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Exoplanets (Extra-Solar Planets)

Four new exoplanets to start off the new year!
January 6th, 2012 in Space & Earth / Astronomy
http://www.physorg.com/news/2012-01-exo ... -year.html

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Artist's conception of a "hot Jupiter" orbiting close to its star. Credit: NASA/JPL-Caltech/T. Pyle (SSC)

It’s only a few days into 2012 and already some new exoplanet discoveries have been announced. As 2011 ended, there were a total of 716 confirmed exoplanets and 2,326 planetary candidates, found by both orbiting space telescopes like Kepler and ground-based observatories. The pace of new discoveries has accelerated enormously in the past few years. Now there are four more confirmed exoplanets to add to the list.

The four planets, HAT-P-34b, HAT-P-35b, HAT-P-36b, HAT-P-37b all have very tight orbits around their (four different) stars, taking only 5.5, 3.6, 1.3 and 2.8 days to complete an orbit. Compare that to Mercury, which takes 87.969 days and 365 days of course for Earth.
They were found by astronomers with the Harvard-Smithsonian Center for Astrophysics which operates a network of ground-based telescopes known as the HATNet project. The first exoplanet discovery by HATNet, the planet HAT-P-1b, was in 2006.
They are all “hot jupiter” type planets, gas giants which orbit very close to their stars and so are much hotter than Earth, like Mercury in our own solar system. Mercury though, of course, is a small rocky world, but in some alien solar systems, gas giants have been found orbiting just as close to their stars, or even closer, than Mercury does here. HAT-P-34b however, may have an “outer component” and is in a very elongated orbit. The other three are more typical hot Jupiters. They were discovered using the transit method, when a planet is aligned in its orbit so that it passes in front of its star, from our viewpoint.
So what does this mean? If exoplanet discoveries continue to grow exponentially as expected, then 2012 should be a good year, not only for yet more new planets being found, but also for our understanding of these alien worlds and how such a wide variety of solar systems came to be. We’ve come a long way from 1992 and the first exoplanet discoveries and things promise to only get more exciting in the future.
More information: The abstract and paper are here.
Source: Universe Today
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Study says every star has planets
By Jason Palmer, Science and technology reporter, BBC News, Austin, Texas

Every star twinkling in the night sky plays host to at least one planet, a new study suggests.
That implies there are some 10 billion Earth-sized planets in our galaxy.

Using a technique called gravitational microlensing, an international team found a handful of exoplanets that imply the existence of billions more.
The findings were released at the 219th American Astronomical Society (AAS) meeting, alongside reports of the smallest "exoplanets" ever discovered.

Gravitational microlensing is a method that uses the gravity of a far-flung star to amplify the light from even more distant stars that have planets.

Astronomers used a number of relatively small telescopes that make up the Microlensing Network for the Detection of Small Terrestrial Exoplanets, or Mindstep, to look for the rare event of one star passing directly in front of another as seen from Earth.
The team witnessed 40 of these microlensing events, and in three instances spotted the effects of planets circling the more distant stars.

While the number of actual events and detected planets was low, the team was able to estimate how many such exoplanets must exist.

Most news of exoplanets in recent years has come from the Kepler telescope, which spots planets by looking for the slight dimming of their host stars' light as planets pass in front of them.
That method is better at finding large planets close to their host stars.

While a more difficult effect to catch, gravitational microlensing is better at finding planets of all sizes and distances.
It can currently spot a planet as small as Mercury, orbiting at a similar distance to its host star, or as far away as Saturn.

The Nature study was a collaboration between researchers from more than 20 international institutes and universities.
"Just the recent 15 years have seen the count of known planets beyond the Solar System rising from none to about 700, but we can expect hundreds of billions to exist in the Milky Way alone." says co-author Dr Martin Dominik, from the University of St Andrews, UK.

However, Kepler measurements hold a number of small-planet surprises as well.
In December, the Kepler team announced the first Earth-sized planet, the smallest yet detected.
Also at the meeting, the Kepler team announced even smaller planets, all three orbiting a small dwarf star called KOI-961.
The planets are just 0.78, 0.73 and 0.57 times the radius of Earth.
The discovery came from an analysis of Kepler catalogue data released to the public in February 2011.

UK amateur astronomer Kevin Apps was among those who pored through the data, finding an unusual looking set of planet candidates in the data.
He contacted long-time collaborator John Johnson, a California Institute of Technology astronomer, and found the key to the puzzle lay in comparing the KOI-961 star to the well-known and similar Barnard's star.
What they found was a miniature version of other mulitple planetary systems that the exoplanet hunt has catalogued.

Using similar parameters, Mr Apps told BBC News, "we realised that it was even more remarkable than we thought: the star was fainter, the planets were smaller. The whole thing was like a very compact triple planetary system."

Prof Johnson said that the trio was "more similar to Jupiter and its moons in scale than any other planetary system".
"The discovery is further proof of the diversity of planetary systems in our galaxy."

http://www.bbc.co.uk/news/science-environment-16515944
 
Another Wisdom of Crowds project:

Volunteers wanted for planet hunt

Members of the public are being asked to join the hunt for nearby planets that could support life.
Volunteers can go to the Planethunters website to see time-lapsed images of 150,000 stars, taken by the Kepler space telescope.
They will be advised on the signs that indicate the presence of a planet and how to alert experts if they spot them.

"We know that people will find planets that are missed by the computer," said Chris Lintott from Oxford University.
"When humans have looked at data, we know they find planets that computers can't."

The Kepler space telescope, launched in 2009, has been searching a part of space thought to have many stars similar to our own Sun.
Its most exciting moment to date has been, the discovery of Kepler 22b, a planet close in size and temperature to Earth, lying about 600 light-years away.

Another nine months of data from the Kepler space telescope is being put online at the Planethunters website to coincide with three consecutive nights of BBC Two's Stargazing Live beginning on Monday 16 January.
"By Wednesday we hope to have some exciting discoveries." said Dr Lintott.

The Planethunters website will have time-lapsed sequences of images of about 150,000 stars which have so far only been available to professional astronomers and their computers.
"We are very confident there are more planets lurking in there to be found," Chris Lintott explained.

Anyone spotting a potential planet can flag up the telltale data and, if a significant planet is found, they would be credited with the discovery and their name would appear in any subsequent scientific paper about the discovery.

The human brain would be particularly good at finding any weird or unusual systems says Lintott, involving variable or double stars or multiple interacting planets.
Already several planets have been discovered by the public since the site was put live last year by an international team including scientists from Yale and Oxford universities.
But sadly, volunteers cannot get a planet named after them, as planet names are derived from the stars they orbit.

