Retro Exo and Its Originators

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David Delgado, visual Strategist for NASA's Jet Propulsion Lab, co-designed the Orbital Pavillion sculpture for the World Science Festival in New York. (Ramsay de Give, The Wall Street Journal)
David Delgado, visual Strategist for NASA’s Jet Propulsion Lab, co-designed the Orbital Pavilion sculpture for the World Science Festival in New York. (Ramsay de Give, The Wall Street Journal)

Exoplanets are mysterious, they’re complicated, they’re important, they’re awe-inspiring.   And, to a team of artists at the Jet Propulsion Lab, they’re also totally fun.

They’re a topic for endless artistic creation because they’re that remarkable combination of brand new and, surprisingly, comfortably familiar.  Exoplanets may be weird and wild but they’re also potentially home to life and, well, people.  And what better way to describe and talk about exoplanets than in a context we all understand — as a travel destination where one of us just might some day spend some time.

Thus was born the series of exoplanet posters — created by artists of JPL’s imaginary Exoplanet Travel Bureau — that have caught the imagination of millions.  When the JPL team put highest quality copies of their posters onto their Planet Quest website in summer, the traffic was so great that the site crashed.

Where the sun shines red. (NASA/JPL)
Where the sun shines red.
        (NASA/JPL-Caltech)

We know that JPL is extraordinary when it comes to designing, building and then operating satellites and rovers, but extraordinary in art, too?

“We had this idea — we wanted to say something real about these planets, something based on firm scientific discoveries, but we also wanted it to be approachable and appealing,” said David Delgado, one of the three members of the JPL art team called “The Studio” which designed and produced the now iconic posters. He has a background in teaching (at JPL), in graphic communications and, initially, in advertising.

“Each poster would have one planet, and we would illustrate one strange or wonderful aspect of it.  It kind of caught on.”

While the idea of creating some exo-posters had been bouncing around for some time in the minds of three of the members of the JPL art team — Delgado, Joby Harris and Daniel Goods — it was a specific event and specific need that brought them to life.

Last year, MIT exoplanet pioneer Sara Seager was coming to JPL, and the exoplanet office wanted something special to greet her.  So it was a perfect moment to finally execute the exo-poster plan.  Three posters were created, one showing a super-Earth with low gravity, one a planet orbiting a pair of binary stars, and one where the nature of the sun’s radiation might produce vegetation of a different color than on Earth (if any vegetation existed, that is.)

A Tatoonie planet with two suns. (NASA/JPL)
A Tatoonie planet with two suns. (NASA/JPL-Caltech)

“They were supposed to be seen in hallway, just to kind of decorate the area for a welcome,” said Harris, the primary illustrator.  “It was really dark, so we had to figure out lighter colors to use and maybe a different kind of style.”

“Little did we know how it would take off.  People were stopping to look at the posters and figure them out, interns were taking pictures, summer students were flocking in,” he said.  “Pretty soon people were asking for copies and our office said, sure, let’s make copies.”

So those copies were released early this year and, because they are NASA products, they were all free.  News of the posters was soon all over Twitter and Reddit and JPL’s Planet Quest site (http://planetquest.jpl.nasa.gov/exoplanet_travel_bureau) came crashing down.

For first recipient Seager, her hallway introduction to the posters was a delightful “wow” moment:  “In exoplanets, so many things that happen surprise us by exceeding anything we could have imagined. Usually that sentiment is for new exponent discoveries, but in this case its for the how iconic the posters have become, and the public reaction to them.”  She has copies hanging in her home, in her office and uses them in her public talks.

None of the particular planets selected is considered habitable by the experts, but all had a human visitor included nonetheless.  And that’s how the seemingly visceral connection with viewers was made. Looking back, Delgado sees the inclusion of people as essential.

“There were some objections for sure to having people in the posters.  It seemed to be communicating that NASA was going to these places with astronauts, and clearly it is not,” Delgado said.  “But people want to place themselves on these planets, to be a viewer who experiences what it might be like.  As a way to get folks excited about exoplanets and learn, seems fine to me.”

Clearly, the look, the artistry of the posters was a driving force, too  Many illustrations of celestial bodies come with a kind of classic sci-fi imagination that emphasizes drama, collisions, sharp lined realism and bright colors.  The Travel Bureau posters are a polar opposite — retro and at times Art Deco. Some have pointed out that they look a tad like Amtrak’s travel posters or the work of a few artists experimenting in science fiction, but there’s no doubting that their work was novel.

Most fully Art Deco poster of a planet with no sun, created for a science gathering. (NASA/JPL)
Most fully Art Deco poster of a planet with no sun, created for a science gathering. (NASA/JPL-Caltech)

It was illustrator Harris who brought that sensibility to the project.  He has a background in special effects, graphics and film– where he was exposed to the art deco look.  He also works in television; one of his early projects was to design some of the props for what became the cult science fiction series “Firefly.”

The poster’s retro look came from a desire to meld nostalgia and the past with the cutting edge future — a return to travel posters of the 20s and 30s, but with rather different destinations.

“We were aiming for a retro-futuristic look, something that brings science fiction into the everyday present,” Delgado said. “It’s like we’re living in the future, or science fiction is coming to life.”

