Will astronomers ever be able to confirm life exists on other planets? – Technology & Science

Scientists continue to seek signs of life outside our solar system, but how will they know when they find it?

Astronomers announced Wednesday they had found seven Earth-sized planets orbiting a star 39 light-years away. Three of the planets lie within the “habitable zone,” a theoretical range in which liquid water could exist. 

The scientists plan to study the atmospheres using telescopes including the Hubble Space Telescope in an effort to determine if there is actually life flourishing on these far-off worlds.

To understand what’s involved in searching for signs of life, you need to first know two definitions astronomers use: potentially habitable and habitable.

Potentially habitable means that a planet lies within an theoretical zone around a star where liquid water can exist on its surface. Habitable, exoplanet researcher Sara Seager told CBC News, means there’s water vapour.

This diagram shows how the habitable zones of larger stars are wider and farther away the hotter the star is. (NASA/Kepler Mission/Dana Berry.)

Each time astronomers discover Earth-like planets, the immediate question is: Is there life on it? But that question may be harder to answer than it first appears.

“We don’t know how life emerges,” Amaury Triaud, co-author of the study on the new discovery, said at a news conference Wednesday.

If life emerges from an ocean of water, then it will be easier for us to find, he said. But if life forms through other means, or can thrive in an atmosphere laden with gases in which we can’t live, then we could miss it.

‘There are plenty of science fiction books that say if you have oxygen you have life. But that’s not true.’
Michaël Gillon

We only know of carbon-based life, life that requires water to survive. As a result, we look for gases emitted into the atmosphere that are detectable. And that’s how astronomers are looking for signs of life.

“We’re very Earth-centric,” said Seager, a Toronto-born professor…

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