Posted on by Nancy Atkinson

What a View! Exoplanet Odd Couple Orbit in Close Proximity

Imagine if the Neptune was only a million miles from Earth. What a view we’d have! … not to mention some incredible gravitational effects from the close-by, gigantic planet. A similar scenario is taking place for real in star system in the constellation Cygnus. A newly found planet duo orbiting a sun-like star come together in extremely close proximity, and strangely enough, the two planets are about as opposite as can be: one is a rocky planet 1.5 times the size of Earth and weighs 4.5 times as much, and the other is a gaseous planet 3.7 times the size of Earth and weighing 8 times that of Earth.

“They are the closest to each other of any planetary system we’ve found,” said Eric Agol of the University of Washington, co-author of a new paper outlining the discovery of this interesting star system by the Kepler spacecraft. “The bigger planet is pushing the smaller planet around more, so the smaller planet was harder to find.”

Known as Kepler-36, the star is a several billion years older than our Sun, and at this time is known to have just two planets.

The inner rocky world, Kepler-36b orbits about every 14 days at an average distance of less than 11 million miles, while the outer gas “hot Neptune” planet orbits once each 16 days at a distance of 12 million miles.

The two planets experience a conjunction every 97 days on average. At that time, they are separated by less than 5 Earth-Moon distances. Since Kepler-36c is much larger than the Moon, it presents a spectacular view in its neighbor’s sky. And the science team noted that the smaller Kepler-36b would appear about the size of the Moon when viewed from Kepler-36c).

But the timing of their orbits means they’ll never collide, Agol said. However, close encounters of this kind would cause tremendous gravitational tides that squeeze and stretch both planets.

The larger planet was originally spotted in data from NASA’s Kepler spacecraft, which uses a photometer to measure light from distant celestial objects and can detect a planet when it transits, or passes in front of, and briefly reduces the light coming from, its parent star.

The team wanted to try finding a second planet in a system where it was already known that there was one planet. Agol suggested applying an algorithm called quasi-periodic pulse detection to examine data from Kepler.

The data revealed a slight dimming of light coming from Kepler-36a every 16 days, the length of time it takes the larger Kepler-36c to circle its star. Kepler-36b circles the star seven times for each six orbits of 36c, but it was not discovered initially because of its small size and the gravitational jostling by its orbital companion. But when the algorithm was applied to the data, the signal was unmistakable.

“If you look at the transit time pattern for the large planet and the transit time pattern for the smaller planet, they are mirror images of one another,” Agol said.

The fact that the two planets are so close to each other and exhibit specific orbital patterns allowed the scientists to make fairly precise estimates of each planet’s characteristics, based on their gravitational effects on each other and the resulting variations in the orbits. To date, this is the best-characterized system with small planets, the researchers said.

From their calculations, the team estimates the smaller planet is 30 percent iron, less than 1 percent atmospheric hydrogen and helium and probably no more than 15 percent water. The larger planet, on the other hand, likely has a rocky core surrounded by a substantial amount of atmospheric hydrogen and helium.

The planets’ densities differ by a factor of eight but their orbits differ by only 10 percent. The big differences in composition and the close proximity of the two is quite a head-scratcher, as current models of planet formation don’t really predict this. But the team is wondering if there are more systems like this out there.

“We found this one on a first quick look,” said co-author Josh Carter, a Hubble Fellow at the Harvard-Smithsonian Center for Astrophysics (CfA). “We’re now combing through the Kepler data to try to locate more.”

Lead image caption: This image, adapted by Eric Agol of the UW, depicts the view one might have of a rising Kepler-36c (represented by a NASA image of Neptune) if Seattle (shown in a skyline photograph by Frank Melchior, frankacaba.com) were placed on the surface of Kepler-36b.

Second image caption: In this artist’s conception, a “hot Neptune” known as Kepler-36c looms in the sky of its neighbor, the rocky world Kepler-36b. The two planets have repeated close encounters, experiencing a conjunction every 97 days on average. At that time, they are separated by less than 5 Earth-Moon distances. Such close approaches stir up tremendous gravitational tides that squeeze and stretch both planets, which may promote active volcanism on Kepler-36b.
Credit: David A. Aguilar (CfA)

Sources: CfA, University of Washington

Posted on by Andy Tomaswick

Terrestrial Planets Could be More Common Than Gas Giants

This artist's conception shows a newly formed star surrounded by a swirling protoplanetary disk of dust and gas. Credit: University of Copenhagen/Lars Buchhave

Editor’s note: This guest post was written by Andy Tomaswick, an electrical engineer who follows space science and technology.