The look has indeed spawned much competition from private artists, who have created planetary and exoplanetary posters in a similar vein.  Delgado thinks that many are just fine, but a little limited.  “Everyone loves the look.  But some capture the fun without the truth of the science.”

Poster for the 20th anniversary celebration in Washington of the discovery of earliest exoplanets. (NASA/JPL)
Poster for the 20th anniversary celebration in Washington of the discovery of earliest exoplanets. (NASA/JPL-Caltech)

“Visual Strategist” Daniel Goods was the artistic director for the project, and he was the one who came up with the idea of adding a line of text highlighting the science.  Goods, like the others, has also created substantial art and sculpture installations around the JPL campus, some of which tour the nation and the world and have won awards. The posters, for instance, are now on display at a major art exhibition in Stockholm.

Goods is a native of Alaska with little science background, who grew up in Oregon and Seattle somehow now shines in L.A.  He and the others say they thrive on asking questions of the scientists and integrating their knowledge into “The Studio’s” work.

The posters took particular outreach and study to get the right scientific message:

“Where Your Shadow Always has Company” for a planet orbiting a set of binary stars.

“Where the Nightlife Never Ends” for an orphan planet no longer orbiting a sun.

A super-Earth and its gravity (NASA/JPL)
A super-Earth and its gravity (NASA/JPL-Caltech)

“Experience the Gravity of HD 40307d for a super-Earth where the force of gravity would be much stronger than on Earth.

“Where the Grass is Always Redder on the Other Side” for a planet orbiting a sun cooler than ours and emitting radiation in redder wavelengths.

Given the huge success of the posters, the logical question to ask is whether more are coming, and when.

I certainly asked the question but those who know said they couldn’t answer.

Nonetheless, I think there’s reason to be optimistic that more clever and compelling planetary and exoplanetary art will be coming out of the JPL “Studio” in the months and years ahead.  And some will no doubt be retro.

So stay tuned.

Joby Harris (left) and Dan Goods in "The Studio" at JPL. (NASA/JPL)
Joby Harris (left) and Dan Goods in “The Studio” at JPL. (NASA/JPL-Caltech)
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France and Exoplanets

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Artist impression of the CoRot (COnvection ROtation and planetary Transits) space telescope. A French-led mission, it launched in 2006 and send back images until 2012. (ESA)
Artist impression of the CoRot (COnvection ROtation and planetary Transits) space telescope. A French-led mission, it launched in 2006 and send back images until 2012. (ESA)

For reasons all too regrettable, it seems appropriate today to highlight the extensive work being done in France and by French scientists to move forward the science of exoplanets.

The American public tends to view space observatories and exoplanet research as largely the domain of NASA and our nation. While we are leaders for sure, others are adding considerably to the field and to the world’s knowledge. And few nations have been as involved in the search for faraway worlds and efforts to understand them than France, and the work there will clearly continue.

“The French have been major contributors in the exoplanet field,” said David Latham, a senior astronomer at the Harvard-Smithsonian Center for Astrophysics, who has worked a lot with French colleagues.  “It’s spanned several decades now — from the detection of our first exoplanet (51 Pegasi b) on a French telescope to the large number of talented young French exoplanet researchers you see everywhere today.”

Probably the greatest single French contribution to exoplanet study has been the five-year run of the CoRoT (Convection, Rotation, and planetary Transits) spacecraft. Launched in 2006 – three years before our Kepler Space Telescope – it pioneered the space-borne detection and initial characterizing of exoplanets using the transit method. CoRoT was not as powerful as Kepler in its ability to see into space, but it did end up finding more than 30 exoplanets using the same transit method of detection, with more than 100 additional planet candidates awaiting confirmation.

This artist’s impression shows the transiting exoplanet Corot-9b. Discovered by combining observations from the CoRoT satellite and the ESO HARPS instrument, Corot-9b is the first “normal” exoplanet that can be studied in great detail. This planet has the size of Jupiter and an orbit similar to that of Mercury. It orbits a star similar to the Sun located 1,500 light-years away from Earth towards the constellation of Serpens (the Snake). Corot-9b passes in front of its host star every 95 days, as seen from Earth. This “transit” lasts for about 8 hours. Like our own giant planets, Jupiter and Saturn, the planet is mostly made of hydrogen and helium, and it may contain up to 20 Earth masses of other elements, including water and rock at high temperatures and pressures.
This artist’s impression shows the transiting exoplanet Corot-9b. Discovered by combining observations from the CoRoT satellite and the European Southern Observatory HARPS instrument, Corot-9b was among the first “normal” exoplanets that could  be studied in great detail. Corot-9b passes in front of its host star every 95 days, as seen from Earth. This “transit” lasts for about 8 hours. Like our own giant planets, Jupiter and Saturn, the planet is mostly made of hydrogen and helium, and it may contain up to 20 Earth masses of other elements, including water and rock at high temperatures and pressures. (ESO)

One of its most significant contributions was the discovery of the first definitively rocky exoplanet, COROT-7b. Less than twice Earth’s size and roughly the same density, it orbits its Sun-like star every 20 hours and is so likely molten. It was a surprising discovery for a telescope designed to find Jupiter-size planets.

The satellite mission was a collaboration of the French space agency, the Centre National d’Etudes Spatiales (CNES) and European space agencies, but France paid much of the cost and French scientists and engineers designed and made most of the instruments.

