Astronomers Confirm Discovery of Youngest Known Exoplanet

Jun 24, 2019

Astronomers have found more than four thousand “extrasolar planets” beyond our solar system. Now a team including scientists at Flagstaff’s Lowell Observatory have confirmed the discovery of the youngest known extrasolar planet. It’s a scorching-hot world many times larger than Jupiter. KNAU’s Melissa Sevigny spoke with Lowell astronomer Lisa Prato about how this finding informs our understanding of how planets form.

Artist's concept of planets around a young star
Credit NASA/JPL-Caltech/T.Pyle

Going into this project, what was the question you wanted to answer?

So this project began in 2004. There were lots of old planets that had been discovered, which is pretty exciting. But we realized nobody knew how they formed. There were lots of theories, there were lots of models, but nobody had been finding young planets. For me, young is 1 million, 2 million, 5 million years old. That is like the first seconds in the span of a human’s life, relative to the span of a star’s life.   

Tell me about the planet you looked at for this project. What do we know about it?

It took us 10 years of work observing at 5 different telescopes. We were looking for evidence that very young stars were wobbling back and forth because they had a newly formed planet around them… Young stars are—think about babies having tantrums, really, really bad tantrums. That’s what happens with a young star: it has huge spots that cover half the surface, it has gigantic flares hundreds of thousands of times stronger than those on the sun, it has prominences, winds. They’re wicked places, and they’re very variable when you look at them with astronomical equipment and telescopes. It takes a lot of effort and a lot of time to pull out this very subtle signal of a planet tugging the star back and forth. At first we didn’t see the planet itself, we just saw the impact on the star. But we were pretty certain. So we published the initial identification, the indirect evidence in 2016, that showed a massive planet around CI Tau.

So what can you find out about a planet like that, that’s so far away? You know it’s there, what kind of information can you get out of that light coming back?

When we published in 2016, we could see how much how the star was moving, and how fast it was moving back and forth. That told us the orbital period of the planet, which is 9 days, so this planet is very close in to that star, it’s whipping around really fast.  But the real icing on the cake that we just announced was that we can see the planet directly. We were able to do that using the Discovery Channel Telescope. You can actually see carbon monoxide in the atmosphere of the planet. That tells us exactly what the mass of the planet is, it’s about 11 times more massive than Jupiter, and it tells us exactly how bright it is, and it’s very bright. That tells us something about which models for planet formation may actually be correct… All of those things will go into these models and improve them, and we just keeping looking for more young planets.

Has that ever been done before, direct observation of an exoplanet?

That has been done before, but this is the very first time this technique has been applied to a young planet. It’s huge. For the field of planet formation, this is a very significant confirmation…. I think part of what this means is that planets start to form much earlier than we thought we did…. Of course there’s always more and more to answer. The more you find out, the questions you have, hopefully. You’re always seeking more knowledge and more information simply because of a hunger to understand and a curiosity that doesn’t let you sleep.

Thank you so much for speaking with me, I appreciate it.

Sure thing.