James Webb Space Telescope will search TRAPPIST-1 planets for signs of life
The seven Earth-sized planets discovered last month orbiting the star TRAPPIST-1 will be ideal targets for the James Webb Space Telescope (JWST), scheduled for launch next year, to probe in a search for signs of life.
Viewed as the Hubble Space Telescope’s scientific successor, JWST, a joint project of NASA, the European Space Agency (ESA), and the Canadian Space Agency, will observe in the infrared and use spectroscopy to identify the chemical contents of exoplanets’ atmospheres.
Spectroscopy separates light into individual wavelengths. Every chemical has its own unique wavelength signature, so the technique is capable of identifying individual atmospheric components.
This means JWST will be able to search the atmospheres of all seven TRAPPIST-1 planets – assuming all have atmospheres – for chemicals produced by biological processes, known as chemical biomarkers.
Two such chemicals are ozone and methane. On Earth, ozone forms mostly through interaction between oxygen produced by plant life during photosynthesis and sunlight. Atmospheric ozone also protects life on Earth from harmful solar radiation.
Finding methane could be a first step toward locating a biological source of the oxygen that goes into the formation of ozone.
“If these planets have atmospheres, the James Webb Space Telescope will be the key to unlocking their secrets. In the meantime, NASA’s missions like Spitzer, Hubble, and Kepler are following up on these planets,” said NASA Exoplanet Program scientist Doug Hudgins.
Being Earth-sized is not the only factor that makes the TRAPPIST-1 planets perfect targets for JWST. At 40 light-years away, the system is relatively nearby. Three of them orbit in their star’s habitable zone, where temperatures allow liquid water to exist on their surfaces.
With the red dwarf TRAPPIST-1 star being so small and dim, signals from the planets will be large enough and strong enough for scientists to isolate their individual atmospheric components.
A planet’s ability to support life depends not just on its atmosphere containing chemicals such as oxygen, ozone, methane, carbon monoxide, carbon dioxide, and water, but also on the proportions of these chemicals within the atmosphere.
JWST’s infrared capability will identify the contents of the TRAPPIST-1 planets’ atmospheres while its spectroscopy will determine the proportions of these biosignatures.
Observations will especially focus on the three planets in the star’s habitable zone, TRAPPIST-1 e, f, and g. With the right atmospheric composition, one or more could have an environment capable of supporting liquid water.
Because the seven planets are so close to one another, scientists will be able to study all of them with JWST and compare them with one another in terms of composition and processes.
“This is the first and only system to have seven Earth-sized planets, where three are in the habitable zone of the star,” noted Hannah Wakeford, a postdoctoral fellow at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
“It is also the first system bright enough, and small enough to make it possible for us to look at each of these planets’ atmospheres. […] With all seven planets Earth-sized, we can look at the different characteristics that make each of them unique and determine critical connections between a planet’s conditions and origins,” she added.
The most powerful space telescope ever built, JWST is scheduled to launch in October 2018, so the discovery of the TRAPPIST-1 system is ideal timing, and scientists are eager to aim the telescope at these seven worlds.
Currently, JWST, which has a 6.5-meter (∼21 feet) primary mirror, is at Goddard undergoing testing by engineers and scientists.
In addition to teasing out the atmospheres of exoplanets, the telescope will also observe the universe’s earliest galaxies and use its infrared capability to look into dusty clouds to view the formation of stars and planetary systems.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.