Q&A with UNC astronomy professor on the discovery of 7 new planets — potentially with life

Seven Earth-size planets with temperatures that could support life were discovered 235 trillion miles from Earth, orbiting a dwarf star named TRAPPIST-1. Nicholas Law, a professor in the Department of Physics and Astronomy, discussed the findings with senior writer Olivia Slagle.

The Daily Tar Heel: In layman’s terms, what was discovered?

Nicholas Law: So this is a discovery from the Belgian survey, which has a set of small telescopes, which are looking at very cool, small stars. What they do is they stare at those stars for a long time and wait to see if a planet in those stars’ solar systems passes in front of that star.

So if a planet passes in front of the star it blocks a little bit of light from the star and the star becomes a bit dimmer, and we can see that decrease in brightness as an indication that there is a planet there.

DTH: Why is the discovery important?

NL: What this comes down to is that we would really like to know how common life is in the universe. And this discovery shows a solar system with three or four worlds in it, all of which’s temperatures are at the range where water could be on their surfaces. The type of star this is the most common type of star in our galaxy.

What this tells us is there are millions of planets like this or even billions of planets like this in our galaxy alone, which suggests that it is very unlikely that we are alone, if there are this many Earth-like planets out there.

DTH: How much has our understanding of the universe changed in recent years?

NL: In particular, in planets, five years ago we had absolutely no idea how many worlds like the Earth there are out there. And with the launch of the Kepler space telescope we found dozens of planets, which are at least the same size as the earth, so rocky planets, that were distances from their stars where the temperature would be good enough for habitability and for liquid water on their surfaces.

We can’t say more than that at the moment, but we can say there are a lot of rocks in our galaxy that look like the earth, and that could have water on their surfaces, and in fact we now know that probably most of the stars in the galaxy have Earth-like planets in a habitable zone.

DTH: Can we detect if there is life on these planets?

NL: …When that planet goes in front of the star it’s not just the rock that’s blocking the star, it’s also the atmosphere of the planet, so we can see the effects of that starlight being transported through the atmosphere of that planet. And that means that, say, the planet has oxygen in its atmosphere. The oxygen blocks particular colors of light.

And if, therefore, we look at the star as the planet goes in front of it and we see some of those colors of light disappearing that suggests that there’s oxygen in the atmosphere, and we don’t know how to make that much oxygen, at least in large quantities, apart from there being light on that planet.

DTH: If the star is a lot dimmer and a lot cooler than our sun, how likely is it that the planets around it have life on them?

NL: The key is that the star is much, much cooler than the sun, but the planets are much, much closer to the star. At the moment, what we can say is these planets are likely rocks with the same surface temperature as the earth. Beyond that there’s a whole host of questions.

Do they have enough water on their surfaces to have oceans? We have no idea. Is the star too active? Does it blast away the atmosphere of these planets over billions of years? We have no idea. Do the planets even have atmospheres that can support life like ours? We have no idea.

And then there are the questions of how life gets started. Is it easy to make life? Is it hard? We only have one example of a habitable planet.

We have no idea, but this is what we are working on trying to find out. And we are making leaps and bounds in figuring this out.

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