Ask Ethan: What Will Our First Direct Image Of An Earth-Like Exoplanet Look Like?
“[W]hat kind of resolution can we expect? [A] few pixels only or some features visible?”
I’ve got good news and bad news. With the next generation of space-based and ground-based telescopes on the way, we’ll finally be able to image Earth-sized and super-Earth-sized planets around the nearest stars to us directly. Unfortunately, even the largest of these telescopes won’t be able to resolve these planets beyond being a single pixel (with light leaking into the adjacent pixels) in angular size. But even with that limitation, we should be able to recover signatures of continents, oceans, icecaps, clouds, atmospheric contents, water, and potentially even life.
Come find out what we will (and won’t) be able to do with our first direct images of Earth-sized exoplanets, coming to you in just a few years!
Ask Ethan: Would Life On Earth Be Possible If We Were Anyplace Else In The Galaxy?
“[W]hat would happen if our solar system had formed a little farther up the arm of the galaxy? What would happen if we were at the tip of the arm? What if, theoretically, instead of the humongous black hole in the center of our galaxy, our solar system was there? Would there be major climate difference[s]? Would we be able to survive?”
We can all agree that what’s happened here on Earth is something that’s extremely special in the Universe. Our planet has developed and sustained life on it for over four billion years, and that life continues to thrive even at present. Our planet has been fortunate enough to have stable enough conditions and mass extinction events that have never eliminated 100% of the life that exists on our world. But how ‘special’ does that make Earth, that this is our story? Do we need a large Moon? A solar system like ours? A star like our Sun? And do we need to be located at our present location in the galaxy, or would many places be just as good?
It’s a tough question to answer with certainty given the paltry evidence we have, but we can certainly examine these questions in-depth. Let’s do exactly that for this edition of Ask Ethan!
Humanity’s 3 Hopes For Finding Alien Life
“Although it’s just conjecture at this point, scientists speculate that life in the Universe is probably common, with the ingredients and opportunities for it to arise appearing practically everywhere. Life that thrives and sustains itself on a world, to the point where it can change its atmospheric and/or surface properties, may need to get lucky, and is likely more uncommon. Evolving to become complex, differentiated, multicellular creatures is likely even rarer. And as far as becoming what we would consider an intelligent, technologically advanced civilization, it could be so exceedingly remarkable that in all the Universe, it might just be us. Yet despite how different these outcomes are, we’re actively searching for all three types of life in very different ways. When the first sign of alien life finally is discovered, which one shall emerge victorious?
No matter which method pays dividends first, it will be among the greatest day in the history of life on Earth.”
There are three very different ways humanity is searching for alien life beyond Earth. We can directly search the various planets and moons in our Solar System for past or present biological signatures simply by sending decontaminated probes, and looking for the evidence in situ. We can indirectly look at distant worlds around other stars, searching for the characteristic changes to the atmosphere and surface that life would bring. And, most optimistically, we can search for intelligent signatures created, perhaps willfully, by a technologically advanced alien species.
These are our three hopes for finding alien life, and we’re actively pursuing all three. Which one, if any, do you think has the best chance of paying off?
NASA Kepler’s Scientists Are Doing What Seems Impossible: Turning Pixels Into Planets
“It isn’t the image itself that gives you this information, but rather how the light from image changes over time, both relative to all the other stars and relative to itself. The other stars out there in our galaxy have sunspots, planets, and rich solar systems all their own. As Kepler heads towards its final retirement and prepares to be replaced by TESS, take a moment to reflect on just how it’s revolutionized our view of the Universe. Never before has such a small amount of information taught us so much.”
When you think about exoplanets, or planets around stars other than the Sun, you probably visualize them like we do our own Solar System. Yet direct images of these worlds are exceedingly rare, with less than 1% of the detected exoplanets having any sort of visual confirmation. The way most planets have been found has been from the Kepler spacecraft, which gives you the very, very unimpressive image of the star you see featured at the top. Yet just by watching that star, the light coming from it, and the rest of the field-of-view over time, we can infer the existence of sunspots, flares, and periodic “dips” in brightness that correspond to the presence of a planet. In fact, we can figure out the radius, orbital period, and sometimes even the mass of the planet, too, all from this single point of light.