The head of the CoRoT exoplanet program was Magali Deleuil from Laboratoire d’Astrophysique de Marseille. Her handling of the project was so strong that she was appointed to oversee two upcoming European exoplanet missions – Cheops (scheduled to launch in 2017, with Swiss leadership) and Plato (planned for 2024 and led by Germany.)

Magali Deleuil, head of exo-planet research for CoRot. Magali Deleuil, head of exo-planet research for CoRot
Magali Deleuil, head of exo-planet research for CoRot

Cheops (the CHaracterizing ExOPlanet Satellite) is designed primarily to further study exoplanets identified by CoRoT and Kepler and measure their radii, while the goal of the more sophisticated Plato (Planetary Transits and Oscillations of stars) mission is to find planets like Earth, in terms of both size and potential habitability. Plato will have a much larger field of view than Kepler, and so will be able to see far more stars and exoplanets.

The principal investigator for CoRoT was Annie Baglin, senior researcher at the Paris Observatory. Her main field of research is stellar physics and her major interest is now stellar seismology – the deep internal vibrations that regularly shake our sun and others. These dynamics of stars have become increasingly important as a method to understand what is going on in their interiors, and to tease out some aspects of their composition.

Annie Baglin giving the final command to CoRoT in 2014, sending it out of orbit. The pioneering telescope sent back planet transit images for six years. (CNES)

In 1964, France became one of the founding members of the European Southern Observatory, a consortium now of 17 nations that has together planned, funded and completed construction of four of the most important ground-based telescopes in the world. All are in Chile, and have made significant contributions to exoplanet research.  (That observatory where 51 Peg was discovered is the Haute-Provence Observatory, which opened more than seventy years  in southeastern France and is still operating.)

Another ESO telescope is scheduled to come on line in 2024, and it will have the largest mirror by far in the world – more than 39 meters across. The European Extremely Large Telescope has as one of its primary goals the detection and characterizing of exoplanets.

The European Southern Observatory’s Extremely Large Telescope compared in size with the ESO’s Very Large Telescope and the coliseum of Rome. (ESO)

France has also been the lead European nation in the development and operation of the Ariane family of rockets, and an Ariane 5 will launch the James Webb Space Telescope into space in 2018.

And there has also been a steady flow of French exoplanet researchers to American institutions, and vice versa. Francois Forget, for instance, has worked on climate modeling of exoplanet atmospheres at the NASA Ames Research Center in California, and is now a senior researcher at the Institut Pierre Simon Laplace Universite in Paris.   His work on exoplanet atmospheres is highly respected world.

Francois Forget, a highly-respected modeler of exoplanet atmospheres.
Francois Forget, a highly-respected modeler of exoplanet atmospheres.

American Sean Raymond of Laboratoire d’Astrophysique de Bordeaux in France, has seen that exoplanet focus in action.

“There is indeed a lot of exoplanet research in France,” he said.  “In some subjects such as planet formation, I would say that France is doing as much or more than any other country.”

Similarly, David Latham’s CfA published results last week about a planet with a radius only 1.2 times that of Earth, and both relatively close to our solar system and with a star that gives it good definition.  The planet, Gliese 1132b, is expected to be a prime candidate for study well into the future.

As Latham pointed out, five of the co-authors were from France.

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On Super-Earths, Sub-Neptunes and Some Lessons They Teach

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Part 1 of 2

The discovery of a menagerie of exoplanets sized greater than Earth and smaller than Neptune has changed thinking about planets and solar systems. The radius of Neptune is almost 4 times greater than Earth’s, and the planet’s mass is 17 times greater than our planet. (NASA)
The discovery of a menagerie of exoplanets sized greater than Earth and smaller than Neptune has changed thinking about planets and solar systems. The radius of Neptune is almost 4 times greater than Earth’s, and the planet’s mass is 17 times greater than our planet. (NASA)

When the first exoplanet was identified and confirmed 20 years ago, there was enormous excitement, a sense of historic breakthrough and, with almost parallel intensity, sheer bewilderment. The planet, 51 Pegasi B, was larger than Jupiter yet orbited its parent star in 4 days. In other words, it was much closer to its star than Mercury is to ours and so was extremely hot.

According to theories of the time about planetary formation and solar system organization, a hot Jupiter so close to its sun was impossible. That kind of close-in orbit is where small rocky planets might be found, not Jupiters that belonged much further out and were presumed to always be cold.

That was a soberingly appropriate introduction to the new era of exoplanets, and set the stage for 20 years of surprises and re-evaluations of long held theories and understandings.

While the presence of close-in hot Jupiters certainly remains one of the great puzzles of the exo-planet era, the most consequential exoplanetary revelation has likely been the discovery of many planets larger than Earth and smaller than the next largest planet in our solar system — icy, gaseous Neptune.

These “super-Earths’ and “sub-Neptunes” range greatly in size since Neptune has a radius four times greater than our planet. What’s so surprising about the presence of this class of planets is that they are not just common, they are by far the most frequently detected exoplanets to date.

Unknown
Kepler exoplanets candidates, both confirmed and unconfirmed, orbiting G, K, and M type main sequence stars, by radii and fraction of the total. (Natalie Batalha and Wendy Stenzel, NASA Ames)

Perhaps most intriguing of all, however, is their absence in our planetary line-up.

