The Exoplanet Era

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 ubiquitousness 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 extraterrestrial 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.