Stargazing Live returns to BBC Two at 2030:GMT on Monday and 20:00 GMT on Tuesday and Wednesday, 16-18 January 2012. Preliminary results of the planet hunt by Stargazing viewers will feature in the final programme.

http://www.bbc.co.uk/news/science-environment-16512017
 
As a follow-up to Rynner's post on 16/01/2012...

The public push initiated on BBC Two's Stargazing Live series to find planets beyond our Solar System has had an immediate result.

A viewer who answered the call has helped spot a world that appears to be circling a star dubbed SPH10066540.

The planet is described as being similar in size to our Neptune and circles its parent every 90 days.

Chris Holmes from Peterborough found it by looking through time-lapsed images of stars on Planethunters.org.

The website hosts data gathered by Nasa's Kepler space telescope, and asks volunteers to sift the information for anything unusual that might have been missed in a computer search.

"I've never had a telescope. I've had a passing interest in where things are in the sky, but never had any more knowledge about it than that," Mr Holmes told BBC News.

"Being involved in a project like this and actually being the one to find something is a very exciting position."

Chris Lintott from Oxford University who helps organise Planethunters.org added: "We're ecstatic. We've been groaning under the strain of all these people who want to help us, which is exactly how it should be."

The public participation project was launched last year, but it got a huge fillip when it was featured in the popular Stargazing series' return to BBC Two on Monday.

Volunteers have tripled to more than 100,000 people, and the number of images inspected has now reached a million.

The new planet candidate's status will need more checking, but it looks strong, said Dr Lintott.

"It would be our fifth detection since we started and our first British one as well," he added.

The Kepler space telescope, launched in 2009, has been searching a part of space thought to have many stars similar to our own Sun.

It looks for the periodic dip in light that results every time a planet passes in front of one of those stars.
Kepler data A tell-tale: A planet passing in front of a star will result in a dip in light detected by Kepler

These so-called transit have to be observed several times before a planet will be confirmed. For the orange dwarf star SPH10066540, five such events have now been seen in the Kepler data.

Mr Holmes found a pass; the Planethunters team then looked deeper into the Kepler archive and found it had made other transits before and after.

The candidate has a radius about 3.8 times that of Earth, and orbits its parent star at a distance of 55 million km - a separation similar to that between Mercury and our Sun.

This means the planet is probably too hot to support life.

"Kepler is trying to answer the question: 'how many planets are there in our Milky Way Galaxy?'" explained Dr Lintott.

"Now, you can build an algorithm to search through the data but the chances are it will have some systematics - it may be missing some things. Planethunters is the ultimate check. If the computers don't find the planets, the humans will; and it helps us to be sure that we're getting a true picture of the planet population in the Milky Way."

BBC Source
 
Fomalhaut's giant exoplanet may be small lava world
http://www.newscientist.com/article/dn2 ... world.html
16:34 02 February 2012 by Lisa Grossman

One of the first exoplanets to be imaged directly is not the plain Jane it seemed. Instead, it may be a rocky planet covered with lava.

Most planets are too small, dim and close to their parent stars to be photographed. But Hubble Space Telescope images from 2004 and 2006 revealed a Jupiter-like dot around the star Fomalhaut, which lies 25 light years away. The apparent planet, named Fomalhaut b, appeared inside a gap in a dusty disc surrounding the star, suggesting it had carved out the space during its orbits.

Early on, though, the dot exhibited behaviour unbecoming of a planet, dropping in brightness by a factor of two between 2004 and 2006.

"It immediately struck me as weird," says Markus Janson of Princeton University. "I thought something more complex must be going on here than, 'There's light from a planet.'"

Now Janson and his colleagues have analysed new infrared observations – the most sensitive yet – made by NASA's Spitzer Space Telescope. They found nothing at the wavelengths where a Jupiter-sized planet should be brightest.

"There's really no wiggle room left for claiming that Fomalhaut b is a directly imaged [Jupiter-sized] planet," says Ray Jayawardhana of the University of Toronto, Canada.

Spitzer is not sensitive enough to detect objects smaller than Jupiter, opening up a Pandora's box of new possibilities.

Small, small world?

Fomalhaut b's discoverer, Paul Kalas of the University of California, Berkeley, thinks it might be an exo-Saturn – a ringed planet about a third the size of Jupiter. It would be too small for Spitzer to see, but would be brighter than expected for its size at visible wavelengths because its ring system would reflect its star's light.

"We have in our solar system an example of what we're proposing for Fomalhaut b," Kalas says. "That's not proof of anything, but it's a plausibility argument."

Janson thinks the bright speck orbiting Fomalhaut is more likely to be a transient dust cloud kicked up by colliding asteroids. That would explain why its brightness has faded and suggests it will only get fainter with time.

However, there is another, more brutal possibility. Fomalhaut b might be a rocky planet up to 10 times the mass of the Earth that is being beaten to a molten mess by incoming meteoroids, Janson says. The violence would make it bright at visible wavelengths, but as its surface cools, it should fade – in line with the observations.

"You could have this super-Earth-type planet being very, very heavily pummelled, so hot that its surface melts, and it becomes basically a lava planet," Janson says. "In principle you could then get something small enough and hot enough [to] explain what you observe."

If that is borne out, rather than being the planet that wasn't, Fomalhaut b could be the smallest exoplanet to have its picture taken.

Journal reference: arxiv.org/abs/1201.4388; the work will be published in a future edition of The Astrophysical Journal
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Distant 'waterworld' is confirmed

Astronomers have confirmed the existence of a new class of planet: a waterworld with a thick, steamy atmosphere.
The exoplanet GJ 1214b is a so-called "Super Earth" - bigger than our planet, but smaller than gas giants such as Jupiter.
Observations using the Hubble telescope now seem to confirm that a large fraction of its mass is water.

The planet's high temperatures suggest exotic materials might exist there.
"GJ 1214b is like no planet we know of," said lead author Zachory Berta, from the Harvard Smithsonian Center for Astrophysics.

The planet was discovered in 2009 by ground-based telescopes. It is about 2.7 times the Earth's diameter and weighs almost seven times as much. It orbits its red-dwarf star at a distance of just two million km, meaning temperatures on GJ 1214b probably reach above 200C.

In 2010, astronomers released measurements of its atmosphere. These suggested that GJ 1214b's atmosphere was probably made up of water, but there was another possibility - that the planet was covered in a haze, of the type that envelopes Saturn's moon Titan.

Mr Berta and his colleagues used the Hubble Space Telescope's wide-field camera to study the planet as it crossed in front of its star - a transit. During these transits, the star's light is filtered through the planet's atmosphere, giving clues to the mixture of gases present.
The researchers said their results are more consistent with a dense atmosphere of water vapour, than one with a haze.