It has long been predicted that the planetary make-up of our solar system would be typical of others, but now we know that is (again) wrong. As Mark Marley, a staff scientist at NASA’s Ames Research Center who studies exoplanets put it, the widespread presence of “super-Earths” elsewhere and their absence in our system “is telling us something quite important.” The work to tease out what that might be has just begun, and will likely keep scientists busy for some time.

“It certainly seems that the universe wants to makes these planets,” Marley told me. “And they’re surprising not only because nobody predicted their vast number but also because they have been intractable – very, very difficult to characterize. It seems like they want to keep their secrets close to the vest.”

How are these planets keeping their secrets – the ingredients of their atmospheres, in particular – from researchers?   Because many seem to be surrounded by thick clouds and layers of sooty smog, like Los Angeles on a very bad day. As a result, the spectroscopy normally used to read exoplanet atmospheres and determine what elements and compounds are present is of little use. The instruments can’t see through the thick film

This helps explain why many astronomers and planetary scientists don’t like the term “super-Earths.” The word implies that they are sized-up Earths, but there’s every reason to believe that very few fit into that category. Nonetheless, the name is so compelling that, for now at least, it seems to have stuck – with that addition of “sub-Neptunes.”

This artist's illustration represents the variety of planets being detected by NASA's Kepler spacecraft. A new analysis has determined the frequencies of planets of all sizes, from Earths up to gas giants. (C. Pulliam & D. Aguilar, CfA)
This artist’s illustration represents the variety of planets being detected by NASA’s Kepler spacecraft. A new analysis has determined the frequencies of planets of all sizes, from Earths up to gas giants. (C. Pulliam & D. Aguilar, CfA)

Despite the difficulties in characterizing these planets, some progress is being made. Researchers Leslie Rogers of Caltech and Lauren Weiss at Berkeley have separately, for instance, determined which super-Earths and mini-Neptunes are likely to be rocky like Earth and which are likely to be gaseous and icy like Neptune.  The cut-off is by no means precise or across-the-board, but it appears that once a planet has a radius more than 1.5 or 1.6 times the size of Earth, it will most likely have a thick gas envelope of hydrogen, helium and sometimes methane and ammonia around it.

Weiss, a Ken & Gloria Levy Graduate Student Fellow, described some other super-Earth/sub-Neptune characteristics that she and others have found. These exoplanets, for instance, very often have nearby companions in the same class. Many of these larger ones (above 1.5 Earth radii) also tend to be fluffy; quite big but not particularly dense. Weiss likens the least dense super-Earths to macarons – a light, French meringue-based confection (that is definitely not a macaroon.)

They may well have cores of iron and some inner rockiness, but they are so light that they have to consist in large part of hydrogen, helium, water and other gases. It is common to find super-Earths and even sub-Neptunes that have much larger diameters than Earth, but have less mass than Earth.

While some of the super-Earths and sub-Neptunes were, and still are being detected using ground-based radial velocity and other techniques, most were found by Kepler.  That means the field is very young because that early data came out only a few years ago.  But it represents such an important and compelling paradigm shift in astronomy and planetary science that a large and growing contingent of researchers has quickly assembled to search for and study these properly high-profile planets – their orbits, their planetary neighbors, their masses, and now to some extent the make-up of their atmospheres and cores. Some of the work involves observation, some theory and some modeling.

As Mark Marley pointed out, these planets are not giving up their secrets easily. And inevitably, given the great interest and limited data, conclusions and findings will be published that appear strong at the time, but are quickly eclipsed by new information.

Take, for instance, the announced interpretation in 2009, 2012 and 2013 of a sub-Neptune size “water world.” While the papers that introduced the possibility of a very wet exoplanet Gliese 1214b contained caveats, the news stories that went around the world reported that the first water world had apparently been discovered. Exciting news, for sure.

The planet Gliese 1214b was initially described as a possible "water world," and the idea caught the public imagination. But subsequent examination, and the characterizing of other super-Earths and sub-Neptunes, has led to a different conclusion: that the planet is most likely covered by a hydrogen/helium envelope and a thick film of sooty dust. (Artist rendering by L. Calçada, European Space Observatory.)
The planet Gliese 1214b was initially described as a possible “water world,” and the idea caught the public imagination. But subsequent examination, and the characterizing of other super-Earths and sub-Neptunes, has led to a different conclusion: that the planet is most likely covered by a hydrogen/helium envelope and a thick film of sooty dust. (Artist rendering by L. Calçada, European Space Observatory.)

But several years later, it is clear that the water world story was premature. The presence of water had never been confirmed for Gleise 1214b, but rather had been inferred by other limited measurements involving mass, radius, and the absence of spectral data, which were together interpreted to mean the possible, or even probable, presence of a steamy, wet atmosphere.

It still may be the case that the planet has abundant water. But follow-up investigation using the Hubble Space Telescope showed conclusively that the planet was covered in clouds of unknown make-up and origin, and that the presence of massive amounts of water could not be properly inferred from the data at hand.

Zachory Berta-Thompson of MIT was one of the key participants in the Gliese 1214b papers, and he agrees that the evidence today does not point to a water world.  “There was a very deep investigation of the GJ 1214b atmosphere with the Hubble, and if water was there it would have been detected,” he said.  (The lead author of that paper was Laura Kreidberg of the University of Chicago.)