As acclaimed astronomer Carl Sagan once famously noted, “We are all made of star-stuff.” So are the multitudes of extra-solar planets that are currently being discovered at a breathtaking pace. What Sagan meant was that all of the elements heavier than hydrogen and helium, commonly known as “metals” to astrophysicists, must be created in the interior furnaces of stars. But it takes time for stars to create these heavier elements, and since they are needed to start planets those time spans could have a major impact on solar system formation.

New research led by the University of Copenhagen with help from the Harvard-Smithsonian Center for Astrophysics sheds some light on those time spans. In a paper recently presented at a meeting of the American Astronomical Society, Lars Buchhave and his team selected more than 150 stars with known planetary systems that were cataloged by NASA’s Kepler mission. They then studied these star’s metal content and the size of the planets in their solar systems. What they found was that gas giant planets were more likely to form around metal rich stars, whereas terrestrial planets were equally likely to form around metal rich or metal poor stars.

As the team explains, the reason for this fits neatly into the “core accretion” model of planetary formation. Each gas giant has a metal core which hydrogen and helium accumulate around. However, if there is no core to collect around, the lighter elements will be blown away by stellar winds while the star is still relatively young. If a star has a high enough metal content, its potential planets might be able to form a large metallic core quickly, before the winds do their work. The core will then gravitationally attract the remaining gas to itself and a new gas giant is born.

On the other hand, the formation of terrestrial planets is not dependent on helium and hydrogen and therefore not subject to the same time constraints. If a star has lower metal content it might take longer to form terrestrial planets, but all the ingredients are still there. Essentially, there is no upper time limit for a terrestrial planet to form whereas a gas giant must develop quickly to keep its hydrogen and helium trapped within the solar system.

Like all good research, these results open up many more questions. How quickly must a gas giant’s core form before its material is lost? Are terrestrial planets much more common given their greater creation timescales and more numerous potential parent stars? Future work on extra-solar planetary systems might help to provide more answers.

Lead image caption: This artist’s conception shows a newly formed star surrounded by a swirling protoplanetary disk of dust and gas. Credit: University of Copenhagen/Lars Buchhave

Source: Harvard-Smithsonian Center for Astrophysics

Posted on by Nancy Atkinson

First SETI Search of Gliese 581 Finds No Signs of ET

An artist’s impression of Gliese 581d, an exoplanet about 20.3 light-years away from Earth, in the constellation Libra. Credit: NASA

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The first targeted SETI search of a system with a potentially habitable world has come up empty, but perhaps finding signals wasn’t the main objective in this search. Back in 2007 a group of astronomers used the Australian Long Baseline Array to listen for radio signals from Gliese 581, a red dwarf star that is now known to host at least six planets, with one in the star’s habitable zone. This was a SETI-type search for extraterrestrial-made signals, and it initially found 222 candidate signals. However, the team was able to reject all of them using automated analysis techniques, determining they were caused by Earth orbiting satellites. So why is this potentially good news?

This search was actually a proof of concept for using the Very Long Baseline Interferometry (VLBI) for targeted SETI searches, and that it worked well is great news for future searches that look specifically at a particular star system. Until recently most SETI searches were wide sky surveys, scanning wide, random areas of space looking for radio signals. But now, with the success of the exoplanet hunting Kepler mission, we now know of some potentially habitable systems and planets, and astronomers can do targeted searches, looking at specific spots in the sky.

It wasn’t known if the VLBI technique would be successful for such a “directed” targeted search, but this search by Hayden Rampadarath and team from the International Centre for Radio Astronomy Research at Curtin University in Australia proves it does.