Calculations of the planet's density also suggest that GJ 1214b has more water than Earth. This means the internal structure of this world would be very different to that of our own.
"The high temperatures and pressures would form exotic materials like 'hot ice' or 'superfluid water', substances that are completely alien to our everyday experience," said Dr Berta.

The planet's short distance from Earth makes it a likely candidate for follow-up observations with the James Webb Space Telescope, which may launch by the end of this decade.

The study has been accepted for publication by the Astrophysical Journal.

http://www.bbc.co.uk/news/science-environment-17117030
 
We have a name for this kind of world in Orion's Arm; Pyrohydrothallasic. The water on such a world would be hundreds of kilometres deep, ranging from a hot, high pressure ice mantle to a layer of supercritical steam, with a hot water ocean in between. It would be extraordinarily difficult to colonise such a world, since there would be no easily definable surface between the liquid water and the supercritical steam atmosphere,and most of the mineral resources would be locked underneath the ice mantle.

But something like a water-breathing dolphin might thrive there, if they could stand the heat. Even the most optimistic astrobiologist finds it hard to imagine a protein-based biochemistry that can withstand temperatures of above 200 C.
 
ScienceShot: 'Super Earths' Abound Nearby
http://news.sciencemag.org/sciencenow/2 ... tml?ref=hp
by Sid Perkins on 28 March 2012, 6:00 AM | 3 Comments

Credit: ESO/L. Calçada

Tens of billions of small, rocky planets orbiting red dwarf stars inhabit the Milky Way, and dozens lie within 30 light-years of Earth, according to a new survey. Between February 2003 and April 2009, researchers at the European Southern Observatory's La Silla Observatory in Chile studied 102 Class M, so-called red dwarf, stars less than about 32.6 light-years away—a proximity that allowed researchers to detect subtle wobbles that would be induced by one or more planets orbiting the star. Of the stars they scrutinized, the researchers found that eight hosted 14 planets, including 12 estimated to be "super-Earths," rocky planets with a mass between one and 10 times that of our own. Then, accounting for planets in orbits that wouldn't induce detectable wobbles, such as those not seen edge-on from Earth, and for the orbital periods of those planets around their parent stars, the team estimated that about 41% of red dwarf stars have super-Earths orbiting at a distance at which surface water would be liquid—including Gliese 667 Cc (artist's concept above), a super-Earth orbiting one star in a three-star system about 22 light-years from Earth. Considering that about 80%, or 160 billion, of the Milky Way's stars are red dwarfs, there are likely more than 65 billion stars in our galaxy with a habitable super-Earth, the researchers report in a forthcoming issue of Astronomy & Astrophysics, and about 100 of them lie within 10 parsecs, or 32.6 light-years, of Earth.
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Some doubts.


Expectation of extraterrestrial life built more on optimism than evidence, study finds
http://phys.org/news/2012-04-extraterre ... dence.html
April 26th, 2012 in Space & Earth / Space Exploration

(Phys.org) -- Recent discoveries of planets similar to Earth in size and proximity to the planets' respective suns have sparked scientific and public excitement about the possibility of also finding Earth-like life on those worlds.

But Princeton University researchers have found that the expectation that life — from bacteria to sentient beings — has or will develop on other planets as on Earth might be based more on optimism than scientific evidence.

Princeton astrophysical sciences professor Edwin Turner and David Spiegel, a former Princeton postdoctoral researcher, analyzed what is known about the likelihood of life on other planets in an effort to separate the facts from the mere expectation that life exists outside of Earth. The researchers used a Bayesian analysis — which weighs how much of a scientific conclusion stems from actual data and how much comes from the prior assumptions of the scientist — to determine the probability of extraterrestrial life once the influence of these presumptions is minimized.

Turner and Spiegel, who is now at the Institute for Advanced Study, reported in the Proceedings of the National Academy of Sciences that the idea that life has or could arise in an Earth-like environment has only a small amount of supporting evidence, most of it extrapolated from what is known about abiogenesis, or the emergence of life, on early Earth. Instead, their analysis showed that the expectations of life cropping up on exoplanets — those found outside Earth's solar system — are largely based on the assumption that it would or will happen under the same conditions that allowed life to flourish on this planet.

In fact, the researchers conclude, the current knowledge about life on other planets suggests that it's very possible that Earth is a cosmic aberration where life took shape unusually fast. If so, then the chances of the average terrestrial planet hosting life would be low.

"Fossil evidence suggests that life began very early in Earth's history and that has led people to determine that life might be quite common in the universe because it happened so quickly here, but the knowledge about life on Earth simply doesn't reveal much about the actual probability of life on other planets," Turner said.
"Information about that probability comes largely from the assumptions scientists have going in, and some of the most optimistic conclusions have been based almost entirely on those assumptions," he said.

Turner and Spiegel used Bayes' theorem to assign a sliding mathematical weight to the prior assumption that life exists on other planets. The "value" of that assumption was used to determine the probability of abiogenesis, in this case defined as the average number of times that life arises every billion years on an Earth-like planet. Turner and Spiegel found that as the influence of the assumption increased, the perceived likelihood of life existing also rose, even as the basic scientific data remained the same.
"If scientists start out assuming that the chances of life existing on another planet as it does on Earth are large, then their results will be presented in a way that supports that likelihood," Turner said. "Our work is not a judgment, but an analysis of existing data that suggests the debate about the existence of life on other planets is framed largely by the prior assumptions of the participants."

Joshua Winn, an associate professor of physics at the Massachusetts Institute of Technology, said that Turner and Spiegel cast convincing doubt on a prominent basis for expecting extraterrestrial life. Winn, who focuses his research on the properties of exoplanets, is familiar with the research but had no role in it.

"There is a commonly heard argument that life must be common or else it would not have arisen so quickly after the surface of the Earth cooled," Winn said. "This argument seems persuasive on its face, but Spiegel and Turner have shown it doesn't stand up to a rigorous statistical examination — with a sample of only one life-bearing planet, one cannot even get a ballpark estimate of the abundance of life in the universe.

"I also have thought that the relatively early emergence of life on Earth gave reasons to be optimistic about the search for life elsewhere," Winn said. "Now I'm not so sure, though I think scientists should still search for life on other planets to the extent we can."
Promising planetary finds

Deep-space satellites and telescope projects have recently identified various planets that resemble Earth in their size and composition, and are within their star's habitable zone, the optimal distance for having liquid water.
Of particular excitement have been the discoveries of NASA's Kepler Space Telescope, a satellite built to find Earth-like planets around other stars. In December 2011, NASA announced the first observation of Kepler-22b, a planet 600 light years from Earth and the first found within the habitable zone of a Sun-like star. Weeks later, NASA reported Keplers-20e and -20f, the first Earth-sized planets found orbiting a Sun-like star. In April 2012, NASA astronomers predicted that the success of Kepler could mean that an "alien Earth" could be found by 2014 — and on it could dwell similar life.
While these observations tend to stoke the expectation of finding Earth-like life, they do not actually provide evidence that it does or does not exist, Spiegel explained. Instead, these planets have our knowledge of life on Earth projected onto them, he said.