How do we do it? There’s an incredible science in turning pixels into planets, and that’s what made NASA’s Kepler mission so successful!
Despite Roasting Flares From Its Sun, Proxima b Might Still Have Life
“It’s true that stars that are very different from our Sun have restrictions on what conditions their planets can have and still be habitable. For red dwarf stars like Proxima Centauri, their worlds have conditions that make it unlikely for life to have taken the exact same evolutionary pathway that life on Earth took. But that doesn’t spell doom for life; it merely indicates that alternative pathways are required to arrive at similar outcomes. Frequent flares and excessive blasts of ultraviolet radiation may spell doom if Earth-based life were subject to those conditions, but organisms that have adapted to their environments could survive these outbursts routinely. A few solar hiccups a year should pose no problem for life forms that developed under those exact. harsh conditions. On every world, after all, it should be the organisms most robust against the adversarial conditions they face that will survive.”
The nearest star to us, Proxima Centauri, was discovered to have an Earth-sized planet in its habitable zone just two years ago. In that time, scientists have observed catastrophic flares comfing from the red dwarf star, fearing for the survival of any life on the planets orbiting it. Many now claim that planets orbiting red dwarfs are completely inhospitable to life, since the combination of tidal locking, ultraviolet-rich flares, ozone depletion, and a lack of higher-energy light in general would make photosynthesis and life-as-we-know-it an impossibility. How narrow-minded of us to go down that road! In reality, the energy source is there, the conditions are right for liquid water, the atmosphere as a whole will stick around, and there are many, many adaptations that could lead to life not only surviving, but thriving on a world like Proxima b.
It’s easy to look at a world that’s different from ours and declare how life like ours wouldn’t do well, but the key is to figure out what kind of life would do well there. That’s where the greatest chances for success are. That’s where we need to look.
Sorry, Super-Earth Fans, There Are Only Three Classes Of Planet
“What’s really interesting is how the mass/radius relationship changes for these three different classes of world. Up to about double the Earth’s mass, or a size just ~25% larger than Earth’s radius, you have an opportunity to be Earth-like, with thriving life on the surface. Beyond that, you’ll have an enormous hydrogen/helium envelope, and be much more akin to Neptune, Uranus or Saturn. In other words, what we’ve been classifying as “super-Earths” aren’t anything like Earth at all, but are instead gas giant worlds, expected to be wholly inhospitable to life on their surfaces.”
Thanks to NASA’s Kepler mission, we’ve discovered literally thousands of worlds that lie beyond our own Solar System. Surprisingly, the majority of them aren’t like anything we have in our own backyard, but are somewhere in between Earth and Neptune in terms of size and mass. These worlds, usually broken into categories like “super-Earths” and/or “mini-Neptunes,” have often been viewed as new categories of planets, along with the “super-Jupiters” that we don’t see here, either. Yet these classifications are purely arbitrary, based on what we’ve seen and how we classified planets in our own neighborhood. What would we get if we classified them based on the properties that they actually possess, like mass and radius? We’d find, quite surprisingly, that there are only three classes of planet: Terran, Neptunian, and Jovian-like worlds.
Moreover, practically everything we’ve been calling a super-Earth isn’t Earth-like at all, but a Neptunian world. Come get the full story on the planets that exist in our Universe!
Do Earth-Sized Planets Around Other Stars Have Atmospheres? James Webb Will Find Out!
“Even so, because of its ability to measure light to high sensitivity far into the infrared, there’s a remarkable hope for determining whether these worlds have atmosphere regardless of any other measurements. As planets orbit their star, we see different phases: a full phase when it’s on the far side of the star; a new phase when it’s on the near side, and everything in between. Based on the temperature of the world at night, we’ll receive different amounts of infrared light from the "dark” side that faces away from the Sun. Even without a transit, James Webb should be able to measure this.“
The overwhelming majority of Earth-sized, potentially habitable planets that Kepler found are in orbit around red dwarf stars. In many ways, this is great: red dwarf stars are stable, temperature-wise, for longer than our Sun. Their planets are easier to detect, and they will be the first Earth-sized ones we can measure the atmospheres of directly. But even if we can’t make those measurements with James Webb, we’ll be able to learn whether they have atmospheres or not via a different method: by measuring the infrared radiation coming from the planets themselves in various phases. Just as we can measure the presence of Venus’ atmosphere from the hot, infrared radiation emanating from it even on the night side, we can make those same measurements with James Webb of other Solar Systems. By time the early 2020s roll around, we’ll have our first answers to this longstanding debate.