The Australian Long Baseline Array is a combination of three radio antennae: the 22-meter Mopra Telescope, Parkes Observatory and the Australia Telescope Compact Array (ATCA) which are each a few hundred kilometers apart from each other. The data from the three locations are combined, making them act as one huge radio telescope, with an extraordinary angular resolution in the milli-arcsecond regime, the highest resolution in astronomy. And it turns out that VLBI techniques are great for SETI searches because they automatically exclude many Earth-based sources of interference that might otherwise look like SETI signals. That’s because the same signals have to show up at all the telescopes several hundred kilometers apart.

The team pointed the telescopes at Gliese 581 (Gl581), located 20 light-years distant in the constellation Libra for about 8 hours, tuning into frequencies close to 1500 megahertz.

The team said that the array would have been able to pick up a broadcast with a power output of at least 7 megaWatts per hertz, which means that if Gliese inhabitants had been broadcasting directly to Earth using an 300-meter Arecibo-style dish, the signals would have easily been picked up. However, ordinary radio transmissions, such as the ones Earthlings regularly transmit into space, would have been too weak to be detected.

But this bodes well for using other more powerful VLBI arrays such as the European VLBI Network, current most-sensitive VLBI array in the world or the upcoming Square Kilometre Array, which will have the sensitivity to pick up broadcasts of a few kilowatts per Hertz from 20 light years away.

So while this doesn’t mean that there is no life in the Gliese 581 system, this does mean we now have an expanded arsenal of tools for looking.

Read the team’s paper.

Source: Technology Review Blog

Posted on by Jason Major

Worlds Without Suns: Nomad Planets Could Number In The Quadrillions

Artist's concept of a free-floating Jupiter-like planet. (NASA / JPL-Caltech)

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The concept of nomad planets has been featured before here on Universe Today, and for good reason. Not only is the idea of mysterious lone planets drifting sunless through interstellar space an intriguing one, but also the sheer potential quantity of such worlds is simply staggering. If some very well-respected scientists’ calculations are correct there are more nomad planets in our Milky Way galaxy than there are stars — a lot more. With estimates up to 100,000 nomad planets for every star in the galaxy, there could be literally quadrillions of wandering worlds out there, ranging in size from Pluto-sized to even larger than Jupiter.

That’s a lot of nomads. But where did they all come from?

Recently, The Kavli Foundation had a discussion with several scientists involved in nomad planet research. Roger D. Blandford, Director of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University, Dimitar D. Sasselov, Professor of Astronomy at Harvard University and Louis E. Strigari, Research Associate at KIPAC and the SLAC National Accelerator Laboratory talked about their findings and what sort of worlds these nomad planets might be, as well as how they may have formed.

One potential source for nomad planets is forceful ejection from solar systems.

“Most stars form in clusters, and around many stars there are protoplanetary disks of gas and dust in which planets form and then potentially get ejected in various ways,” said Strigari. “If these early-forming solar systems have a large number of planets down to the mass of Pluto, you can imagine that exchanges could be frequent.”

And the possibility of planetary formation outside of stellar disks is not entirely ruled out by the researchers — although they do impose a lower limit to the size of such worlds.

“Theoretical calculations say that probably the lowest-mass nomad planet that can form by that process is something around the mass of Jupiter,” said Strigari. “So we don’t expect that planets smaller than that are going to form independent of a developing solar system.”

“This is the big mystery that surrounds this new paper. How do these smaller nomad planets form?” Sasselov added.

Of course, without a sun of their own to supply heat and energy one might assume such worlds would be cold and inhospitable to life. But, as the researchers point out, that may not always be the case. A nomad planet’s internal heat could supply the necessary energy to fuel the emergence of life… or at least keep it going.

“If you imagine the Earth as it is today becoming a nomad planet… life on Earth is not going to cease,” said Sasselov. “That we know. It’s not even speculation at this point. …scientists already have identified a large number of microbes and even two types of nematodes that survive entirely on the heat that comes from inside the Earth.”

Researcher Roger Blandford also suggested that “small nomad planets could retain very dense, high-pressure ‘blankets’ around them. These could conceivably include molecular hydrogen atmospheres or possibly surface ice that would trap a lot of heat. They might be able to keep water liquid, which would be conducive to creating or sustaining life.”

And so with all these potentially life-sustaining planets knocking about the galaxy,  is it possible that they could have helped transport organisms from one solar system to another? It’s a concept called panspermia, and it’s been around since at least the 5th century BCE when the Greek philosopher Anaxagoras first wrote about it. (We’ve written about it too, as recently as three weeks ago, and it’s still a much-debated topic.)

