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| Warning: Lots of technical jargon ahead. Links have been provided when deemed appropriate. |
If there is a list of people who are SUPER excited about space exploration, then I am definitely on it. Potential water geysers on Enceladus and Europa? Awesome! The Opportunity rover still exploring Mars? Excellent! Voyager 1 sending data back from beyond the heliopause? Rock on! James Webb Telescope to launch within the next two years!!! Can't wait!!! Potential water AND life on Proxima b!!! Wait? What!?!? Let's not get ahead of ourselves here...
Without putting too much of a damper on the potential for life on Proxima b, we must be careful to distinguish facts from speculation. There are a number of factors which we believe were important to the development of life on our planet, and Proxima b does share some of those features. It is a rocky planet, which significantly increases the likelihood of molecular water, as well as the basic elements necessary to form life. Also, it is within the Goldilocks Zone, which allows for the potential of liquid water on the surface. And... well... that's about it for the potential-to-support-life column. We really don't know much about this planet yet, and we don't know nearly enough about it to say whether it has water, much less life on it. In fact, it could be decades before we know if there's even water on it. And this is the closest possible extrasolar planet we will be able to study, ever!
Also, what we do know about Proxima b makes it a very different world from Earth. The planet is approximately 30% larger than the Earth. Its star, Proxima Centauri, is much cooler than our own - 3000 K at the surface, compared to 5800 K. The planet is much, much closer to Proxima Centauri than we are to the sun. In fact, it is seven times closer to Proxima Centauri than Mercury is to the Sun! Because it is so close to the star, Proxima b orbits very quickly, with a solar year being approximately 11.2 days, compared to 365 for Earth. Just having these few fundamental pieces of data gives us an interesting picture of this tantalizingly close exoplanet, and it doesn't look much like Earth at all. Let's consider what the reality is on Proxima b.
What would our eyes perceive if we were on Proxima b? To answer that, we need to understand some things about what our eyes actually detect. The Sun, and just about everything else, produces energy all along the electromagnetic spectrum. This energy ranges from gamma rays to x-rays, ultraviolet waves, radio waves and more. However, only some of the Sun's energy reaches Earth. And a lot of that energy gets absorbed once it hits that dense gas of the atmosphere surrounding our little planet. There are only a few "pockets" of wavelengths that actually make it to the ground. One of those "pockets' is the range we call the visible spectrum, for obvious reasons. Everything you see is due to these particular wavelengths of light making it from the Sun, through our atmosphere, and to our eyes.
As noted above, Proxima Centauri is much cooler than the Sun. Which means that its energy output is quite different. If fact, its peak output is predominately in the infrared range. Based on surface temperature, we know that there is very little energy in the visible spectrum coming from it. Despite the planet being twenty times closer to Proxima Centauri than we are to the Sun, the star would only be a dim red circle to our eyes. Visually, it would be approximately five times the size of the sun, but it would be so dim that you could stare right at it without hurting your eyes. In fact, it would even be significantly dimmer than a full moon on Earth! And it would be very, very red. This, of course, is presuming that the atmosphere even lets in energy at visible wavelengths. It might not. For us, the "dim red disk" is a best case scenario. It could be totally dark.
No Earth plants would grow on Proxima b without artificial sunlight, even if there was liquid water. Plants rely on the visible spectrum, too. They use photosynthesis to absorb certain wavelengths of visible light and covert it to energy, and they simply would not get enough of that light on Proxima b to survive. In addition, being so close to the star means that the impact of solar flares and coronal mass ejections is likely to be much more intense. These solar outbursts release significant amounts of gamma- and x-ray energy, which is detrimental to life as we know it. Finally, there's a good chance that the planet is tidally locked to the star, because it is so close to it. This is the situation the moon is in with Earth, which is why we only ever see one side of it. If this is the case, then half of the planet would always have a dim red disc high in the sky above, and the other side would eternally stare out into the vastness of space. So one side could be warm, but very dangerous, and the other could be much safer, but cold and dark. When Proxima b is described as Earth-like, the reference is essentially regarding the mass and elemental makeup of the planet, and has very little relation to the things which a typical person would imagine - sunshine, clouds, plants, seasons, etc.
Now all of this seems like an epic bummer, but it's really not. It's simply the reality of what we know. So, rather than jumping to wild speculations such as "there might be liquid water" or "there could be life" on Proxima b, we should consider what it really means to have an exoplanet orbiting the nearest star to us. First of all, it supports what we've suspected for a number of years now, most stars have planets. This means that there will be thousands of future planets for us to study, and many of them will be more similar to Earth than Proxima b. Next, we have an excellent specimen upon which we can test our future equipment and theories. For example, did you know that we can't even see Proxima b? We just know that it's there because of a fluctuation in the radial velocity, or, more simply, a "wobble" detected from Proxima Centauri. In fact, most planets which could qualify as second Earths are nearly impossible to detect with our current technology. Now, some would be discouraged by that, but not astronomers!
