exoplanets Archives

August 14, 2012December 23, 2015 by Jon Voisey

Two “b”‘s in the Beehive

Praesepe (aka. the Beehive Cluster)

As astronomers near the 800 mark for confirmed extra solar planets, it seems that notable milestones are becoming fewer and further between. Multi-planet systems aren’t even worth mentioning. Planets less massive than Earth? Already heard about it. Detecting atmospheres? Old news.

But a recent paper manages to sneak in one new first: The first detection of hot Jupiters in an open cluster. This discovery is not simply notable due to the novelty, but clusters have special characteristics that can help astronomers determine more of the history of the system.

The discovery was made by astronomers at Georgia State University using the “wobble” method in which they looked for the spectroscopic wiggle of spectral lines as planets tugged their parent stars around in orbit. The Beehive Cluster was chosen because it is a nearby cluster with over 1,000 member stars, many of which are similar in mass to the Sun. Additionally, the cluster is known to have an above average metallicity which is known to be correlated with planetary systems.

Searches of other open clusters have largely come up empty. Only two stars in open clusters have so far been found to have planets and both of those are around giant stars and as such, the planets are in wide orbits. This paucity is odd since stars are expected to form in clusters, and as such, the frequency of planets in clusters should be nearly the same as isolated stars.

The team used the 1.5-m Tillinghast Reflector at the Fred L. Whipple Observatory on Mt. Hopkins, Arizona observing a total of 53 stars in the cluster. Their results uncovered two new hot Jupiter planets in tight orbits around the parent, main-sequence stars. The first has an estimated mass of 0.54 times that of Jupiter while the second weighs in at 1.8 Jupiter masses.

The discovery helps to place constraints on how planets form and migrate in fledgling systems. Since massive planets such as these would need to form further out in colder parts of the circumstellar cloud, such planets would have to move inwards. The time period in which this happens has been a difficult question for astronomers to pin down. But since the Beehive cluster is only 600 million years old and these new planets are already in tight orbits, this helps to demonstrate that such migration is possible on short timescales.

While these are the first of their kind discovered in open clusters, this discovery puts the number of hot Jupiters in open clusters in rough agreement with expectations based on the number of such systems of stars that are no longer bound in clusters. This finding bridges the gap between formation and isolated stars that previous searches of open clusters had left open.

July 20, 2012December 23, 2015 by Jason Major

Exoplanet Gliese 581g Makes the Top 5

Exoplanet Gliese 581g is back, and “officially” ranking #1 on a list of potentially habitable worlds outside of our solar system thanks to new research from the team that originally announced its discovery in 2010.

Orbiting a star 20 light-years away, the super-Earth is now listed alongside other exoplanets Gliese 667Cc, Kepler-22b, HD85512 and Gliese 581d in the University of Puerto Rico at Arecibo’s Habitable Exoplanets Catalog as good places to look for Earthlike environments… and thus the possibility of life.

First announced in September 2010 by a team led by Steven S. Vogt of UC Santa Cruz, the presence of Gliese 581g was immediately challenged by other astronomers whose data didn’t support its existence. Vogt’s team conducted further analysis of the Gliese system in which it appeared that the orbits of the planets were circular, rather than elliptical, and it was in this type of scenario that a strong signal for Gliese 581g once again appeared.

Read: Could Chance For Life on Gliese 581g Actually Be “100%”?

“This signal has a False Alarm Probability of < 4% and is consistent with a planet of minimum mass 2.2M [Earth masses], orbiting squarely in the star’s Habitable Zone at 0.13 AU, where liquid water on planetary surfaces is a distinct possibility” said Vogt.

And, located near the center of its star’s habitable “Goldilocks” zone and receiving about the same relative amount of light as Earth does, Gliese 581 g isn’t just on the list… it’s now considered the best candidate for being an Earthlike world — knocking previous favorite Gliese 667Cc into second place.

Read: Billions of Habitable Worlds Likely in the Milky Way

The announcement was made on the PHL’s press site earlier today by Professor Abel Méndez, Director of the PHL at UPR Arecibo.