“We used the data we had when the planet was discovered, and made calculations and inferences that made sense at the time,” Berta-Thompson said.  “But the field moves quickly and with the discovery of many other sub-Neptunes, we would draw other conclusions.”  Gliese 1214b, he said, is most likely a puffy planet (with an envelope of hydrogen and helium) rather than a water world.

This is not, it should be noted, a knock on the initial paper. If anything, it’s a knock on journalists (of which I have long been one) who highlighted the water world story. But primarily, the Gliese 1214b research is one of numerous examples of the exciting new science of super-Earths and sub-Neptunes playing out at very high speed, with inevitable potholes on a bumpy and terribly hard-to-navigate road.

 

Many Worlds will continue this discussion of super-Earths and sub-Neptunes on Friday, with an emphasis on thinking about whether they might be conducive or anathema to life.

 

 

 

 

 

 

 

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Counting Our Countless Worlds

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The Milky Way has several hundred billion stars, and many scientists are now convinced it has even more planets and moons. (NASA)
The Milky Way is home to several hundred billion stars, and many scientists are now convinced it has even more planets and moons. (NASA)

Imagine counting all the people who have ever lived on Earth, well over 100 billion of them.

Then imagine counting all the planets now orbiting stars in our Milky Way galaxy , and in particular the ones that are roughly speaking Earth-sized. Not so big that the planet turns into a gas giant, and not so small that it has trouble holding onto an atmosphere.

In the wake of the explosion of discoveries about distant planets and their suns in the last two decades, we can fairly conclude that one number is substantially larger than the other.

Yes, there are many, many billions more planets in our one galaxy than people who have set foot on Earth in all human history. And yes, there are expected to be more planets in distant habitable zones as there are people alive today, a number upwards of 7 billion.

This is for sure a comparison of apples and oranges. But it not only gives a sense of just how commonplace planets are in our galaxy (and no doubt beyond), but also that the population of potentially habitable planets is enormous, too.   “Many Worlds,” indeed.

The populations of exoplanets identified so far, plotted according to the radius of the planet and how many days it takes to orbit. The circles in yellow represent planets found by Kepler, light blue by using ground-based radial velocity, and pink for transiting planets not found by Kepler, and green, purple and red other ground-based methods. (NASA Ames Research Center)
The populations of exoplanets identified so far, plotted according to the radius of the planet and how many days it takes to orbit. The circles in yellow represent planets found by Kepler, light blue by using ground-based radial velocity, and pink for transiting planets not found by Kepler, and green, purple and red other ground-based methods. (NASA Ames Research Center)

It was Ruslan Belikov, an astrophysicist at NASA’s Ames Research Center in Silicon Valley who provided this sense of scale.  The numbers are of great importance to him because he (and others) will be making recommendations about future NASA exoplanet-finding and characterization missions based on the most precise population numbers that NASA and the exoplanet community can provide.

Natalie Batalha, Mission Scientist for the Kepler Space Telescope mission and the person responsible for assessing the planet population out there, sliced it another way. When I asked her if her team and others now expect each star to have a planet orbiting it, she replied: “At least one.”

Kepler-186f was the first rocky planet to be found within the habitable zone -- the region around the host star where the temperature is right for liquid water. This planet is also very close in size to Earth. (NASA Ames/SETI Institute/JPL-Caltech)
Kepler-186f was the first rocky planet to be found within the habitable zone — the region around the host star where the temperature is right for liquid water. This planet is also very close in size to Earth. (NASA Ames/SETI Institute/JPL-Caltech)

I caught up with Belikov, Batalha and several dozen others intimately involved in cataloguing the vast menagerie of exoplanets at a “Hack Event” earlier this month at Ames. The goal of the three-day gathering was to find ways to improve the already high level of reliability and completeness regarding planets identified by Kepler.

It also provided an opportunity to learn more about how, exactly, these scientists can be so confident about the very large numbers of exoplanets and habitable zone exoplanets they describe. After all, the total number of confirmed exoplanets is a bit under 2,000 – a majority found by Kepler but hundreds of others by pioneering astronomers using ground-based telescopes and very different techniques. Kepler has another 3,000 planet candidates that scientists are in the process of analyzing and most likely confirming, but still. Four thousand is minuscule compared with two hundred billion.

Not everyone completely agrees that we’re ready to estimate such large numbers of exoplanets—suggesting that we need more data before making such important estimates — but the community consensus is that their extrapolations from current data are solid and scientific. And here is why:

The Kepler telescope looks out at a very small portion of the sky with a limited number of stars – about 190,000 of them during its four year survey. And it identifies planets based on the tiny dimming of stars when an object (almost always a planet) crosses between the star and the telescope.

The Kepler telescope looked constantly for four years at almost 200,000 stars in the Cygnus constellation. (Carter Roberts)
The Kepler telescope looked constantly for four years at almost 200,000 stars in the Cygnus & Lyra constellations.  Its lens is always open, by design. (Carter Roberts)

By identifying those 4,000-plus confirmed and candidate planets over four years, Kepler infers the existence of many, many more. As Batalha explained, a transit of the planet is only observable when the orbit is aligned with the telescope, and the probability of that alignment is very small. Kepler scientists refer to this as a “bias” in their observations, and it is one that can be quantified. For example, the probability that an Earth-Sun twin will be aligned in a transiting geometry is just 0.5%. For every one that Kepler detects, there are 200 others that didn’t transit simply because of the orientation of their orbits.

