I mean no disrespect when I say that Mike Brown is a man on the edge. In fact, it is one of the highest forms of praise I can imagine. Brown, an astronomer at Caltech, has been one of the most aggressive scientific explorers of the dark, outer boundaries of the solar system. His campaign to extend human vision into the poorly understood region beyond Neptune led to the discovery of a whole menagerie of large object including Pluto’s near-twin, Eris. That work led to the official demotion of Pluto from planet to “dwarf planet.”
Brown has no regrets (he proudly calls himself @plutokiller on Twitter), not because he considers Pluto unimportant but because he considers the whole vast region beyond Neptune so hugely important for understanding the evolutionary history of Earth and the rest of the solar system. Most recently, Brown and his colleague Konstantin Batygin tracked down strong evidence for Planet 9, a large planet–about 10 times the mass of Earth–orbiting at least 200 times as far from the sun as we are. The announcement made headlines around the world. But Planet 9 is still just a beginning.
When I was a kid and got hooked on astronomy (sometime around age 7), one of the things I deeply enjoyed about the night sky was its constancy. The human world is full of unwanted variables: Families move, friends get into fights with you, bicycles crash, birthday parties don’t turn out the way you wanted…but all you have to do is look up and you can make contact with another realm that never produces such disappointments. The stars are always in the same places. The planets slide around in the sky, but they don’t really change. Every time you see Jupiter, it is the same old reliable Jupiter.
Except that it isn’t. The closer you look at the solar system, the more you see change happening, and on all time scales. The constancy was an illusion, created by humans (not just my younger self!) watching the sky too erratically and too impatiently to see what is really going on. Jupiter is not always the same old Jupiter, as is abundantly clear from amateur video showing the planet getting whacked by a small asteroid or comet on the night of March 17. Watch other worlds and you’ll see the same thing happening. Wait longer–quite long by human standards, but very short in astronomical terms–and some really weird, extreme events unfold.
The recent discovery of gravitational waves by the twin LIGO detectors drove home the gaping chasm between the popular image of how astronomers explore the cosmos and the way it actually happens. In the layperson’s view — which, to be fair, aligns well with daily experience of how we find out new things — exploration is a matter of looking, seeing, and understanding. In reality, most of what astronomers do involves looking without seeing, or seeing without understanding. It involves not just working at the edge of perception, but trying to deduce what lies beyond perception.
At the risk of sounding unscientific, I’d call it cosmic ghost hunting.
By now you’ve probably heard the announcement that astronomers Konstantin Batygin and Mike Brown think they’ve tracked down “Planet 9,” a long-rumored large world orbiting in the distant wilderness of the solar system. Even if you haven’t heard, the news may sound familiar, since a confusingly similar but completely separate report made the rounds just a month ago. (Students of history will recall that Planet X stories also circulated in 2014 and 2006, and have been a staple of the astronomy hype machine all the way back to the discovery of Ceres in 1801.)
The dreary truth is that the Batygin and Brown claim, while stronger than the ones that came before, is still soaked in uncertainty. But there’s another truth, far more exciting, that goes with it: The latest efforts to find Planet X are hugely revealing, even if these particular ones don’t hold up.
Reason #1: The competing claims starkly illustrate the difference between seeing and believing. The case for Planet 9 is much stronger than for the ones described in December, even though researchers have directly observed the earlier objects but have not seen Planet 9 at all. Better yet is reason #2: These stories keep popping up because overwhelming majority of the solar system is cloaked in darkness, and is just now coming into view. Even the latest maybe-planets turn out not to exist, it’s nearly certain that there are big, exotic things out beyond Pluto waiting to be found.
What was the biggest news in astronomy this past year? The editorial board of Discover has helpfully provided an answer, one that I heartily endorse (and not only because I wrote the related story in the magazine): It was the exploration of Pluto by the New Horizons spacecraft. To appreciate just why that mission was, and still is, such a big deal, join me in a little act of mental time travel.
If you could move 6 months back in time, it would be shockingly simple to summarize what astronomers knew about Pluto–and mind you, they knew more about Pluto than about any of the other myriad frozen worlds out beyond Neptune. The Idiot’s Guide to Pluto would not include an exact diameter (nobody knew it), or structure of the atmosphere, the geology, the topography, the composition, or even Pluto’s distinctive markings (nobody knew any of those, either).