Diagram of the Gliese system. The green area is the habitable zone, where liquid water can exist on a planet’s surface. (PHL @ UPR Arecibo)

“The controversy around Gliese 581g will continue and we decided to include it to our main catalog based on the new significant evidence presented, and until more is known about the architecture of this interesting stellar system”

– Prof. Abel Méndez, UPR Arecibo

July 10, 2012December 23, 2015 by John Williams

Sifting Starlight, Finding New Worlds

These two images show HD 157728, a nearby star 1.5 times larger than the sun. The star is centered in both images, and its light has been mostly removed by an adaptive optics system and coronagraph belonging to Project 1640, which uses new technology on the Palomar Observatory’s 200-inch Hale telescope near San Diego, Calif., to spot planets. Credit: Project 1640

Looking directly at stars is a bad way to find planets orbiting faraway suns but using a new technique, scientists can now sift the starlight to find new exoplanets millions of times dimmer than their parent stars.

“We are blinded by this starlight,” says Ben R. Oppenheimer, a curator in the American Museum of Natural History’s Department of Astrophysics and principal investigator for Project 1640. “Once we can actually see these exoplanets, we can determine the colors they emit, the chemical compositions of their atmospheres, and even the physical characteristics of their surfaces. Ultimately, direct measurements, when conducted from space, can be used to better understand the origin of Earth and to look for signs of life in other worlds.”

Using indirect detection methods, astronomers have found hundreds of planets orbiting other stars. The light stars emit, however, is tens of millions to billions of times brighter than the light reflected by planets.

Project 1640 is an advanced telescope imaging system, made up of the world’s most advanced adaptive optics system, instruments and software. The project operates at the 200-inch Hale Telescope at California’s Palomar Observatory. Engineers at the American Museum of Natural History, California Institute of Technology, and NASA’s Jet Propulsion Laboratory worked more than six years developing the new system.

Earth’s atmosphere wreaks havoc with starlight. The heating and cooling of the atmosphere produces turbulence that creates a twinkling effect on the point-like light from a star. Optics within a telescope also warp light. The instruments that make up Project 1640 manipulate starlight by deforming a mirror more than 7 million times a second to counteract the twinkling. This produces a crystal clear infrared image of the star with a precision smaller than one nanometer; about 100 times smaller than a typical bacteria.

“Imaging planets directly is supremely challenging,” said Charles Beichman, executive director of the NASA ExoPlanet Science Institute at the California Institute of Technology. “Imagine trying to see a firefly whirling around a searchlight more than a thousand miles away.”

A coronagraph, built by the American Museum of Natural History, optically dims the star leaving other celestial objects in the field of view. Other instruments help create an “artificial eclipse” inside Project 1640. Only about half a percent of the original light remains in the form of a speckled background. These speckles can still be hundreds of times brighter than the dim planets. The instruments control the light from the speckles to further dim their brightness. What the instrument creates is a dark hole where the star had been while leaving the light reflected from any planets. Coordination of the system is extremely important, say the researchers. Even the smallest light leak would drown out the incredibly faint light from planets orbiting a star.

For now Project 1640, the world’s most advanced and highest contrast imaging system, is focusing on bright stars relatively close to Earth; about 200 light-years away. Their three-year survey includes plans to image hundreds of young stars. The planets they may find are likely to be very large, Jupiter-sized bodies.

“The more we learn about them, the more we realize how vastly different planetary systems can be from our own,” said Jet Propulsion Laboratory astronomer Gautam Vasisht. “All indications point to a tremendous diversity of planetary systems, far beyond what was imagined just 10 years ago. We are on the verge of an incredibly rich new field.”

Read more about Project 1640: http://research.amnh.org/astrophysics/research/project1640

Image Caption: Two images of HD 157728, a nearby star 1.5 times larger than the Sun. The star is centered in both images, and its light has been mostly removed by the adaptive optics system and coronagraph. The remaining starlight leaves a speckled background against which fainter objects cannot be seen. On the left, the image was made without the ultra-precise starlight control that Project 1640 is capable of. On the right, the wavefront sensor was active, and a darker square hole formed in the residual starlight, allowing objects up to 10 million times fainter than the star to be seen. Images were taken on June 14, 2012 with Project 1640 on the Palomar Observatory’s 200-inch Hale telescope. (Courtesy of Project 1640)

July 5, 2012December 23, 2015 by Jason Major

The Case of the Disappearing Dust

Astronomy has always taught us that planets form from vast clouds of dust and gas orbiting young stars. It’s a gradual process of accretion that takes hundreds of thousands, perhaps even millions, of years… or does it?

During a 1983 sky survey with the Infrared Astronomical Satellite (IRAS) astronomers identified a young Sun-like star with a large cloud of dust surrounding it. The star, named TYC 8241 2652 1, is 450 light years away and what they had found around it was thought to be the beginnings of a solar system – the protoplanetary disc from which planets form.

