Friday Review

Spotting the look-alikes

Sara Seager

Sara Seager   | Photo Credit: 28dfr Sara Seager1

Sara Seager’s discussion on search for life in the universe makes us wonder if we are alone

When you listen to Sara Seager talk on the search for planets beyond our solar system, you get goose pimples. Are we really not alone? How big is the Universe? Well, if you had all the answers, I guess it would not be so exciting but as the tapestry peels off bit by bit, and you draw your own conclusions about the world beyond of beyond, even wonder throws up its hands to limitlessness.

Says Seager, professor at the Massachusetts Institute of Technology and known for her work on extrasolar planets and their atmospheres, “Every star in our sky is a sun. And if our sun has planets …surely those other stars should have planets also, and they do. And in the last two decades, astronomers have found thousands of exoplanets.” Exoplanets by the way, means a planet that orbits a star other than the sun. Seager continues, “Our night sky is literally teeming with exoplanets. We know, statistically speaking, that every star has at least one planet… Is there life out there? Who is out there? …I'm here to tell you just how close we’re getting to finding out the answer to this question. It's the first time in human history that this really is within reach for us…I think of the fact that our sun is but one of many stars. Our Milky Way is a collection of bound stars. But our sun is one of hundreds of billions of stars and our galaxy is one of upwards of hundreds of billions of galaxies. Knowing that small planets are very common, you can just do the math. And there are just so many stars and so many planets out there, that surely, there must be life somewhere out there…”

How does she say that? Seager mentions a few of them,”Kepler-186f… a system of about five planets. This planet is in a zone that is not too far from the star, so that the temperature may be just right for life…It orbits a red star, and we're just speculating that if there is vegetation that does photosynthesis, it has different pigments and looks red.” HD 40307g, a Super-Earth because it is much bigger than the earth and has much greater surface gravity, Kepler 16b, a planet that orbits two suns, so you literally have two shadows, Kepler-10b, a hot, hot planet that orbits over 50 times closer to its star than our Earth does to our sun, Gliese 1214b which is somewhat warm has lower density is probably a water world…

To know if there is life anywhere else Seager says we have to study the atmosphere of the planets and that may be indicative. “…our own Earth has oxygen in the atmosphere to 20 per cent by volume. That's a lot of oxygen. But without plants and photosynthetic life, there would be no oxygen… So oxygen is here because of life….”

So to look for oxygen alone, is not indicative in itself. What we need to know is the composition of the other gases in the atmosphere of the exoplanets…but then there are so many gases! So Seager says she and her team have, “… developed star shade so it blocks out the light of a star so that the telescope can see the planets directly.” When that star shade does fly off, Seager says, “I can guarantee that in the next generation of space telescopes, we will have the capability to find and identify other Earths. And the capability to split up the starlight so that we can look for gases and assess the greenhouse gases in the atmosphere, estimate the surface temperature, and look for signs of life. But there’s more. In this case of searching for other planets like Earth, we are making a new kind of map of the nearby stars and of the planets orbiting them, including planets that actually might be inhabitable by humans. And so I envision that our descendants, hundreds of years from now, will embark on an interstellar journey to other worlds. And they will look back at all of us as the generation who first found the Earth-like worlds.”

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Printable version | May 29, 2020 3:11:41 AM |

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