Yet, when what is known about life on Earth is taken away, there is no accurate sense of how probable abiogenesis is on any given planet, Spiegel said. It was this "prior ignorance," or lack of expectations, that he and Turner wanted to account for in their analysis, he said.
"When we use a mathematical prior that truly represents prior ignorance, the data of early life on Earth becomes ambiguous," Spiegel said.
"Our analysis suggests that abiogenesis could be a rather rapid and probable process for other worlds, but it also cannot rule out at high confidence that abiogenesis is a rare, improbable event," Spiegel said. "We really have no idea, even to within orders of magnitude, how probable abiogenesis is, and we show that no evidence exists to substantially change that."

Considering the source

Spiegel and Turner also propose that once this planet's history is considered, the emergence of life on Earth might be so distinct that it is a poor barometer of how it occurred elsewhere, regardless of the likelihood that such life exists.

In a philosophical turn, they suggest that because humans are the ones wondering about the emergence of life, it is possible that we must be on a planet where life began early in order to reach a point so soon after the planet's formation 4.5 billion years ago where we could wonder about it.

Thus, Spiegel and Turner explored how the probability of exoplanetary abiogenesis would change if it turns out that evolution requires, as it did on Earth, roughly 3.5 billion years for life to develop from its most basic form to complex organisms capable of pondering existence. If that were the case, then the 4.5 billion-year-old Earth clearly had a head start. A planet of similar age where life did not begin until several billion years after the planet formed would have only basic life forms at this point.

"Dinosaurs and horseshoe crabs, which were around 200 million years ago, presumably did not consider the probability of abiogenesis. So, we would have to find ourselves on a planet with early abiogenesis to reach this point, irrespective of how probable this process actually is," Spiegel said. "This evolutionary timescale limits our ability to make strong inferences about how probable abiogenesis is."

Turner added, "It could easily be that life came about on Earth one way, but came about on other planets in other ways, if it came about at all. The best way to find out, of course, is to look. But I don't think we'll know by debating the process of how life came about on Earth."

Again, said Winn of MIT, Spiegel and Turner offer a unique consideration for scientists exploring the possibility of life outside of Earth.

"I had never thought about the subtlety that we as a species could never have 'found' ourselves on a planet with a late emergence of life if evolution takes a long time to produce sentience, as it probably does," Winn said.
"With that in mind," he said, "it seems reasonable to say that scientists cannot draw any strong conclusion about life on other planets based on the early emergence of life on Earth."

This research was published Jan. 10 in the Proceedings of the National Academy of Sciences and was supported by grants from NASA, the National Science Foundation and the Keck Fellowship, as well as a World Premier International Research Center Initiative grant from the Japanese Ministry of Education, Culture, Sports, Science and Technology to the University of Tokyo.

Provided by Princeton University
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for dust thou art, and unto dust shalt thou return.

Newfound exoplanet may turn to dust
http://phys.org/news/2012-05-newfound-exoplanet.html
May 18th, 2012 in Space & Earth / Astronomy

Image: NASA, European Space Agency, Alfred Vidal-Madjar (Institut d'Astrophysique de Paris, CNRS)

Researchers at MIT, NASA and elsewhere have detected a possible planet, some 1,500 light years away, that appears to be evaporating under the blistering heat of its parent star. The scientists infer that a long tail of debris — much like the tail of a comet — is following the planet, and that this tail may tell the story of the planet’s disintegration. According to the team’s calculations, the tiny exoplanet, not much larger than Mercury, will completely disintegrate within 100 million years.

The team found that the dusty planet circles its parent star every 15 hours — one of the shortest planet orbits ever observed. Such a short orbit must be very tight and implies that the planet must be heated by its orange-hot parent star to a temperature of about 3,600 degrees Fahrenheit.

Researchers hypothesize that rocky material at the surface of the planet melts and evaporates at such high temperatures, forming a wind that carries both gas and dust into space. Dense clouds of the dust trail the planet as it speeds around its star.

“We think this dust is made up of submicron-sized particles,” says co-author Saul Rappaport, a professor emeritus of physics at MIT. “It would be like looking through a Los Angeles smog.”

The group’s findings, published in the Astrophysical Journal, are based on data from the Kepler Observatory, a space-based telescope that surveys more than 160,000 stars in the Milky Way. The observatory records the brightness of each star at regular intervals; scientists then analyze the data for signs of new planets outside our own solar system.

A curiously stellar case

Astronomers using the Kepler satellite typically identify exoplanets by looking for regular dips in a star’s brightness. For example, if a star dims every month, one possibility is that the dimming is due to a planet that travels around the star over the course of a month; each time the planet travels in front of the star, the planet blocks the same small amount of light.

However, Rappaport and his colleagues came across a curious light pattern from a star dubbed KIC 12557548. The group examined the star’s light curves, a graph of its brightness over time, and found that its light dropped by different intensities every 15 hours — suggesting that something was blocking the star regularly, but by varying degrees.

The team considered several explanations for the puzzling data, including the possibility that a planetary duo — two planets orbiting each other — also orbited the star. (Rappaport reasoned that the planetary pair would pass by the star at different orientations, blocking out different amounts of light during each eclipse.) In the end, the data failed to support this hypothesis: The dimming every 15 hours was judged far too short a period to allow sufficient room for two planetary bodies orbiting each other, in the same way that Earth and the moon together orbit the sun.

A dusty idea

Instead, the researchers landed on a novel hypothesis: that the varying intensities of light were caused by a somewhat amorphous, shape-shifting body.
“I’m not sure how we came to this epiphany,” Rappaport says. “But it had to be something that was fundamentally changing. It was not a solid body, but rather, dust coming off the planet.”

Rappaport and his colleagues investigated various ways in which dust could be created and blown off a planet. They reasoned that the planet must have a low gravitational field, much like that of Mercury, in order for gas and dust to escape from the planet’s gravitational pull. The planet must also be extremely hot — on the order of 3,600° F.

Rappaport says there are two possible explanations for how the planetary dust might form: It might erupt as ash from surface volcanoes, or it could form from metals that are vaporized by high temperatures and then condense into dust. As for how much dust is spewed from the planet, the team showed that the planet could lose enough dust to explain the Kepler data. From their calculations, the researchers concluded that at such a rate, the planet will completely disintegrate within 100 million years.