“In the 20th century, many eminent scientists have entertained the speculation that life propagated either in a directed, random or malicious way throughout the galaxy,” said Blandford. “One thing that I think modern astronomy might add to that is clear evidence that many galaxies collide and spray material out into intergalactic space. So life can propagate between galaxies too, in principle.

There could be quadrillions of nomad planets in our galaxy alone -- and they could even be ejected into intergalactic space. (Image: ESO/S.Brunier)

“And so it’s a very old speculation, but it’s a perfectly reasonable idea and one that is becoming more accessible to scientific investigation.”

Nomad planets may not even be limited to the confines of the Milky Way. Given enough of a push, they could be sent out of the galaxy entirely.

“Just a stellar or black hole encounter within the galaxy can, in principle, give a planet the escape velocity it needs to be ejected from the galaxy. If you look at galaxies at large, collisions between them leads a lot of material being cast out into intergalactic space,” Blandford said.

The discussion is a fascinating one and can be found in its entirety on The Kavli Foundation’s site here, and watch a recorded interview between Louis Strigari and journalist Bruce Lieberman here.

The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

Posted on by Jon Voisey

A Planetary System That Never Was Teaches About Those That May Be

While Kepler and similar missions are turning up planets by the fist full, there’s long been many places that astronomers haven’t expected to find planetary systems. The main places include regions where gravitational forces conspire to make the region around potential host stars too unstable to form into planets. And there’s no place in the galaxy with a larger gravitational force than the galactic center where a black hole four and a half million times more massive than the Sun, lurks. But a new study shows evidence that a disk, potentially far enough along to begin forming planets, is in the process of being disrupted.

The new study investigates an ionized cloud of gas discovered earlier this year, plummeting in towards the black hole. The cloud has been formed into an elliptical ring with a maximum distance of 0.04 parsecs (1 parsec 3.24 light years) which is coincident with a ring of young stars that orbit the black hole. At such distances from us, astronomers have been unable to learn much about the population of stars that may exist since only the brightest, most massive stars are visible.

However, such massive stars are able to determine an age limit for the group, which has been set somewhere between 4-8 million years. This age is crucial since most low-mass stars retain gas disks and are held to form planets at an age around 3 million years young. But by an age of 5 million years, the stars have begun clearing out that disk system halting planetary formation and only one fifth of stars less than 1 solar mass retain their disks.

This entire process is even more precarious because the gravitational perturbations from the nearby black hole would begin eating away at the edge of a potential disk. Astronomers predict that this should limit the size to 12 AU in radius. For even less massive stars, this could be as small as 8 AU. Still, theory predicts that these truncated disks could form in the vicinity of the Milky Way’s black hole. But such small disks would be impossible to observe directly with present technology.

The new research suggests that one of these stars was knocked from its stable orbit in the ring in much the same way that comets in the Oort cloud are occasionally jostled into falling towards the inner solar system. There, the tidal forces from the black hole as well as heavily ionizing UV radiation created by the black hole’s accretion disk would strip the gas and dust from the parent star, which is too faint to see directly, leaving it in an elliptical orbit.

If this theory is correct, it would provide the first indirect evidence of the presence of planet forming disks near the galactic center. This comes on top of evidence from earlier this year suggesting stars may be able to form in situ near the galactic center making this region a far more dynamic place than previously expected.

Yet, even if planets do form, living near a supermassive black hole is still not a hospitable place for life. The extreme amounts of UV radiation emitted as the black hole devours gas and dust is likely to sterilize the region.

Posted on by Nancy Atkinson

Doomed Mercury-Sized Exoplanet May Be Turning to Dust

Artist concept of the curious events going at the star named KIC 12557548. Credit: MIT

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The old saying of the universe being stranger than we can imagine definitely applies to a newfound exoplanet orbiting a star about 1,500 light years from Earth. Researchers using the Kepler space observatory have detected what appears to be a planet about the size of Mercury literally turning to dust. A long tail of debris — almost like a comet’s tail — is following the planet as it whirls around the star, KIC 12557548. Scientists think the planet could be evaporating under the blistering heat of the star, and that by analyzing the dust, they could decipher the history of the planet. But they better hurry. According to the team’s calculations, the planet will completely disintegrate within 100 million years.