Then there’s the question of faintness and reliability. Kepler is looking out at stars hundreds, sometimes thousands of light years away.  The more distant a star, the fainter it is and the more difficult it is to gather measurements of –and especially dips in — brightness. When it comes to potentially habitable, Earth-sized planets, Batalha said that only 10,000 to 15,000 of the stars observed are bright enough for planets to be detectable even if they do transit the disk of their host star.

Here’s why: Detecting an Earth-sized planet would be roughly equivalent to capturing the image of a gnat as it crosses a car headlight shining one mile away. For a Jupiter-size planet, the bug would grow to only the size of a large beetle.

Add this bias to the earlier one, and you can see how the numbers swell so quickly. And since Kepler’s mission has been to provide a survey of planets in one small region – and not a census – this kind of statistical extrapolation is precisely what the mission is supposed to do.

There are numerous other detecting challenges posed by the dynamics of exoplanets, stars and the great distances. But then there are also innumerable challenges associated with the workings of the 95 megapixel CCD array that is collecting light for Kepler.   “Sensitivity dropouts” caused by those cosmic rays, horizontal “rolling bands” on the CCDs caused by temperature changes in the electronics, “optical ghosts” from binary stars that create false signals of transits on nearby stars — they are some of the many instrument artifacts that can be mistaken as a drop in light coming from a planet. Kepler’s data processing pipeline, much of which has been transferred over to the NASA Ames supercomputer, has the job of sorting all this out.

 

After the CCDs on the Kepler telescope record the light from stars in its viewing field, the data is sent back to Earth and goes through numerous steps before possibly delivering a “Kepler object of interest,” and possibly a planet candidate. Pleiades is the Ames supercomputer. (NASA Ames)
After the CCDs on the Kepler telescope record the light from stars in its viewing field, the data is sent back to Earth and goes through numerous steps before possibly delivering a “Kepler object of interest,” and possibly a planet candidate. Pleiades is the Ames supercomputer. (NASA Ames)

Adding to the challenge, said Jon Jenkins, a Kepler co-investigator at Ames and the science lead for the pipeline development, is that the stars viewed by Kepler turned out to be themselves “noisier” than expected. Stars naturally vary in their overall brightness, and the data processing pipeline had to be upgraded to account for that changeability.  But that stellar noise has played a key role in keeping Kepler from seeing some of the small planet transits that the team hoped to detect.

What the Hack event and other parallel efforts are doing is finding ways to, as Jenkins put it, “dig into the noise…to move towards the hairy edge of what our data can show.” The final goal: “To come up with the newest, best washer we can to clean the data and come out with an improved catalog of sparkling planets.”

All the data that will come from the primary Kepler mission, which came to a halt in the summer of 2013, has been collected and analyzed already on a first round. But now the entire pipeline of data is going to be reprocessed with its many improvements so the researchers can dig deeper into data trove. Batalha said they hope to find planets – especially Earth-sized planets – this way.

One of the key techniques to measure the performance of Kepler’s analysis pipeline is to inject fake transit signals into the data and see if it picks up their presence. As Batalha explained, this provides another way to gauge the biases in the system, its efficiency at detecting the planets that it could and should see. “If we inject 100 fake things into the pipeline and find 90 of them, that’s means we’re 90 percent complete.” She said the number would then be worked into the calculations of how many planets are out there, and how many of certain sizes will be caught and missed.

Natalie Batalha is the Chief Scientist for the Kepler mission, while announcing the discovery of Kepler’s first rocky planet, Kepler-10b, in January 2011.

So the Hack Event, which brought together astrophysicists, planetary scientists and computer hakers, was designed to come up with ways to improve Kepler’s completeness (seeing everything there to be seen) and reliability (the likelihood that the signal comes from a planet and not an instrument artifact or non-planetary phenomena in space). By computing both the completeness and reliability, scientists are confident that they can eliminate the observation biases and transform the discovery catalog into a directory of actual planets.

This is one of the key accomplishments of the Kepler mission – making it scientifically possible to say that there are billions and billions of planets out there. What’s more, the increased power of Kepler allowed for the discovery of smaller planets, which are now known to make up the bulk of the exoplanets. And while the number of Earth-sized planets detected in that habitable zone is small – around thirty – that’s still quite a remarkable feat. And remember, Kepler is looking at but one small sliver of the sky.

The twelve exoplanets detected so far closest to Earth in size, lined up with the type of stars they orbit. (NASA Ames)
The twelve exoplanets detected and confirmed so far closest to Earth in size, lined up with the type of stars they orbit. (NASA Ames)

Why does it matter how many exoplanets are out there, how many are rocky and Earth-sized, and how many within habitable zones? The last twenty years of exoplanet hunting, after all, has made clear that there are an essentially infinite number of them in the universe, and untold billions in our galaxy.

The answer lies in the insatiable human desire to know more about the world writ large, and how and why different stars have very different solar systems. But more immediately, there’s the need to know how to best design and operate future planet-finding missions. If the goal is to learn how to characterize exoplanets – identify components of their atmospheres, learn about their weather, their surfaces and maybe their cores – then scientists and engineers need to know a lot more about where planets generally, and some specifically, can be found. And those planet demographics just might open some surprising possibilities.