The researchers created a model of the planet orbiting its star, along with its long, trailing cloud of dust. The dust was densest immediately surrounding the planet, thinning out as it trailed away. The group simulated the star’s brightness as the planet and its dust cloud passed by, and found that the light patterns matched the irregular light curves taken from the Kepler Observatory.

“We’re actually now very happy about the asymmetry in the eclipse profile,” Rappaport says. “At first we didn’t understand this picture. But once we developed this theory, we realized this dust tail has to be here. If it’s not, this picture is wrong.”

Dan Fabrycky, a member of the Kepler Observatory science team, says the model may add to the many different ways in which a planet can disappear.

“This might be another way in which planets are eventually doomed,” says Fabrycky, who was not involved in the research. “A lot of research has come to the conclusion that planets are not eternal objects, they can die extraordinary deaths, and this might be a case where the planet might evaporate entirely in the future.”

The research was funded by the National Science Foundation and the Natural Sciences and Engineering Research Council of Canada
.
Provided by Massachusetts Institute of Technology

This story is republished courtesy of MIT News

(http://web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.
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'No signal' from targeted ET hunt

The hunt for other intelligent civilisations has a new technique in its arsenal, but its first use has turned up no signs of alien broadcasts.
Australian astronomers used "very long baseline interferometry" to examine Gliese 581, a star known to host planets in its "habitable zone".
The hunt for aliens is fundamentally a vast numbers game, so the team's result should come as no surprise.
Their report, posted online, will be published in the Astronomical Journal.

In recent years, interest in such targeted searches has begun to surge as the hunt for planets outside the Solar System continues to find them at every turn.
Astronomers currently estimate that every star in the night sky hosts, on average, 1.6 planets - implying that there are billions of planets out there yet to be confirmed.

But a number of stars have already been identified as playing host to rocky planets at a distance not too hot and not too cold for liquid water - the first proxy for amenability to life.

Gliese 581, a red dwarf star about 20 light-years away, is a particularly interesting candidate for the Search for Extraterrestrial Intelligence, or Seti.
It has six planets, two of which are "super-Earths" likely to be in this habitable zone.
So astronomers at Curtin University's International Centre for Radio Astronomy Research in Australia, put one of radio astronomy's highest-resolution techniques to work, listening in to the star system.

Very long baseline interferometry (VLBI) is the process of using several or many telescopes that are distant from one another, carefully combining their signals to make them effectively act as one large telescope, peering intently at a tiny portion of the sky.

The team trained the Australian Long Baseline Array onto Gliese 581 for eight hours, listening in on a range of radio frequencies.
The result was radio silence - but the team used their experience to validate VLBI as a technique particularly suited to this kind of targeted search.

Seth Shostak, principal astronomer at the Seti Institute in the US, said that the approach's strength lies in the fraction of the sky it examines.
"It's like they're looking at the sky through a 6-foot-long cocktail straw - a tiny bit of the sky, so they're only sensitive to signals that are coming from right around that star system," he told BBC News.
That is useful not only for getting a high-resolution view, but for excluding the signals from Earthly technologies that plague Seti efforts.

"Figuring out 'is this ET or AT&T?' isn't always easy, and VLBI gives you a good way of discriminating, because if you find something from that tiny, tiny dot on the sky you can say that's not one of our satellites," Dr Shostak said.
He added that the team's negative result was not disheartening, because the odds have it that the hunt for aliens, if it is ever to find them, will require thousands or millions of observations of this kind.

"Consider the fact that you could've looked at the Earth for four billion years with radio antennas - here was a planet that's clearly in the habitable zone, has liquid oceans, and has an atmosphere - and yet unless you had looked in the last 70 years and were close enough, you wouldn't have found any intelligent life," he said.
"The fact that we look at one star system and don't find a signal doesn't tell you that there's no intelligent life."

http://www.bbc.co.uk/news/science-environment-18288926
 
ScienceShot: Alien Earths Have Been Around for a While
http://news.sciencemag.org/sciencenow/2 ... tml?ref=hp
by Govert Schilling on 13 June 2012, 4:00 PM | 1 Comment

Credit: NASA Ames/JPL/Caltech

ANCHORAGE, ALASKA—If there are other species like us in the universe, they've probably been around for a lot longer than we have. According to new research presented here today at the 220th meeting of the American Astronomical Society and published online today in Nature, habitable Earthlike planets orbiting other stars may have formed billions of years before ours did. Earlier, researchers had found that giant, gaseous exoplanets preferably form around stars with a relatively high abundance of heavier elements like iron. Since heavier elements are forged in earlier generations of stars and then dispersed through supernova explosions, Jupiterlike giants must be pretty new to the scene. However, a study of the parent stars of a few hundred smaller exoplanets found by NASA's Kepler space telescope reveals that they have a wide variety of heavy-element abundance. Apparently, small planets can easily form around stars that were born much earlier in the history of the universe. Who knows how many civilizations have already risen and fallen in the cosmic past.
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Proximity of New Planets Stuns Even Astronomers
http://www.sciencedaily.com/releases/20 ... 152307.htm

Artist's conception showing Kepler-36c as it might look from the surface of Kepler-36b. (Credit: David Aguilar, Harvard-Smithsonian Center for Astrophysics)

ScienceDaily (June 21, 2012) — One is a rocky planet 1.5 times the size of Earth. The other is a gaseous world nearly four times Earth's size. Together they form a spectacular system in which two planets orbit closer to each other than any yet discovered.

"We've never known of planets like this," said Yale University astronomer Sarbani Basu, a member of the research team that analyzed the system. "If you were on the smaller planet looking up, the larger planet would seem more than twice the size of Earth's full moon. It would be jaw-dropping."

Basu's research focused on determining the properties of the planets' host star -- work that was essential for discerning the characteristics of the orbiting planets.

The 46-member, international team, led by astronomers at Harvard and the University of Washington, report their discovery June 21 in Science Express, the early release version of the journal Science.

"These two worlds are having close encounters," said Josh Carter, lead author of the paper and a Hubble Fellow at the Harvard-Smithsonian Center for Astrophysics.

Located about 1200 light years away, the two-planet system -- now called Kepler-36 -- orbits a star similar to Earth's sun, but bigger and older.

The larger outer planet, Kepler-36c, is a hot, gaseous, Neptune-like planet. The smaller inner planet, Kepler-36b, is rocky and subject to quakes and volcanic eruptions caused by the interplay of the planets' gravitational forces on each other.

Like our sun, Kepler-36 pulsates constantly. Data on its quakes enabled the team to determine its size, weight, and age (all greater than those of our sun). Knowing the star's radius and mass enabled the calculation of the sizes and masses of the planets. From this information, astronomers could determine the planets' densities and characteristics: the smaller planet is denser than Earth and hence must be rocky; the larger planet is much less dense, in fact less dense than water, suggesting it is gaseous.