Fast forward to 2008. Astronomers observed at the same star with a different infrared telescope, the Gemini South Observatory in Chile. What was observed looked a lot like what was previously seen in ’83.

Then, in 2009, they looked again. Curiously, the brightness of the dust cloud was only a third of what it was the year before. And in WISE observations made the very next year, it had disappeared entirely.

“It’s like the classic magician’s trick: now you see it, now you don’t. Only in this case we’re talking about enough dust to fill an inner solar system, and it really is gone.”

– Carl Melis, lead author and postdoctoral fellow at UC San Diego

Abracadabra?

“It’s as if you took a conventional picture of the planet Saturn today and then came back two years later and found that its rings had disappeared,” said study co-author and circumstellar disk expert Ben Zuckerman of UCLA.

It’s always been thought that planets take some time to form, in the order of hundreds of thousands of years. Although that may seem like forever to humans, it’s quick in cosmic time scales. But if what they’ve seen here with TYC 8241 is in fact planetary formation, well… it may happen a lot faster than anyone thought.

On the other hand, the star could have somehow blown all the dust out of the system. More research will be needed to see if that was the case.

The really interesting thing here is that astronomers have traditionally looked for these kinds of dust clouds around stars to spot planetary formation in action. But if planets form quicker than we thought, and the dust clouds are only fleeting features, then there may be a lot more solar systems out there that we can’t directly observe.

“People often calculate the percentage of stars that have a large amount of dust to get a reasonable estimate of the percentage of stars with planetary systems, but if the dust avalanche model is correct, we cannot do that anymore,” said study co-author Inseok Song, assistant professor of physics and astronomy at the University of Georgia. “Many stars without any detectable dust may have mature planetary systems that are simply undetectable.”

Top image: Gemini Observatory/AURA artwork by Lynette Cook.

June 27, 2012December 23, 2015 by Jason Major

How to Measure a Hot Jupiter

An international team of astronomers has figured out a way to determine details of an exoplanet’s atmosphere from 50 light-years away… even though the planet doesn’t transit the face of its star as seen from Earth.

Tau Boötis b is a “hot Jupiter” type of exoplanet, 6 times more massive than Jupiter. It was the first planet to be identified orbiting its parent star, Tau Boötis, located 50 light-years away. It’s also one of the first exoplanets we’ve known about, discovered in 1996 via the radial velocity method — that is, Tau Boötis b exerts a slight tug on its star, shifting its position enough to be detectable from Earth. But the exoplanet doesn’t pass in front of its star like some others do, which until now made measurements of its atmosphere impossible.

Today, an international team of scientists working with the Very Large Telescope (VLT) at ESO’s Paranal Observatory in Chile have announced the success of a “clever new trick” of examining such non-transiting exoplanet atmospheres. By gathering high-quality infrared observations of the Tau Boötis system with the VLT’s CRIRES instrument the researchers were able to differentiate the radiation coming from the planet versus that emitted by its star, allowing the velocity and mass of Tau Boötis b to be determined.

“Thanks to the high quality observations provided by the VLT and CRIRES we were able to study the spectrum of the system in much more detail than has been possible before,” said Ignas Snellen with Leiden Observatory in the Netherlands, co-author of the research paper. “Only about 0.01% of the light we see comes from the planet, and the rest from the star, so this was not easy.”

Using this technique, the researchers determined that Tau Boötis b’s thick atmosphere contains carbon monoxide and, curiously, exhibits cooler temperatures at higher altitudes — the opposite of what’s been found on other hot Jupiter exoplanets.

“Maybe one day we may even find evidence for biological activity on Earth-like planets in this way.”

– Ignas Snellen, Leiden Observatory, the Netherlands

In addition to atmospheric details, the team was also able to use the new method to determine Tau Boötis b’s mass and orbital angle — 44 degrees, another detail not previously identifiable.

“The new technique also means that we can now study the atmospheres of exoplanets that don’t transit their stars, as well as measuring their masses accurately, which was impossible before,” said Snellen. “This is a big step forward.

“Maybe one day we may even find evidence for biological activity on Earth-like planets in this way.”

This research was presented in a paper “The signature of orbital motion from the dayside of the planet Tau Boötis b”, to appear in the journal Nature on June 28, 2012.

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

May 18, 2012December 23, 2015 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

May 17, 2012December 23, 2015 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

May 10, 2012December 23, 2015 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.

May 9, 2012December 23, 2015 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-Golden-Record — 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.