low-temperature mixture, that freezes on the moon’s surface.

“Titan has hydrocarbon sand dunes and methane lakes, and the cryo-volcanism could be hydrocarbon,” said Jeffrey Kargel, a University of Arizona planetary scientist. “We would have to go there to know for sure.” Still, he added, “there pretty much has to be water ice” on Titan, since there is ice everywhere else in the solar system where it is cold enough. Titan has a regular orbit, so tidal friction would be minimal. For liquid water to exist, there would have to be a radioactive heat source and antifreeze compounds.

Antifreeze is what Nilton Renno of the University of Michigan was looking for to explain the unforeseen event that befell NASA’s Phoenix Lander on the arctic plains of Mars in 2008. Hydrazine thrusters that arrested the lander’s descent had blown aside seven inches of Martian topsoil, exposing the expected layer of ice that lay below.

But four days later, something unexpected happened. Cameras examining the ice discerned a number of blisterlike globules on one of the spacecraft struts. A few days after that, the camera looked again. The globules remained.

Although Dr. Renno, the atmospheric science team leader for Phoenix, did not immediately report it, he suspected he was observing droplets of liquid water. It would have to be salty enough not to vaporize in the Martian atmosphere or freeze at surface temperatures below minus 22 degrees Fahrenheit.

For that there needed to be antifreeze. Salt was the likeliest source: “Suppose you have a swimming pool, and you fill it with saltwater,” Dr. Renno said. “When the pool cools down and starts to freeze, pure water becomes ice. The remaining water becomes more saline. It becomes harder to freeze as the salt concentration becomes stronger.”

Evidence arrived in two steps. First, the lander’s instruments found high salt concentrations in soil surrounding the spacecraft. Then, three weeks after touchdown, the Lander’s robotic arm dug a trench in the ice and encountered a soft layer that contrasted with nearby hard ice patches that the lander penetrated with a drill. The slush was a second source of water, and like the first, “probably filled with salt,” Dr. Renno said. “It was almost like ice cream.”

Meanwhile, “we kept taking pictures” of the strut, and 44 days after touchdown the largest droplet disappeared, Dr. Renno recalled. “It grew too large, and dripped off.”

Source New York Times