"The precise determination of the planets' properties was possible because the star around which they revolve could be characterized precisely," said Basu.

The planets' proximity to each other is astonishing, according to the researchers. The rocky inner planet orbits its star every 14 days, at an average distance of 11 million miles. The outer gaseous planet orbits every 16 days, at an average distance of 12 million miles.

Every 97 days they move into perfect alignment, a position known as conjunction. At that point they are separated by a mere 1.2 million miles -- less than five times the distance between Earth and its moon. By contrast, Venus, Earth's nearest neighbor, never comes closer than 26 million miles.

The research team identified the planets by analyzing data from NASA's Kepler satellite. Kepler detects planets by measuring variations in the brightness of stars; dips in brightness may indicate a planet passing in front the star.

This discovery poses new challenges to the theories of planet formation. Astronomers are now trying to understand how planets with markedly different compositions and densities fell into remarkably close orbit.

NASA and the National Science Foundation supported the research. The national research councils of the United Kingdom, Denmark and the Netherlands also provided support.

Eric Agol of the University of Washington is a co-lead author of the paper.

Story Source:

The above story is reprinted from materials provided by Yale University.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Joshua A. Carter, Eric Agol, William J. Chaplin, Sarbani Basu, Timothy R. Bedding, Lars A. Buchhave, Jørgen Christensen-Dalsgaard, Katherine M. Deck, Yvonne Elsworth, Daniel C. Fabrycky, Eric B. Ford, Jonathan J. Fortney, Steven J. Hale, Rasmus Handberg, Saskia Hekker, Matthew J. Holman, Daniel Huber, Christopher Karoff, Steven D. Kawaler, Hans Kjeldsen, Jack J. Lissauer, Eric D. Lopez, Mikkel N. Lund, Mia Lundkvist, Travis S. Metcalfe, Andrea Miglio, Leslie A. Rogers, Dennis Stello, William J. Borucki, Steve Bryson, Jessie L. Christiansen, William D. Cochran, John C. Geary, Ronald L. Gilliland, Michael R. Haas, Jennifer Hall, Andrew W. Howard, Jon M. Jenkins, Todd Klaus, David G. Koch, David W. Latham, Phillip J. MacQueen, Dimitar Sasselov, Jason H. Steffen, Joseph D. Twicken, and Joshua N. Winn. Kepler-36: A Pair of Planets with Neighboring Orbits and Dissimilar Densities. Science, 21 June 2012 DOI: 10.1126/science.1223269
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New View of Exoplanets Will Aid Search for E.T.
http://www.wired.com/wiredscience/2012/06/tau-bootis-b/
By Adam MannEmail Author June 27, 2012 | 1:34 pm | Categories: Space

Astronomers have developed a new method to probe the atmospheres of extrasolar planets, which should greatly expand the search for planets that have the right temperature and composition for life.

The technique allowed researchers to precisely calculate the mass of a planet named Tau Bootis b for the first time since its discovery 15 years ago.

“The coolest thing about this technique is we basically can now see the planet itself and its orbital movement,” said astronomer Simon Albrecht of MIT, who co-authored a paper describing the method and the Tau Bootis b findings, which appeared June 28 in Nature.

Researchers have several ways of learning about exoplanets. One of the most common and useful methods is used by the Kepler space telescope, which watches to see if the brightness of a star periodically dips, indicating that a planet is passing in front and eclipsing its light. When the exoplanet is just at the star’s edge, starlight can seep through the planet’s atmosphere, carrying a fingerprint of the atmospheric composition when it arrives at telescopes on Earth. Researchers can also sometimes block out a star’s light and directly image an exoplanet, but only when it is farther from its star than Pluto is from our sun.

Alternatively, astronomers closely observe a star to see if it wobbles slightly, signifying that a planet is gravitationally tugging on its host star. With this technique, no light from the planet is typically observed. Albrecht, working with a team led by astronomer Matteo Brogi of Leiden University in the Netherlands, tweaked this later method to get new information about the planet orbiting the star Tau Bootis, a yellow-white star slightly larger and hotter than our sun located 51 light-years away in the constellation Bootes. Since 1996, astronomers have known that Tau Bootis hosts a Jupiter-mass planet that flies around the host star every three days.


By looking carefully at the light coming from Tau Bootis, the researchers were able to tease out certain wavelengths of light that were changing in a characteristic way.

For a day and a half, the wavelengths would get longer, or redshifted, as the planet moved away from us. Then the wavelengths would grow shorter, or blueshifted, for the same amount of time, precisely matching up with the known orbit of the exoplanet. This is known as the Doppler effect, occurring because the frequency of a light or sound wave changes when it’s moving, such as when an ambulance’s pitch increases as it gets closer.

These wobbling wavelengths allowed the team to accurately trace the planet’s orbit, thereby measuring its mass, which is now known to be about six times that of Jupiter. The method also provided information about the planet’s atmosphere, indicating that it contained carbon monoxide.

Soon, the team hopes to look for other molecules, such as methane and hydrogen, and is already applying their technique to probe planets around other stars, said Albrecht. With better telescopes, they may be able to pick up biosignatures such as carbon and oxygen in the atmospheres of Earth-like planets.

“In the future, it will be one of the ways that we can search for these molecules of life,” said Albrecht.

Since only about 1 in 100 exoplanets transit their host star, “we can increase our list of potential targets by a factor of 10 or more,” said planetary scientist Heather Knutson of Caltech, who was not involved in the work. “It really opens up the door for a whole range of exciting measurements.”

But the information gleaned about Tau Bootis’s exoplanet came from one of the most favorable and nearby exoplanets and represents the limit of current telescopes, said astronomer David Charbonneau of Harvard, who was also not involved in the new work.

Truly remarkable results will likely have to wait for the next generation of enormous telescopes, like the Giant Magellan Telescope or the European Extremely Large Telescope, which will be able to pick up far more starlight and probe with higher resolution.

“The main interest for me is not this results in particular, but the results down the road,” said Charbonneau.

Image: An artist’s impression of Tau Bootis b in orbit around its parent star. ESO/L. Calçada
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'Tatooine-like' double-star systems can host planets

A new study shows that planetary systems can form and survive in the chaotic environment around pairs of stars.
A team reports in Science the discovery of two planets orbiting a pair of stars - a so-called binary.

Gravitational disturbances generated by stellar pairs are thought to be very severe for any orbiting planets.
Nasa's Kepler space telescope found two small planets around a pair of low-mass stars.
Such systems have particular significance for science fiction fans. In the Star Wars films, Luke Skywalker's home planet of Tatooine orbits a binary star.

