Like many other space enthusiasts around the world, I woke up today in a bittersweet mood as I read the reports about the death of the European Space Agency’s Rosetta comet probe. Its demise was carefully planned and long foretold but was sad all the same, putting a period at the end of a story that rolling out for more than 12 years. During that time, Rosetta made three passes by Earth, one by Mars, visited a pair of asteroids, and spent more than two years scrutinizing Comet 67P/Churyumov–Gerasimenko (typically shorted to “Comet 67P” for obvious reasons). It was the first spacecraft to orbit a comet. It also deployed the first-ever comet lander, Philae.
Now all that is over. No way around it, the end of a great adventure is bitter.
The sweet part is the extraordinary science Rosetta has conducted along the way. Early results confirmed the presence of diverse organic compounds; showed that comets alone could not have provided the water that fills Earth’s oceans; mapped the surprisingly complex magnetic environment around Comet 67P; and catalogued enormous eruptions of gas and dust–roughly 100,000 kilos [200,000 pounds] at a time–that show how comets disintegrate under the force of solar heat. Much of Rosetta’s dataset has yet to be fully analyzed. Planetary scientists will be mining new insights from it for many years to come.
Sometimes it takes a while for the meaning of a new scientific discovery to really sink in. In the case of the planet Proxima Centauri b, announced last week, it may take decades or even centuries to fully grasp the importance of what we have found. You see, this is not just any planet: It is similar to Earth in mass, and it orbits its star in the “habitable zone,” where temperatures could potentially allow the existence of Earthlike bodies of liquid water. Proxima Centauri is not just any star, either: It is the very nearest one after the Sun, and it is a small red orb whose feeble light makes it relatively easy to study the planet close beside it.
The science at stake here is enormous. Proxima Centauri b will surely become the archetype for understanding more distant Earth-size, and possibly Earth-like, planets all across our galaxy. The effort needed to study it will be enormous, too, however. At present the planet cannot even be glimpsed directly through the mightiest telescopes on Earth. Nevertheless, the race is on–a thrilling but maddeningly slow-motion race to bring Proxima Centauri into view, to figure out if it could (or does!) support life, even to visit it with an interstellar probe.
If you look in enough places, eventually you’ll find something profoundly strange. That’s been a reliable rule of thumb through the history of science, and last year it proved dramatically true again for astronomer Tabetha Boyajian. While digging through data from NASA’s Kepler space telescope, which has been monitoring 150,000 stars for signs of orbiting planets, she realized that one of these things is not like the others. A single star in that set, formally catalogued as KIC 8462852 but informally known as Tabby’s Star, flickers in an inexplicable way: unlike the shadows produced by planets, unlike any known type of stellar pulsation, simply unlike anything seen before.
Tabby’s Star is so unusual that a few scientists, including Boyajian’s colleague Jason Wright, raised the possibility that its flickering is not natural but is due to the presence of an enormous artificial construct. That speculation quickly lent KIC 8462852 another nickname, the “alien megastructure star,” and prompted a flood of breathless news stories; it even got a shout out on Saturday Night Live. Boyajian’s subsequent TED lecture drew even more attention to her star. [Update: A week after I posted this interview, Tabby’s Star star got weirder still: A new study shows that it has been inexplicably getting dimmer over the past three years.]
If you are looking for cerebral science fiction stories that meticulously explore the outer limits of known science, Roland Emmerich is not your guy. The auteur behind the 1996 alien-invasion movie Independence Day and its new sequel, Independence Day: Resurgence, is all about spectacle over subtlety. (2012 and The Day After Tomorrow are also his handiwork.) Blowing up cities? Check. Sciencing the sh*t out of things? Not so much.
Taken on its own terms, though, the first Independence Day was a lot of fun and—beneath the popcorn-chewing action—smarter than it looked. Emmerich’s best idea was not trying to give his aliens convoluted, ludicrous motivations. Instead he envisioned them as a rapacious swarm, roaming instinctively from planet to planet in search of resources. The sequel maintains that premise and supersizes it, in the inevitable Hollywood style.
First of all, let me reassure you that this post has nothing at all to do with Donald Trump. The billionaire in question is not the presidential candidate but Nathan Myhrvold, the former chief technology officer at Microsoft. The doomsday I’m talking about is not political but physical. And the dust-up comes down to a contentious but ultimately quantifiable issue: What is the real risk from asteroid impacts?
In a recent paper, Myhrvold charges that NASA scientists have made some serious errors in calculating the size and properties of the asteroids that come dangerously close to our planet. The specific details are fairly technical (you can read a semi-popular summary of his argument here in PDF form), but the upshot is plain enough. If the estimated asteroid sizes are wrong, so are the associated dangers posed by these objects. That would raise a whole new level of uncertainty around a type of natural disaster that is already the subject of highly polarized hype and dismissals.
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).