“This might be another way in which planets are eventually doomed,” said Dan Fabrycky, a member of the Kepler Observatory science team.

Besides finding such an unusual planet, this is another leap forward for teams using Kepler data, being able to detect such a small planet orbiting so close to its parent star. The orbital period is 15 hours — one of the shortest planet orbits ever observed. The research team initially saw strange patterns of light from the star, and in examining the star’s light curves, they found the light dropped by different intensities every 15 hours — suggesting that something was blocking the star regularly, but by varying degrees.

The team considered that there might be a planetary duo — two planets orbiting each other — where their orbits would block out different amounts of light during each eclipse, but the data failed to support this hypothesis.

Instead, the researchers came up with a novel hypothesis: that the varying intensities of light were caused by a somewhat amorphous, shape-shifting body.

In looking at the short orbit, they realized the planet must be heated by its orange-hot parent star to a temperature of about 1,982 degrees Celsius (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.

“It had to be something that was fundamentally changing,” said co-author Saul Rappaport, a professor emeritus of physics at MIT. “It was not a solid body, but rather, dust coming off the planet. We think this dust is made up of submicron-sized particles.”

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 eventually completely disintegrate.

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.”

“A lot of research has come to the conclusion that planets are not eternal objects,” said Fabrycky. “They can die extraordinary deaths, and this might be a case where the planet might evaporate entirely in the future.”

The group’s findings were published in the Astrophysical Journal.

Source: MIT

Posted on by Jason Major

JPL Wants To FINESSE Info From Exoplanets

FINESSE would observe exoplanets from a position in low-Earth orbit (NASA/JPL-Caltech)


Jet Propulsion Laboratory’s proposed FINESSE space telescope may not hunt for exoplanets, but it will find out what they’re made of.

Part of NASA’s Explorers program, FINESSE — which stands for (take a deep breath) Fast INfrared Exoplanet Spectroscopy Survey Explorer — would gather spectroscopic data from 200 known exoplanets over a two-year period, helping scientists to determine the composition of their atmospheres, surfaces, and even their weather.

While huge discoveries have been made by both ground- and space-based telescopes like Kepler and Corot over the past several years, identifying thousands of exoplanetary candidates, FINESSE will be the first mission dedicated to finding out what the atmospheres are like on worlds outside our solar system.

Using a sensitive spectrograph covering 0.7-5.0 microns, FINESSE will be able to identify molecular bands of water, methane, carbon monoxide, carbon dioxide, and other molecules. Its sensitivity and stability will even allow it to detect the differences between an exoplanet’s day and night side, allowing wind flow and weather to be determined.

Known as an Offner spectrometer, the design of the FINESSE detector is derived from the Moon Mineralogy Mapper instrument, which was designed at JPL and flew to the Moon aboard India’s Chandrayaan-1 spacecraft.

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Touted as “the next step” in exoplanetary exploration, FINESSE is proposed for launch in October 2016.

Learn more at JPL’s FINESSE site here.

“FINESSE is the next step in humankind’s journey of understanding our place in the cosmos.”

– Mark Swain, principal investigator for FINESSE

Posted on by Jason Major

Rogue Planets Could Drive By And Scoop Up Life

Artist's rendering of an Earth-sized rogue planet approaching a star. Credit: Christine Pulliam (CfA)

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Free-floating “rogue” planets may occasionally dip into the inner Solar System, picking up dust containing organic compounds — a.k.a. the ingredients for life — and carry it back out into the galaxy, according to new research by Professor Chandra Wickramasinghe, Director of the University of Buckingham Centre for Astrobiology in the UK.

Rogue planets are thus called because they are not in orbit around a star. Either forcibly ejected from a solar system or having formed very early on in the Universe — even within a few million years after the Big Bang, the team proposes — these vagrant worlds may vastly outnumber stars. In fact, it’s been suggested there are as much as 100,000 times more rogue planets than stars in our Milky Way galaxy alone!