The planetary system, known as Kepler-47, is located roughly 5,000 light-years away, in the constellation Cygnus.
It contains a pair of stars whizzing around each other every 7.5 days. One star is Sun-like, while the other is about one-third the size of its neighbour and 175 times fainter.

Circling the stars is an inner planet about three times larger in diameter than the Earth, and an outer planet that is just slightly larger than Uranus.
The inner planet - dubbed Kepler-47b - takes 49 days to complete an orbit, while the outer planet - Kepler-47c - takes 303 days.

The orbit of the outer planet places it in the so-called "habitable zone", the region around a star where it is neither too cold nor too hot for liquid water to persist on the surface of a planet.

While the outer world is probably a gas-giant planet and thus not suitable for life, its discovery establishes that these "circumbinary" planets can, and do, exist in habitable zones.

A handful of circumbinary planets have been discovered before, but this is the first known planetary system around a pair of stars.
It is thought that gravitational perturbations generated by the binary could either toss planets out of the system, into one of the stars, or fling them into devastating head-on collisions.

"Kepler-47 shows us that typical planetary architectures, with multiple planets in co-planar orbits, can form around two stars," said co-author Joshua Carter, from the Harvard-Smithsonian Center for Astrophysics.
"We've learned that circumbinary planets can be like the planets in our own Solar System, but with two suns."

Prof William Welsh, from San Diego State University, who presented the work at the International Astronomical Union (IAU) meeting in Beijing on behalf of the Kepler Science Team, said: "The thing I find most exciting... is the potential for habitability in a circumbinary system.
"Kepler-47c is not likely to harbour life, but if it had large moons, those would be very interesting worlds."

The Kepler space telescope discovered the planets by measuring the tell-tale drop in brightness they cause when they transit (eclipse) their host stars.
Spectroscopic data from telescopes at McDonald Observatory in Texas enabled the absolute sizes of the planets to be measured.

http://www.bbc.co.uk/news/science-environment-19401891
 
New Exoplanet Is Twice Earth’s Size — And Made Largely of Diamond

By Wired UKEmail AuthorOctober 12, 2012 | 10:00 am | Categories: Space

Illustration of the interior of 55 Cancri e. Image: Haven Giguere
By Liat Clark, Wired UK

A team of astrophysicists has estimated that an exoplanet twice the size of Earth is largely made up of diamond.

The planet, 55 Cancri e, is located around 40 light years from Earth and has a mass eight times that of our planet. With that knowledge in mind, now picture a third of that mass being made up of graphite and diamond. Or just look at the artist’s impression above, created by the team at Yale University and Institut de Recherche en Astrophysique et Planetologie in Toulouse, which represents the ratio of diamond to, well, everything else. Earth, by comparison, has “less than a part in thousand by mass.”
“On this planet there would basically be a thin layer below the surface which will have both graphite and diamond,” lead author on the paper Nikku Madhusudhan told Universe Today. “But, below that there will be a thick layer (a third of the radius) with mostly diamond. For a large part the diamond will be like the diamond on Earth, except really, really pure. But at greater depths the diamond could also be in liquid form.” So once we’ve nailed warp drive and can hop over to the planet, expect the cost of diamonds to plummet significantly.

“This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth,” said Madhusudhan in a press release. “The surface of this planet is likely covered in graphite and diamond rather than water and granite.”


The planet, part of the constellation of Cancer that’s clearly visible from Earth sans binoculars, is the first exoplanet to display these unique properties — in 2011 a “diamond planet” was spotted in the constellation of Serpens, but that planet did not orbit a star similar to our Sun and was not studied in such detail. The two do share certain characteristics, however. For instance, a year on the fast-orbiting 55 Cancri e lasts just 18 hours, while the Milky Way planet’s orbit lasts around two hours.

The team presumably used radio telescope data to determine the mass, diameter and orbit of the 1,648 C-hot 55 Cancri e (the method and results are yet to be published in Astrophysical Journal Letters), which in turn was used to estimate the make-up of the planet. We do know that the team used computer models to estimate possible planetary compositions from the data, with updated information on its mass being key. The most likely explanation for this planet’s formation, the models concluded, is a water-light recipe of carbon — in the form of graphite and diamond — and silicon carbide, which is a combination of silicon and carbon. There will also be smaller amounts of iron.

The find, though providing us with a wonderful mental image, means that in our hunt for Earth-like exoplanets orbiting Sun-like stars, we can expect to find plenty more disappointingly uninhabitable sites, such as the water planet GJ 1214b (another great and satisfying mental image, however).

Source: Wired.co.uk
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http://www.wired.com/wiredscience/2012/ ... exoplanet/
 
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Planet with four suns discovered
By Paul Rincon, Science editor, BBC News website

Astronomers have found a planet whose skies are illuminated by four different suns - the first known of its type.
The distant world orbits one pair of stars and has a second stellar pair revolving around it.

The discovery was made by volunteers using the Planethunters.org website along with a team from UK and US institutes; follow-up observations were made with the Keck Observatory.
A scientific paper has been posted on the Arxiv pre-print server.

The planet, located just under 5,000 light-years away, has been named PH1 after the Planet Hunters site.
It is thought to be a "gas giant" slightly larger than Neptune but more than six times the size of the Earth.

"You don't have to go back too far before you would have got really good odds against one of these systems existing," Dr Chris Lintott, from the University of Oxford, told BBC News.
"All four stars pulling on it creates a very complicated environment. Yet there it sits in an apparently stable orbit.
"That's really confusing, which is one of the things which makes this discovery so fun. It's absolutely not what we would have expected."

Binary stars - systems with pairs of stars - are not uncommon. But only a handful of known exoplanets (planets that circle other stars) have been found to orbit such binaries. And none of these are known to have another pair of stars circling them.

Asked how this planet remained in a stable orbit whilst being pulled on by the gravity of four stars, Dr Lintott said: "There are six other well-established planets around double stars, and they're all pretty close to those stars.

"So I think what this is telling us is planets can form in the inner parts of protoplanetary discs (the torus of dense gas that gives rise to planetary systems).
"The planets are forming close in and are able to cling to a stable orbit there. That probably has implications for how planets form elsewhere."

PH1 was discovered by two US volunteers using the Planethunters.org website: Kian Jek of San Francisco and Robert Gagliano from Cottonwood, Arizona.
They spotted faint dips in light caused by the planet passing in front of its parent stars. The team of professional astronomers then confirmed the discovery using the Keck telescopes on Mauna Kea, Hawaii.

Founded in 2010, Planethunters.org aims to harness human pattern recognition to identify transits in publicly available data gathered by Nasa's Kepler Space Telescope.
Kepler was launched in March 2009 to search for Earth-like planets orbiting other stars.