For instance, Belikov and his Ames colleague Eduardo Bendek have proposed a NASA “small explorer” (under $175 million) mission to launch a 30-to-45 centimeter mirror designed to look for Earth-sized planets only at our nearest stellar neighbor, Alpha Centauri. That’s as small a telescope as you can buy off-the-shelf.

Alpha Centauri is the closest star system to our Solar System at about 4.37 lightyears away. (NASA/Hubble Space Telescope)
Alpha Centauri is the closest star system to our Solar System at about 4.37 lightyears away. (NASA/Hubble Space Telescope)

Alpha Centauri is a two-star system, and until recently researchers doubted that binaries like it would have orbiting planets. But Kepler and other planet hunters have found that planets are relatively common around binaries, making Alpha Centauri a better target than earlier imagined.

To make it a truly viable project, ACESat – the Alpha Centauri Exoplanet Satellite – requires something else: a scientifically sound estimate of the likelihood that any star in our galaxy would have an Earth-sized planet in its system. Estimates so far have ranged from 10 percent to 50 percent, but Belikov said newer data is encouraging.

“If that number becomes more firm and approaches 50 percent, then an Alpha Centauri-only mission makes a great deal of sense,” he said. “For a small investment, we could have a real possibility of detecting a planet very close by.”

Intriguing, and an insight into how new space missions are designed based on the science already completed. Both NASA and the European Space Agency have plans to launch three significant exoplanet missions within the decade, and the powerful James Webb Space Telescope will launch in 2018 with some known and undoubtedly some not yet understood capabilities for exoplanet discovery. And perhaps most important, NASA is about to study how a potential mission in the 2030s could be designed with the specific purpose of directly imaging exoplanets – the gold standard for the field. All are being designed based on current exoplanet understandings, including the abundance calculations enabled by the Kepler mission’s observations.

Almost 2,000 exoplanets have now been identified, more than half by Kepler. Another 3,000 exoplanet candidates await confirmation. (NASA Ames)
Almost 2,000 exoplanets have now been detected and confirmed, more than half by Kepler. Another 3,000 exoplanet candidates await confirmation. (NASA Ames)

Future posts will dig deeper into a fair number of the subjects raised here, but for now this much is clear: Our galaxy has many billions of planets, and the process of detecting them is robust and on-going, the process of characterizing them has begun, and all the signs point towards the presence of enormous numbers of planets in habitable zones that, in the biggest picture at least, could possibly support life.

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The Exoplanet Era

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Many, and perhaps most stars have solar systems with numerous planets, as in this artist rendering of Kepler 11. (NASA)

Throughout the history of science, moments periodically arrive when new fields of knowledge and discovery just explode.

Cosmology was a kind of dream world until Edwin Hubble established that the universe was expanding, and doing so at an ever-faster rate. A far more vibrant and scientific discipline was born. On a more practical level, it was only three decades ago that rudimentary personal computers were still a novelty, and now computer-controlled, self-driving cars are just on the horizon. And not that long ago, genomics and the mapping of the human genome also went into hyperspeed, and turned the mysterious into the well known.

Most frequently, these bursts of scientific energy and progress are the result of technological innovation, coupled with the far-seeing (and often lonely and initially unsupported) labor and insights of men and women who are simply ahead of the curve.

We are at another of those scientific moments right now, and the subject is exoplanets – the billions (or is it billions of billions?) of planets orbiting stars other than our sun.

The 20th anniversary of the breakthrough discovery of the first exoplanet orbiting a sun, 51 Pegasi B, is being celebrated this month with appropriate fanfare. But while exoplanet discovery remains active and planet hunters increasingly skilled and inventive, it is no longer the edgiest frontier.

Now, astronomers, astrophysicists, astrobiologists, planetary scientists, climatologists, heliophysicists and many more are streaming into a field made so enticing, so seemingly fertile by that discovery of the apparent ubiquitiousness of exoplanets.

The new goal: Identifying the most compelling mysteries of some of those distant planets, and gradually but inexorably finding ever-more inventive ways to solve them. This is a thrilling task on its own, but the potential prize makes it into quite an historic quest. Because that prize is the identification of extraterrestrial life.

The presence of life beyond Earth is something that humans have dreamed about forever – with a seemingly intuitive sense that there just had to be other planets out there, and that it made equal sense that some of them supported life. Hollywood was on to this long ago, but now we have the beginning technology and fast-growing knowledge to transform that intuitive sense of life out there into a working science.

The thin gauzy rim of the planet in foreground is an illustration of its atmosphere. (NASA’s Goddard Space Flight Center)
The thin gauzy rim of the planet in foreground is an illustration of its atmosphere. (NASA’s Goddard Space Flight Center)

Already the masses and orbits of several thousand exoplanets have been measured. Some planets have been identified as rocky like Earth (as opposed to gaseous like Jupiter.) Some have been found in what the field calls “habitable zones” – regions around distant suns where liquid water could plausibly run on a surface –as it does on Earth and once did on Mars. And some exoplanets have even been determined to have specific compounds – carbon dioxide, water, methane, even oxygen – in their atmospheres.