Astronomers, and all scientist really, love the unknowns. You can be assured that astronomers are already wracking their brains to figure out ways of learn more about our intriguing neighbor. Perhaps some of the new telescopes will help us detect interactions between the magnetic fields of the star and the planet. Or maybe after the James Webb telescope is launched in 2018 we'll have enough resolving power to detect an atmosphere around Proxima b. It's possible there is a way to capture and analyze the light and motion we can already detect which will give us more information about our neighbor. The great thing about science is that it looks for the possibilities, and then chases after the facts. More often than not, it's what we don't know that gets the scientific community excited. And there's so much we don't know about Proxima b!
Could there be life on Proxima b? Sure, there could be. But the reality is that we haven't confirmed life on any of the other bodies in our own solar system. Let's continue to work on that for now, since bodies in our solar system are about 60,000 times closer than Proxima b, and are much more likely to yield results in the next 100 years. There are a lot more things we can focus on with Proxima b right now. Things which will help to advance our understanding of the universe as a whole. It is exciting, and perhaps terrifying, to consider that we may discover life outside of Earth within the span of our own lives. But, the reality is that Proxima b is not going to be where we find it first. Let's figure out how much we can learn about Proxima b in the next 20 years. In the meantime, let's also search for life on Europa, Enceladus and Mars, since we can actually physically get to them. It just makes better sense.
There is science. And then there is science fiction. Let's do our best to make the distinction between the two. Speculation is great. Getting the public excited about science is awesome. We just need to be careful about the expectations that are set by speculation. False expectations lead to disappointment, and disappointment can be the death of scientific research. To me at least, the facts are even more exciting than the possibilities. Let's not let wild conjecture interfere with good research. The answers are out there, and we will find them. Give it time, folks!
No Earth plants would grow on Proxima b without artificial sunlight, even if there was liquid water. Plants rely on the visible spectrum, too. They use photosynthesis to absorb certain wavelengths of visible light and covert it to energy, and they simply would not get enough of that light on Proxima b to survive. In addition, being so close to the star means that the impact of solar flares and coronal mass ejections is likely to be much more intense. These solar outbursts release significant amounts of gamma- and x-ray energy, which is detrimental to life as we know it. Finally, there's a good chance that the planet is tidally locked to the star, because it is so close to it. This is the situation the moon is in with Earth, which is why we only ever see one side of it. If this is the case, then half of the planet would always have a dim red disc high in the sky above, and the other side would eternally stare out into the vastness of space. So one side could be warm, but very dangerous, and the other could be much safer, but cold and dark. When Proxima b is described as Earth-like, the reference is essentially regarding the mass and elemental makeup of the planet, and has very little relation to the things which a typical person would imagine - sunshine, clouds, plants, seasons, etc.
Now all of this seems like an epic bummer, but it's really not. It's simply the reality of what we know. So, rather than jumping to wild speculations such as "there might be liquid water" or "there could be life" on Proxima b, we should consider what it really means to have an exoplanet orbiting the nearest star to us. First of all, it supports what we've suspected for a number of years now, most stars have planets. This means that there will be thousands of future planets for us to study, and many of them will be more similar to Earth than Proxima b. Next, we have an excellent specimen upon which we can test our future equipment and theories. For example, did you know that we can't even see Proxima b? We just know that it's there because of a fluctuation in the radial velocity, or, more simply, a "wobble" detected from Proxima Centauri. In fact, most planets which could qualify as second Earths are nearly impossible to detect with our current technology. Now, some would be discouraged by that, but not astronomers!
Astronomers, and all scientist really, love the unknowns. You can be assured that astronomers are already wracking their brains to figure out ways of learn more about our intriguing neighbor. Perhaps some of the new telescopes will help us detect interactions between the magnetic fields of the star and the planet. Or maybe after the James Webb telescope is launched in 2018 we'll have enough resolving power to detect an atmosphere around Proxima b. It's possible there is a way to capture and analyze the light and motion we can already detect which will give us more information about our neighbor. The great thing about science is that it looks for the possibilities, and then chases after the facts. More often than not, it's what we don't know that gets the scientific community excited. And there's so much we don't know about Proxima b!
Could there be life on Proxima b? Sure, there could be. But the reality is that we haven't confirmed life on any of the other bodies in our own solar system. Let's continue to work on that for now, since bodies in our solar system are about 60,000 times closer than Proxima b, and are much more likely to yield results in the next 100 years. There are a lot more things we can focus on with Proxima b right now. Things which will help to advance our understanding of the universe as a whole. It is exciting, and perhaps terrifying, to consider that we may discover life outside of Earth within the span of our own lives. But, the reality is that Proxima b is not going to be where we find it first. Let's figure out how much we can learn about Proxima b in the next 20 years. In the meantime, let's also search for life on Europa, Enceladus and Mars, since we can actually physically get to them. It just makes better sense.
There is science. And then there is science fiction. Let's do our best to make the distinction between the two. Speculation is great. Getting the public excited about science is awesome. We just need to be careful about the expectations that are set by speculation. False expectations lead to disappointment, and disappointment can be the death of scientific research. To me at least, the facts are even more exciting than the possibilities. Let's not let wild conjecture interfere with good research. The answers are out there, and we will find them. Give it time, folks!
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