It can feel inappropriate celebrating the exploration of the universe while the media are saturated with grim stories about warfare, terrorism, and other forms of human suffering. The issue boils down to matters of sensitivity and propriety: How can you talk about something so theoretical and remote when there are so many problems all around us? I wrote a column on this theme last year, and it feels especially timely right now as I (like so many other Americans) am stepping back to think about the things I’m thankful for.
What really struck me from that perspective was the sense of progress: The old-fashioned sense of forward motion through history, from less civilized to more, toward a better and more fulfilling lifestyle for all of humanity. It is easy to lose sight of the pattern while being barraged by news stories that give the impression we are living in the worst time ever–but by most measures, we are living in the best time ever. I’m not talking just about scientific exploration (in which 2015 witnessed historic explorations the small worlds Pluto and Ceres), but also about the overall quality of human life. Both are getting better and better, and the reasons why are intertwined.
With its strong showing at the box office, The Martian joins Gravity and Interstellar in the club of science-fiction movies that succeed by emphasizing the science and downplaying the anything-goes fantasy elements. But even in this rarefied company, The Martian stands apart. Unlike Interstellar, it is rooted in present-day technology and challenges. And unlike Gravity, it fully respects the physical rules of space travel; in fact, it makes them central to the plot.
The Martian comes at a pivotal time for NASA. With space imagery getting better and better–taking on an almost cinematic quality–the need for human exploration in some ways seems less obvious than ever. At the same time, the difficulty of getting any concrete answers about life on Mars (or even definitive answers about water and methane) illustrates the huge limitations of doing science using robots. Artificial intelligence and remote control are just not cutting it. By treating the human exploration of Mars with scientific respect and genuine emotion, The Martian make its case more powerfully than NASA’s slick posters and earnest Congressional testimony have managed to do.
The 20-year stretch since the discovery of the first exoplanet—a planet circling a star other than the sun—has seen a wholesale relocation of cool ideas from science fiction over to science fact. By 1999, scientists found a way to study the composition of exoplanets. By 2004, they identified a rocky planet, broadly similar to Earth in structure. By 2014, they tracked down an Earth-size world that is the right distance from its star for liquid water. The Star Trek vision of a galaxy full of habitable planets doesn’t look farfetched anymore.
Despite that remarkable progress, we are still far from answering the big question: Is anybody (or anything) out there? What we all want to find is not just an Earth-size world, or an Earth-temperature world, or a vaguely Earth-like world. We want to find Earth 2.0: a wet, warm, living, breathing planet just like our own. To do that, we need to go far beyond the search techniques that astronomers have used so far. There needs to be a more ambitious plan. And there is.
Twenty years ago today, an invisible object circling an obscure star in the constellation Pegasus overturned everything astronomers knew about planets around other stars. No, the fallout was even bigger than that. The indirect detection of 51 Pegasi b—the first planet ever found around a star similar to the sun—revealed that they had never really known anything to begin with.
At the time, even the most adventurous minds blithely assumed that our solar system was more or less typical, a template for all the others. 51 Peg b threw a big splash of reality in their faces. The newfound world was bizarre, a Jupiter-size world skimming the surface of its star in a blistering-fast “year” that lasted just 4.2 days. Its existence ran counter to the standard theories of how planets form and evolve. It answered one big question: Yes, other planetary systems really do exist. But it raised a thousand others.
NASA scientists were conferring today about a nearby planet that is shockingly similar to Earth. It is just 5% smaller in radius and 15% smaller in mass. It is almost the exact same age as our planet, and gets its warmth from an identical star. The only thing that’s a bit off is that it orbits a bit closer to its star than Earth does, so it receives nearly twice as much radiation. On the other, it also reflects away a lot of that radiation. Its theoretical (equilibrium) temperature is just below freezing, so with a little natural greenhouse warming it would be quite an inviting place.
If we found it orbiting another star, this world would surely be hailed as the most Earthlike exoplanet known: the best place yet to search for alien life.
No doubt you sense there is a catch, and indeed there is. The world I’m talking about is Venus. It is not orbiting another star; it is the planet closest to home right here in our own solar system. But I’m not just being coy. Despite its proximity, Venus is a profound enigma. It really should be a hospitable world, but the truth is that it is more like hell on almost-Earth. Understanding why that is–why our planet went right while Venus went terribly wrong–is crucial for finding out whether habitable planets are common or rare throughout the universe.