Read: Rogue Planets Can Find Homes Around Other Stars

Professor Wickramasinghe — a proponent of the panspermia hypothesis whereby the ingredients for life can be transported throughout the galaxy on dust, comets, and perhaps even planets — and his team have suggested in a paper published in the journal Astrophysics and Space Science that Earth-sized rogue planets could pass through the inner Solar System, possibly as often as once every 25 million years on average. Like a cosmic drive-thru these planets could gather zodiacal dust from the plane of the Solar System during their pass, thus picking up organic compounds along the way.

The planets would then take the material gathered from one solar system and possibly bring it into another, serving as a type of interstellar cross-pollinator.

Wickramasinghe’s team propose that, by this process, there could be more life-bearing, Earth-sized planets existing between the stars than orbiting around them — a lot more. Based on their estimates there may be as much as a few hundred thousand billion such worlds in our galaxy… that’s several thousand for every star.

It will be interesting to see how this idea is received, but it definitely is an intriguing concept. As we hunt for the “Holy Grail” of life-friendly exoplanets around other stars, they may be drifting through the darkness in number, hiding in the spaces between.

Posted on by Jason Major

Alien Life May Not Be So Alien – If It Exists At All

Our galaxy has exoplanets, organic compounds, liquid water -- even a nebula shaped like a DNA helix -- but is there life? (Image credit: M. Morris/UCLA)

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Are we too hopeful in our hunt for extraterrestrial life? Regardless of exoplanet counts, super-Earths and Goldilocks zones, the probability of life elsewhere in the Universe is still a moot point — to date, we still only know of one instance of it. But even if life does exist somehow, somewhere besides Earth, would it really be all that alien?

In a recent paper titled “Bit by Bit: the Darwinian Basis for Life” Gerald Joyce, Professor of Molecular Biology and Biochemistry at the Scripps Research Institute in La Jolla, CA discusses the nature of life as we know it in regards to its fundamental chemical building blocks — DNA, RNA — and how its ability to pass on the memory of its construction separates true biology from mere chemistry.

“Evolution is nothing more than chemistry plus history,” Joyce said during a Public Library of Science podcast.

The DNA structures that evolved here on Earth — the only place in the Universe we know for certain that life can thrive — have proven to be highly successful (obviously). So what’s to say that life elsewhere wouldn’t be based on the same basic building blocks? And if it is, is it really a “new” life form?

“Truly new ‘alternative life’ would be life of a different biology,” Joyce said. “It would not have the information in it that is part of the same heritage of our life form.”

To arise in the first place, according to Joyce, new life can take two possible routes. Either it begins as chemical connections that grow increasingly more complex until they begin to hold on to the memory of their specific “bit” structure, eventually “bit-flipping” — aka, mutating — into new structures that are either successful or unsuccessful, or it starts from a more “privileged” beginning as an offshoot of previous life, bringing bits into a totally new, immediately successful orientation.

With those two scenarios, anywhere besides Earth “there are no example of either of those conditions so far.”

That’s not saying that there’s no life elsewhere in the Universe… just that we have yet to identify any evidence of it. And without evidence, any discussion of its probability is still pure conjecture.

“In order to estimate probabilities, we need facts,” said Joyce. “The problem is, there is only one life form. And so it’s not possible to estimate probability of life elsewhere when you have only one example.”

Voyager included a golden record with images and sounds of Earthly life recorded on it... just in case. (NASA)

Even though exoplanets are being found on a nearly daily basis, and it’s only a matter of time before a rocky, Earthlike world with liquid water on its surface is confirmed orbiting another star, that’s no guarantee of the presence of alien life — despite what conclusions the headlines will surely jump to.

There could be a billion habitable planets in our galaxy. But what’s the relationship between habitable and inhabited?” Joyce asks. “We don’t know.”

Still, we will continue to search for life beyond our planet, be it truly alien in nature… or something slightly more familiar. Why?

“I think humans are lonely,” Joyce said. “I think humans are like Geppetto — we want to have a ‘real boy’ out there that we can point to, we want to find a Pinocchio living on some extrasolar planet… and then somehow we won’t be such a lonely life form.”

And who knows… if any aliens out there really are a lot like us, they may naturally be searching for evidence of our existence as well. If only to not be so lonely.

Listen to the full PLoS podcast here.

