Is there life beyond our solar system? │ 5-Minute Science You Never Knew with Dominic Bowman

ZOEY

Hi, Dominic great to have you again! So, this time you are going to tell us about how scientists are searching for the aliens out there in the universe.

DOMINIC

Yes, that's right. Thanks for having me again. I'm very happy to discuss our ongoing search

for what we call exoplanets. These are planets beyond our own solar system, and whether they contain alien life. So here on planet earth, life comes in many different shapes and sizes, from the smallest bacteria to the largest plants and animals. But in this long list of known living organisms here on earth all of them have something in common. They require water to maintain their biology.

Since more than two-thirds of the earth's surface is covered by oceans small rocky planets with large oceans beyond our solar system are very good places to search for alien life. To have a chance of finding aliens, maybe bacteria or even plants and animals like us on exoplanets, astronomers need to find small rocky planets with large quantities of liquid water.

ZOEY

So how do these scientists find their expert planets at first place Dominic?

DOMINIC

Well, there are a few different ways of doing this but one of the most successful is called the transit method. Imagine looking through a telescope and you're looking at a star if anything passes in front of that star like a planet it will block out some of the Starlight, and this in astronomy is called a transit. The bigger the planet the more Starlight it will block. If astronomers use telescopes to measure the light from a star over a long period of time and make what we call a light curve, astronomers can spot these transits and measure the size of the planet.

Once the planet has revolved around the star in a circle and got back to where it started again it will block out some of the Starlight once again, and this allows astronomers to measure the planet’s orbital period. That means how long it takes for the planet to go around the star and it's what it we call a year here on earth.

ZOEY

Wow. How many planets have we detected so far using the method?

DOMINIC

Well, as of today it's about 6,000 which is quite a large number with most of these extra planets being discovered using the transit method, with space telescopes like NASA's Kepler and test space telescopes. Once the planet is detected we can use some of the largest telescopes here on earth to measure the mass from the relative motion of the planet and the star orbiting each other. This is what we call the radial velocity method in astronomy, and it requires us to split the star's light into its component colours what we call a spectrum.

When the distant star is moving towards us relative to the planet, the spectrum gets a little bit of a boost and when the star is moving away from us relative the planet it gets a little bit of a drag and the size of this effect allows astronomers to measure the planet's mass because since more massive planets have a bigger influence on their star.

It's quite similar to when you an ambulance is traveling towards you its siren has a higher frequency but once it's moved past you and now traveling away from you its siren sounds lower. It has a lower frequency.

Using the transit detections from space telescopes and the radial velocity measurements of the planets from the ground astronomers have found some really interesting exoplanet systems, including some planets that have two stars instead of one.

ZOEY

Okay. So, so far have you found any signs of alien life yet?

DOMINIC

Well, the jury's still out. So not quite yet, but in the future there will be the next generation of space telescopes that are specifically designed to measure the chemistry of the atmospheres of these exoplanets and directly detect whether their atmospheres contain the signatures of life such as the water or the carbon dioxide that living organisms breathe. So, there is still quite a lot more work to do but the future is very exciting for exoplanets.

ZOEY

Great! So, we have come to almost an end of our conversation for today, any final messages?

DOMINIC

Yes, absolutely. There is always a very good chance of finding alien life on exoplanets in the Universe because there are so many planets out there. Based on current results, astronomers predict that almost all of the stars in our Milky Way galaxy have on average at least one planet. That means our chances of finding planets very similar to Earth with possible alien life is not so bad at all.

ZOEY

Thank you so much Dominic and great to have you again I hope to see you soon next time and thank you so much for the fans out there

DOMINIC

Bye bye, thanks for having me.