Visitors to the Planet Hunters website have access to randomly selected data from one of Kepler's target stars.
Volunteers are asked to draw boxes to mark the locations of visible transits - when a planet passes in front of its parent star.

Dr Lintott points out: "Computerised attempts to find things [in the data] missed this system entirely. That tells you there are probably more of these that are slipping through our fingers. We've just stuck a load of new data up on Planethunters.org to help people find the next one."

Searching for such systems, he said, was "a complicated test to hand a computer", adding: "We're using human pattern recognition, which can disentangle that reasonably well to see the important stuff."

Since December 2010, more than 170,000 members of the public have participated in the project.

http://www.bbc.co.uk/news/science-environment-19950923
 
This isn't Proxima Centauri, but rather Alpha Centauri B, which is a little further away. When Proxima is given a letter it is known as Alpha Centauri C.

The sunward side of the planet is at 1500 K, which is above the melting point of many rocks. Here's my image of the planet as I currently envisage it;
http://www.orionsarm.com/im_store/ixion.jpg

... the bright sunlight on the (permanent) day side would probably drown out the weak glow from the lava, so the planet would look quite a bit different to the naked eye unless you use some sort of special filter.
 
They're looking for a name for this new exoplanet.
I suggest Everday or Nevernight.
 
There's just a tiny chance that the dark side holds some water ice and other volatiles, if it is cold enough; the planet would be mostly inhospitable, but could support a colony using the abundant energy of the sunward side to create air from the local resources. In certain locations on this planet a habitat environment could be surprisingly easy to maintain indefinitely.
 
eburacum said:
There's just a tiny chance that the dark side holds some water ice and other volatiles, if it is cold enough; the planet would be mostly inhospitable, but could support a colony using the abundant energy of the sunward side to create air from the local resources. In certain locations on this planet a habitat environment could be surprisingly easy to maintain indefinitely.
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Is it tidally locked, with no rotation?
How do they know?
 
Mythopoeika said:
Is it tidally locked, with no rotation?
How do they know?
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Because it only has a 3 day orbital period, meaning it's very close in to the star. Tidal braking would thus happen over a very short time span.
 
That's right. Alpha Centauri is old enough that the planet must be tidally locked, assuming the details we have been told so far are correct.

Here's another image, showing the relative sizes of the local sun as seen from Earth, Mercury and Alpha Centauri Bb.
http://www.orionsarm.com/im_store/tolimanb.jpg

This is a very hot world, baked dry of its volatiles. My earlier scenario of an ice-cap on the dark side is looking quite unlikely, according to most experts. However this planet is not quite hot enough to have a thick atmosphere of silicon dioxide; it probably has a very thin atmosphere of gaseous sulphur and some other inhospitable stuff.
 

'Super-Earth' Alien Planet May Be Habitable for Life

'Super-Earth' Alien Planet May Be Habitable for Life

SPACE.com

By Mike Wall | SPACE.com – 9 hours ago


This artist’s impression shows the newfoun potentially habitable alien planet HD40307g in the foreground, with its host star and two other worlds in the six-planet system also depicted. The atmosphere and continents shown are neither detected nView Photo

This artist’s impression shows the newfoun potentially habitable alien planet HD40307g …

Astronomers have detected an alien planet that may be capable of supporting life as we know it — and it's just a stone's throw from Earth in the cosmic scheme of things.

The newfound exoplanet, a so-called "super-Earth" called HD 40307g, is located inside its host star's habitable zone, a just-right range of distances where liquid water may exist on a world's surface. And the planet lies a mere 42 light-years away from Earth, meaning that future telescopes might be able to image it directly, researchers said.

"The longer orbit of the new planet means that its climate and atmosphere may be just right to support life," study co-author Hugh Jones, of the University of Hertfordshire in England, said in a statement. "Just as Goldilocks liked her porridge to be neither too hot nor too cold but just right, this planet or indeed any moons that it has lie in an orbit comparable to Earth, increasing the probability of it being habitable."

HD 40307g is one of three newly discovered worlds around the parent star, which was already known to host three planets. The finds thus boost the star's total planetary population to six. [Video: Super Earth May Have Liquid Water]

Finding new signals in the data

The star HD 40307 is slightly smaller and less luminous than our own sun. Astronomers had previously detected three super-Earths — planets a bit more massive than our own — around the star, all of them in orbits too close-in to support liquid water.

In the new study, the research team re-analyzed observations of the HD 40307 system made by an instrument called the High Accuracy Radial velocity Planet Searcher, or HARPS.

HARPS is part of the European Southern Observatory's 11.8-foot (3.6 meters) telescope at the La Silla Observatory in Chile. The instrument allows astronomers to pick up the tiny gravitational wobbles an orbiting planet induces in its parent star.

The researchers' new analysis techniques enabled them to spot three more super-Earths around the star, including HD 40307g, which is thought to be at least seven times as massive as our home planet.

HD 40307g may or may not be a rocky planet like Earth, said study lead author Mikko Tuomi, also of the University of Hertfordshire.

"If I had to guess, I would say 50-50," Tuomi told SPACE.com via email. "But the truth at the moment is that we simply do not know whether the planet is a large Earth or a small, warm Neptune without a solid surface."

A jam-packed extrasolar system

HD 40307g is the outermost of the system's six planets, orbiting at an average distance of 56 million miles (90 million kilometers) from the star. (For comparison, Earth zips around the sun from about 93 million miles, or 150 million km, away.)

The other two newfound exoplanets are probably too hot to support life as we know it, researchers said. But HD 40307g — which officially remains a "planet candidate" pending confirmation by follow-up studies — sits comfortably in the middle of the star's habitable zone.

Further, HD 40307g's orbit is distant enough that the planet likely isn't tidally locked to the star like the moon is to Earth, researchers said. Rather, HD 40307g probably rotates freely just like our planet does, showing each side of itself to the star in due course.

The lack of tidal locking "increases its chances of actually having Earth-like conditions," Tuomi said.

The new study has been accepted for publication in the journal Astronomy & Astrophysics.

A candidate for direct observation

Super-Earths have been spotted in other stars' habitable zones before. For example, a team using NASA's prolific Kepler Space Telescope announced the discovery of the potentially habitable world Kepler-22b in December 2011.

Kepler-22b lies 600 light-years away, which is not terribly far considering that our Milky Way galaxy is about 100,000 light-years wide. But HD 40307g is just 42 light-years from us — close enough that future instruments may be able to image it directly, scientists say.

"Discoveries like this are really exciting, and such systems will be natural targets for the next generation of large telescopes, both on the ground and in space," David Pinfield of the University of Hertfordshire, who was not involved in the new study, said in a statement.

http://ca.news.yahoo.com/super-earth-al ... 48317.html
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