Posted on by Nancy Atkinson

Light From a ‘SuperEarth’ Detected for the First Time

NASA's Spitzer Space Telescope was able to detect a super Earth's direct light for the first time using its sensitive heat-seeking infrared vision. Super Earth's are more massive than Earth but lighter than gas giants like Neptune. As this artist's concept shows, in visible light, a planet is lost in the glare of its star (top view). When viewed in infrared, the planet becomes brighter relative to its star. This is largely due to the fact that the planet's scorching heat blazes with infrared light. Even on our own bodies emanate more infrared light than visible due to our heat. Image credit: NASA/JPL-Caltech

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The star 55 Cancri has been a source of joy and firsts for planet hunters. Not only was it one of the first known stars to host an extrasolar planet, but now the light from one of its five known planets has been detected directly with the Spitzer Space Telescope, the first time a ‘smaller’ exoplanet’s light has been detected directly. Planet “e” is a super-Earth, about twice as big and eight times as massive as Earth. Scientists say that while the planet is not habitable, the detection is a historic step toward the eventual search for signs of life on other planets.

“Spitzer has amazed us yet again,” said Bill Danchi, Spitzer program scientist. “The spacecraft is pioneering the study of atmospheres of distant planets and paving the way for NASA’s upcoming James Webb Space Telescope to apply a similar technique on potentially habitable planets.”


The first planet around 55 Cancri was reported in 1997 and 55 Cancri e – the innermost planet in the system — was discovered via radial velocity measurements in 2004. This planet has been studied as much as possible, and astronomers were able to determine its mass and radius.

But now, Spitzer has measured how much infrared light comes from the planet itself. The results reveal the planet is likely dark, and its sun-facing side is more than 2,000 Kelvin (1,726 degrees Celsius, 3,140 degrees Fahrenheit), hot enough to melt metal.

In 2005, Spitzer became the first telescope to detect light from a planet beyond our solar system, when it saw the infrared light of a “hot Jupiter,” a gaseous planet much larger than 55 Cancri e. Since then, other telescopes, including NASA’s Hubble and Kepler space telescopes, have performed similar feats with gas giants using the same method.

In this method, a telescope gazes at a star as a planet circles behind it. When the planet disappears from view, the light from the star system dips ever so slightly, but enough that astronomers can determine how much light came from the planet itself. This information reveals the temperature of a planet, and, in some cases, its atmospheric components. Most other current planet-hunting methods obtain indirect measurements of a planet by observing its effects on the star.

The new information about 55 Cancri e, along with knowing it is about 8.57 Earth masses, the radius is 1.63 times that of Earth, and the density is 10.9 ± 3.1 g cm-3 (the average density of Earth is 5.515 g cm-3), places the planet firmly into the categories of a rocky super-Earth. But it could be surrounded by a layer of water in a “supercritical” state where it is both liquid and gas, and topped by a blanket of steam.

“It could be very similar to Neptune, if you pulled Neptune in toward our sun and watched its atmosphere boil away,” said Michaël Gillon of Université de Liège in Belgium, principal investigator of the research, which appears in the Astrophysical Journal. The lead author is Brice-Olivier Demory of the Massachusetts Institute of Technology in Cambridge.

The 55 Cancri system is relatively close to Earth, at 41 light-years away, and the star can be seen with the naked eye. 55 Cancri e is tidally locked, so one side always faces the star. Spitzer discovered the sun-facing side is extremely hot, indicating the planet probably does not have a substantial atmosphere to carry the sun’s heat to the unlit side.

NASA’s James Webb Space Telescope, scheduled to launch in 2018, likely will be able to learn even more about the planet’s composition. The telescope might be able to use a similar infrared method to Spitzer to search other potentially habitable planets for signs of molecules possibly related to life.

“When we conceived of Spitzer more than 40 years ago, exoplanets hadn’t even been discovered,” said Michael Werner, Spitzer project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Because Spitzer was built very well, it’s been able to adapt to this new field and make historic advances such as this.”

During Spitzer’s ongoing extended mission, steps were taken to enhance its unique ability to see exoplanets, including 55 Cancri e. Those steps, which included changing the cycling of a heater and using an instrument in a new way, led to improvements in how precisely the telescope points at targets.

Source: JPL