This and more is what I will be exploring, describing, hopefully bringing to life through an on-going examination of this emerging field of science and the inventive scientists working to understand planets and solar systems many light-years away. Theirs is a daunting task for sure, and progress may be halting. But many scientists are convinced that the goal is entirely within reach – that based on discoveries already made, the essential dynamics and characteristics of very different kinds of planets and solar systems are knowable. Thus the name of this offering: “Many Worlds.”

Artist rendering of early stages of planet formation in the swirl and debris of the disk of a new star. (NASA/JPL-Caltech)
Artist rendering of early stages of planet formation in the swirl and debris of the disk of a new star. (NASA/JPL-Caltech)

I was first introduced to, and captivated by, this cosmic search in a class for space journalists taught by scientists including Sara Seager, a dynamic young professor of physics and planetary science at M.I.T., a subsequently-selected MacArthur “genius,” and a pioneer in the field not of discovering exoplanets, but of characterizing them and their atmospheres. And based on her theorizing and the observations of many others, she was convinced that this characterizing would lead to the discovery of very distant extraterrestrtial life, or at least to the discovery of planetary signatures that make the presence of life highly probable. Just this week, she predicted the discovery could take place within a decade.

It was in 2010 that she began her book “Exoplanet Atmospheres” with the statement: “A new era in planetary science is upon us.” I would take it further: A new era has arrived in the human drive to understand the universe and our place in it. Exoplanets and their solar systems are a magnet to young scientists, says Paul Hertz, the head of NASA’s Astrophysics Division. Almost a third of the papers presented at astronomy conferences these days involve exoplanets, he said, and “it’s hard to find scientists in our field under thirty not working on exoplanets.” Go to a major geology conference, or a planetary science meeting, and much the same will be true.

And why not? I think of this moment as akin to the time in the 17th century when early microscopes revealed a universe of life never before seen. So many new questions to ask, so many discoveries to make, so much exciting and ultimately world-changing science ahead.

But the challenge of characterizing exoplanets and some day identifying signs of life does not lend itself to the kind of solitary or small group work that characterized microbiology (think the breakthrough NASA Kepler mission and the large team needed to make it reality and to analyze its results.) Not only does it require costly observatories and telescopes and spectrometers, but it also needs the expertise that scientists from different fields can bring to the task – rather like the effort to map the human genome.

That is the organizing logic of astrobiology – the more general hunt for life elsewhere in our solar system and far beyond, alongside the search for clues into how life may have started on our planet. NASA is eager to encourage that same spirit in the more specific but nonetheless equally sprawling exploration of exoplanets, their atmospheres, their physical makeup, their climates, their suns, their neighborhoods.

The Earth alongside “Super-Earth-” sized exoplanets identified with the Kepler Space Telescope. (NASA Ames / JPL-Caltech)
The Earth alongside “Super-Earth-” sized exoplanets identified with the Kepler Space Telescope. (NASA Ames / JPL-Caltech)

The result was the creation this summer of the the Nexus for Exoplanet System Science (NExSS), a group that will be led by 17 teams of scientists from around the country already working on some aspect of the rich exoplanet opportunity. The group was selected from teams that had applied for grants from NASA’s Astrobiology Institute, an arm of its larger NASA Astrobiology Program, as well as other NASA programs in the Planetary Sciences, Astrophysics and Astronomy divisions.

Their mandate is to spark new approaches in the effort to understand exoplanets by identifying areas without consensus in the broader community, and then fostering collaborations here and abroad to address those issues. “Many Worlds” grew out of the NExSS initiative, and will chronicle and explain the efforts of some team members as they explore how exo-plants and exo-creatures might be detected; what can be learned from afar about the surfaces and cores of exoplanets and how both play into the possibility of faraway life; the presence and dynamics of exo-weather, what we can learn about exoplanets from our own planet and solar system, and so much more.

A few of the teams are small, but many are quite large, established and mature – perhaps most especially the Virtual Planetary Laboratory at the University of Washington, and run by Victoria Meadows. Since 2001, the virtual lab has collaborated with researchers representing many disciplines, and from as many as 20 institutions, to understand what factors might best predict whether an exoplanet harbors life, using Earth as a model.

But just as I will be venturing beyond NExSS in my writing about this new era of exploration, so too will NExSS be open to the involvement of other scientists in the field. The original group has been tasked with identifying an agenda of sorts for NASA exoplanet missions and efforts ahead. But its aim is to be inclusive and its conclusions and recommendations will only be as useful and important as the exoplanet community writ large determines them to be.

The Carina Nebula, one of many regions where stars come together and planets later form made out of the surrounding dust, gas and later rock. (NASA, ESA, and the Hubble SM4 ERO Team)
The Carina Nebula, one of many regions where stars come together and planets later form made out of the surrounding dust, gas and later rock. (NASA, ESA, and the Hubble SM4 ERO Team)

This is a moment pregnant with promise. Systematically investigating exoplanets and their environs is an engine for discovery and a pathway into that largest question of whether or not we are alone in the universe.

Will scientists some day find worlds where donkeys talk and pigs can fly (as at least one “everything is possible” philosopher has posited)? Unlikely.

But just as microscopes and the scientists using them led to the science of microbiology and most of modern medicine, so too are our orbiting observatories, Earth-based telescopes and the scientists who analyze their results are regularly opening up a world of myriad and often surprising marvels.

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