Could another planet Earth exist?

Is there another rocky planet like ours out in the universe?
07 December 2021


The four rocky planets, imaged side by side



How do we analyse objects like asteroids and planets that are so far away from us?


Julia Ravey spoke to Hannah Wakeford from the University of Bristol who researches planets outside our solar system about how it is possible to get up close with objects so far away...

Hannah - That's a really good question and it's not easy, but what we're doing is we're looking for light. That's what astronomy is, we always are just dealing with light around things. We're seeing the reflections of light from the sun off those asteroids, or we're seeing the light that they emit themselves. Another thing that's good about these asteroids is because they're so close to us, they move really quickly, and because they're moving really quickly, we can see that there's something moving relative to the stars, which appear static in our pictures. If we can see this little bit of light moving through our pictures, that might be an asteroid.

Julia - And what types of planets do you study?

Hannah - I primarily study giant planets. These are things that are made mostly of hydrogen and helium. They don't have a surface that you would think of. They're very, very puffy. And the ones that I particularly am interested in are the ones that are really close to their stars. So they're hot as well. When you heat up an atmosphere you change the chemistry, you change the wind structure, and you change the way that that planet orbits around its star. There's a lot of interesting things that we're trying to understand. How big of a difference does that make?

Julia - And that type of planet doesn't sound like one that we could maybe move to many years down the line. Do you think that could be another Earth out there?

Hannah - We've been looking across the whole sky for exoplanets and we found nearly 5,000 of them that have been confirmed as real planets orbiting other stars. Out of those planets, we think that there are hundreds and thousands of planets that are rocky terrestrial worlds. We know that there are rocky planets the same size as the earth and we know that before we even started looking for exoplanets because we have one next door to us, it's called Venus. It is our twin sister planet. It is the same size and mass as the earth and it is a rocky planet. So we already knew that planets like ours were out there, but the important thing here is those little differences. We live on this lovely planet called Earth and it is pretty nice, good temperatures, a little bit cold in the UK today. But Venus is a hellish world; It has an incredibly thick atmosphere, the temperatures on the surface are 700 degrees, you would melt and be crushed. It's a horrible place, but they're rocky planets that are roughly the same size. What we're trying to understand about exoplanets is what are those little differences? If we find a rocky planet that is about the size of the earth, is that really an Earth-like planet?


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