In the first-of-its-kind effort, scientists are getting ready to exploit the James Webb Space Telescope for the probing of atmospheres of rocky exoplanets orbiting red dwarf stars. The large-scale program will be about 500 hours in size, squarely aiming to answer one of the most tantalizing questions within astronomy: Can these distant worlds support atmospheres?
Smaller and cooler than our sun, red dwarf stars dominate the galaxy. Their planets often sport close orbits, offering a unique opportunity for study. The current atmosphere-detecting methods work best when planets are near to their stars; the cooler temperatures of red dwarfs allow those planets to be closer without getting scorched. Despite this potential, the presence and composition of atmospheres around these worlds remain a mystery.
This is the ambitious survey that will be led by JWST, a collaboration between NASA, the European Space Agency, and the Canadian Space Agency. According to Néstor Espinoza, an astronomer who headed the implementation of this program, it was a “high-risk, high-reward” mission. He said that if atmospheres come up around these planets, then it would mean that life could appear in such kinds of environments. Otherwise, not finding any would underline how special our planetary system is.
Most astronomers would concur that the detection of atmospheres holds the key to the search for habitable worlds. The atmosphere of Earth is sometimes referred to as its “security blanket,” and without it, life as we know it would never have evolved, nor would it be maintained today. It clings onto oxygen, filters most of the harmful ultraviolet radiation, provides warmth, and allows for liquid water to exist on its surface.
So far, researchers have detected signatures of atmospheres around thousands of the 5,700 known exoplanets, but most were gas-giant planets similar to Jupiter sporting hydrogen-rich atmospheres. Now, the search for a terrestrial planet with a protective atmosphere was thus still elusive—but new findings by Webb bring forward hopeful candidates like 55 Cancri e, GJ 486 b, and LHS 1140 b.
It was initiated by Jennifer Lotz, who manages operations for both Webb and the Hubble Space Telescope at the Space Telescope Science Institute, using the director’s discretionary time. Such surveys have already given rise to transformative science campaigns like the Hubble deep field images. It will also include roughly 250 orbits of ultraviolet observations with Hubble to study the activity of red dwarf stars.
He referred to them as the “perfect dream team” for this mission and emphasized that Webb and Hubble would play a complementing role. This time, it would be Webb making observations of the secondary eclipse to isolate planetary signals, while Hubble investigates whether such planets can retain atmospheres in the face of continuous radiation from their stars.
The 10-20 rocky worlds being targeted are mostly in the temperature range of 200-450 Kelvin. “This campaign is going to move our understanding of rocky exoplanets forward,” said Kevin Stevenson, an astrophysicist at the Johns Hopkins Applied Physics Laboratory. He added that two of the strongest candidates for having an atmosphere were GJ 486 b and LTT 1445 A b.
This could be one giant leap toward answering the question, ‘Are we alone?’,” said Stevenson. “If most planets orbiting M-dwarf stars don’t host atmospheres, then future instruments like the Habitable Worlds Observatory will become all the more essential to searching for extraterrestrial life.”.
“This atmospheric detection breakthrough might set JWST’s course and, indeed, all observatories hereafter, into the future,” says Sarah Moran, an exoplanet scientist at the University of Arizona. “Confirmation of an atmosphere on a rocky world orbiting an M dwarf star may set the stage for further discoveries with the next generation of space telescopes.”.
This is an ambitious survey, beginning where others have left off, with the scientific world waiting with bated breath for the results of this long quest to understand the possibilities of life beyond our solar system.