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New prospects of life on other planets

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April 26th, 2017
Artist's concept of what the surface of the planet called TRAPPIST-1f might look like.
Artist's concept of what the surface of the planet called TRAPPIST-1f might look like.

It has been a while since NASA has put a human being into space, but the federal agency still has its eyes on the stars. Since the 2015 discovery of a faraway star system using the TRAPPIST (Transiting Planets and Planetesimals Small Telescope) ground telescope in Chile, the term extraterrestrial life has come up quite a bit.

Astronomers happened to notice that the TRAPPIST-1 system, as it’s called, contains seven orbiting planets, known as “exoplanets” because of their proximity to Earth. And at least three of these planets are potentially habitable by living creatures. 

Recently, the Tribune spoke with NASA Headquarters Program Scientist Kartik Sheth about the discovery and what it means to our long-running search for life in outer space. 

Tribune: What exactly is an “exoplanet”?

Sheth: An “exoplanet” is a planet that is revolving around a star that is not our star. There are about 400 billion stars in our Milky Way, and our data suggest that nearly every one of these has a planet around it.

Tribune: When did this discovery take place?

Sheth: The first indication that this star had planets around it occurred in 2015. We named this system TRAPPIST-1 after the ground telescope that was used to discover it. 

During observations, astronomers could see [black] gaps in the starlight. This indicated a cycle of eclipses caused by planetary bodies orbiting the star.

At first, they thought there were three planets in orbit. But using a series of additional ground telescopes around the world, they were able to consistently observe the star for about 20 days, which revealed a more complex planetary system.

Tribune: Why was this process necessary?

Sheth: As the planets orbit, they move across the disk of the star, causing an eclipse. These eclipses happen over periods ranging anywhere from a few days to as many as 20 days.

Ultimately, we observed 34 eclipses, which corresponded to seven planets orbiting this star. 

Tribune: How far away are these planets?

Sheth: This star system is 40 light years away. In other words, traveling at the speed of light [roughly 670 million mph], it would take us 40 years to get there. 

And that’s actually around the corner by an astronomer’s standards.

Most of the exoplanets discovered with the Kepler space telescope are about ten times farther away. To put this in perspective, the center of our Milky Way is 25,000 light years from Earth, so, relatively speaking, TRAPPIST-1 is nearby.

That’s why we’re so excited about this. It’s so close that our telescopes have the potential to really see the system in detail, again, relatively speaking. It would be harder if the star was farther away.

Tribune: NASA reports that there may be at least the potential for some form of life on a few of these planets. What prompts you to believe that?

Sheth: Let me first unequivocally say that we do not know if there is life on any of these planets. What we do know, however, is that three of these planets are in what we call “the habitable zone.” 

That means they’re just the right distance from their parent star that if there were any water on them, it would be liquid in nature.

That is, they would be getting the same amount of heat from their star that Earth does from the Sun. We think planets e, f, and g are the most likely to have liquid water. 

Since we know that life on our planet was formed in water, these are the planets where we want to look for biosignatures. 

Tribune: What kind of biosignatures?

Sheth: For example, if we see a water-rich atmosphere, that could be a sign of oceans. Other biosignatures that astronomers can predict are methane and ozone in certain proportions. 

We’ll be looking for those elements that are necessary to the existence of life. So understanding what the atmospheric constituents are is the next step, and from that, we can determine whether our findings indicate the strong possibility of life on the planet.

Tribune: What does this hold for the future?

Sheth: The future is very exciting in this case. We don’t have just one planet in this habitable zone, but three. 

Everything starts as educated and perhaps even imaginative speculation. At one time, we could only speculate on the surface of the moon or the surface of Mars. 

We once thought Earth was flat and at the center of the universe, that the Sun and all of the other planets revolved around Earth.

The discovery of new planets, such as those around TRAPPIST-1, reinforce the sheer breadth of space and, thus, the possibility that there’s life out there at some level.


Does the discovery of this star system mean that extraterrestrial life may exist elsewhere in space? Share your thoughts in the comments section below.

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