Aug 16, 2022 - Science

A new chapter in the search for alien planets

Animated illustration of a planet with a blinking neon vacancy sign

Illustration: Natalie Peeples/Axios

Scientists are entering a new era of space science — one that will be defined by not simply searching for planets circling distant stars, but by figuring out whether any of them could support life.

Why it matters: For the past 30 years, researchers have focused on finding these worlds, collectively called exoplanets, discovering more than 5,000 of them since the first ones were detected in 1992.

  • Now — thanks to sensitive telescopes on Earth and in space — astronomers have a chance to learn more about how planets form and their odds of habitability.

What's happening: A study published in The Astrophysical Journal Letters used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to find what scientists think is one of the youngest planets ever discovered, at only 1.5 million years old.

  • The world — which is about the mass of Jupiter — isn't habitable, but the researchers revealed a possible cloud of dust and gas, called a circumplanetary disk, around the planet that could one day form moons or rings.
  • "Even within the solar system, we don't understand how satellites have formed," Jaehan Bae, an author of the study, tells Axios, explaining that it's still not clear how Earth's Moon or Jupiter's large Galilean moons formed, but that this kind of study could help scientists learn more.
  • The James Webb Space Telescope recently observed the star system and should be able to confirm the presence of the world if it's there, Bae says.

The big picture: Understanding the chemical compositions of newly formed planets, their stars, and disks of gas and dust around young stars will help researchers learn more about the likelihood of habitability in various star systems.

  • Scientists have collected "stellar abundance profiles" of stars for a number of years, allowing them to break down exactly what chemicals, in what ratios, make up various stars. Now, thanks to large-scale surveys, researchers have been able to collect tens of thousands of these profiles.
  • By pairing those stellar chemical thumbprints with the chemistry happening inside of disks of forming planets, researchers might be able to figure out what elements are being incorporated into planets and how it could affect their habitability.
  • "The ratios of things like magnesium silicate to phosphorus to carbon to oxygen might all be super important," exoplanet scientist Jessie Christiansen says of habitability.
  • "Suddenly, we're at this moment where you are going to have exoplanet atmosphere detections and you want to know the physical processes that created that planet to be able to start considering anything like bio-signatures," exoplanet scientist Meredith MacGregor tells Axios.

Yes, but: Understanding habitability in general is about more than chemical composition, mass and position in orbit.

  • The way life evolved on Earth is complex, and it's only one data point, making it difficult to know what was important to our planet versus what can be generalized as a necessity for life to exist.
  • For example, scientists think that the first life on Earth may have developed in tide pools governed by the movements of the Moon around our planet, so it's possible a Moon might be essential to developing life, Christiansen says.
  • Scientists also think that the large planets in the outer solar system were responsible for sending comets toward Earth, delivering water and allowing life to thrive. The question now is: How important are those gas giants to creating the right environment for life?

What to watch: The JWST is a powerful new tool when it comes to understanding exoplanets and the disks of debris and gas that form them around distant stars.

  • The telescope is designed to parse out the chemical composition of the atmospheres enveloping exoplanets, allowing scientists to learn more about their formation and evolution.
  • But the future of exoplanet science is not just about JWST. "I'm really excited about leveraging [different telescopes] to learn more — not just using JWST, but using JWST and ALMA and trying to use as many telescopes as we can to get these really unique datasets that give us as much information as possible," MacGregor says.
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