Many scientists think that Earth-sized planets around M-class stars will have no atmospheres left; others think there’s a chance they survive. Here’s how James Webb will find out!
How Shooting For Alpha Centauri Will Change The World
“To construct such a laser array would necessitate a tremendous investment in the building of infrastructure in space. To develop the sails capable of reflecting enough light while withstanding the heat and maintaining their balance will require a tremendous advance in materials science and engineering. To withstand the journey through interstellar space at such high speeds, we’ll need to develop unprecedented shielding/deflection technologies. To slow down to sufficiently low speeds to take data will require a new kind of braking technology, which will likely also be developed in tandem with the laser sail. And to miniaturize the technologies capable of storing, recording, and transmitting information from the Alpha Centauri system back to Earth will likely mean we need to reach (or at least approach) the quantum limit for materials.”
If you want to accomplish something great, you need to be willing to take on challenges that might seem impossible, given what we currently know. But striving for those lofty goals, and investing the necessary resources in the endeavor, is how we move forward as a species. If we aim for Alpha Centauri, there are a huge number of challenges and obstacles we’ll have to overcome, but none of them require overhauling the laws of physics. Instead, they simply require developing new techniques and technologies, which is the same set of challenges that the Apollo program faced. When we look at the spinoff technologies that have traditionally come from this type of research and development, we find that the value we’ve gleaned has far surpassed whatever we invested. Imagine what will be come possible if we develop what we perceive is necessary for a reconnaissance mission to another star system?
Even if the mission itself fails, simply attempting to reach for the stars could change our world in ways we can barely envision. It’s worth it. Let’s go.
Why NASA’s Kepler Mission Is Toast
“It was a great mission. The scientists working to extract the last usable pieces of data — both on an ongoing basis from K2 and from the archival data of the original mission — are honestly doing great work. But if you think Kepler-90 is anything like our Solar System, or has eight planets like ours does, you’ve fallen for the NASA hype train.”
We’ve found the very first planetary system out there, beyond our own, with 8 planets in it. At least, that’s what the announcements would have you believe, and it’s kind of true: there are _at least_ 8 planets orbiting Kepler-90. But there are probably many more, and what we’re seeing isn’t reflective of all that’s there, but simply of the limits of the Kepler mission’s data. To go beyond what Kepler has seen, we’ll need better observatories, and that requires both more funding and additional patience. The latest advance was a minuscule drop-in-the-bucket, and rather than teaching us anything about our Solar System, it’s instead teaching us about the absolute limits of what’s possible with all the data NASA’s Kepler mission has ever taken.
It’s time for something better, if we want a real advance in the science of exoplanets. Find out why in this thinkpiece that goes way beyond what everyone else is reporting!
Ask Ethan: How Many Planets Did NASA’s Kepler Miss?
“Since Kepler uses the transit method to detect exoplanets, how many are we missing due to non-ecliptic alignment?”
With a field-of-view encompassing 150,000 stars, NASA’s Kepler mission delivered an overwhelming prize when it came to hunting worlds beyond our own Solar System: thousands of new exoplanets. The majority of them, however, were different from what we have at home. They were larger, more massive, closer to their parent stars, and orbiting more quickly than what we find in our own neighborhood. In other words, we found the worlds that were easiest to find. But NASA’s Kepler wasn’t sensitive to all the worlds that were out there. Sure, to observe a transit, where a planet passes in between its parent star and ourselves, requires a fortuitous alignment, and we can certainly extrapolate how many more exoplanets like the ones we’ve already seen are out there. But to know how many planets NASA’s Kepler mission truly missed requires a whole slew of other information, much of which the Universe hasn’t yet revealed to us given our current technology.
How many planets are actually out there in our galaxy? And how are we going to find out the true number? Get the answer on this week’s Ask Ethan!