JWST heralds a new dawn for exoplanet science
A future historian of space science in the 21st century would divide the subject into two eras: before the James Webb Space Telescope (JWST) and after. The telescope was built to transform our understanding of the universe by studying the first stars and galaxies, and within less than a year of operations, it was already done. The results are baffling and perhaps revolutionary From his observations of the early universe. However, JWST’s work is poised to transform many other subfields of astronomy, arguably none more than the study of exoplanets, the worlds orbiting other stars. Astronomers know now from More than 5,000 planets outside the solar system, but they don’t know anything Around Most of them – their composition, environmental conditions or even life prospects. JWST is setting out to change that, thanks to its hitherto unmatched ability to directly observe these alien worlds, slicing through the light to distinguish fine details and even occasionally able to snap an image of an exoplanet against the overwhelming glow of its parent star.
These results remain a far cry from the astrobiological chalice of finding and studying Earth-like worlds, but they are very exciting nonetheless, given that the JWST and its primary science goals were conceived before exoplanets appeared. “The exoplanet community is just spinning right now,” says Mark Clampin, director of the Astrophysics Division at NASA Headquarters in Washington, D.C.
JWST’s first science year is scheduled to run from July 2022 through June 2023. From that period, called the first cycle, a quarter of the telescope’s time is devoted to exoplanets across some 75 programs. One of the most exciting applications of JWST is the study of exoplanet atmospheres. Plated in gold and as wide as a full-grown African elephant, the telescope’s infrared-tuned primary mirror allows probes of exoplanet atmospheres to a degree never before possible. with Hubble [Space Telescope]”We’ve spent a decade discovering water, which we’ve discovered in abundance, but not much more than that,” says Nicole Lewis of Cornell University. “It was the only thing you could measure.” JWST can see water, too — as well as a much wider range of molecules including carbon dioxide, sodium, and more. Some of the compounds JWST can detect, such as methane, are closely associated with metabolic processes in Earth’s biosphere, making them biosignatures that could help reveal the presence of life on other potentially habitable worlds beyond the solar system.
In August, astronomers revealed they had used the JWST chart Carbon dioxide detection on an exoplanet for the first time by observing signs of gas in the light of a gas giant planet’s host star filtering through the world’s atmosphere. This technique is known as transmission spectroscopy, and it’s incredibly useful not only for studying giant planets but also for examining smaller planets that may be more like the footnote of our solar system than rocky worlds. “We needed to start with, ‘Well, do they have air?'” says Lewis. “Once we understand this, we can develop a better strategy for searching for biosignature gases.”
At the 241st meeting of the American Astronomical Society (AAS) in Seattle earlier this month, astronomers announced another transmission spectral analysis result from JWST. This time the telescope studied an Earth-sized world called LHS 475 b, which orbits a red dwarf star 41 light-years from Earth. In this case, JWST in fact Confirm the existence of the planet, which was previously hinted at by NASA’s Transiting Exoplanet Survey Satellite (TESS). “We confirmed it’s a planet by observing it with JWST,” says Sarah Moran of the University of Arizona, a collaborator on the finding.
JWST observed the planet’s two orbits around its star, but additional observations expected in May will be needed to better analyze the contents of the planet’s atmosphere. Even now, “the team can say a lot of things about what the atmosphere doesn’t look like,” says Moran. We know that hydrogen does not dominate like Jupiter or Saturn. We think it probably doesn’t have an Earth-like atmosphere. But it can have a carbon dioxide atmosphere like Venus or Mars, or it can have no atmosphere at all like Mercury.” The findings could help study other rocky planets around red dwarfs, which account for about three-quarters of All the stars are in the Milky Way.”We are in the early stages of trying to measure the atmospheres of rocky planets and trying to see if the planet could be habitable,” Moran says.
In terms of studying rocky planets, the James Webb Space Telescope is largely limited to worlds orbiting red dwarfs, which are dim enough to avoid overloading the telescope’s highly sensitive optics. Such stars are known to be prone to intense flaring that can blow out the atmospheres of worlds like LHS 475 b, which orbit perilously close to their host stars than the wider interstellar-planetary divides between rocky worlds in our solar system. “There is a possibility that all of their atmospheres were blown away by their stars,” says Lewis. One of the major red dwarf targets of interest, the TRAPPIST-1 system about 40 light-years from Earth, contains seven Earth-sized worlds. Many of these are located in a star’s habitable zone – the region around the star in which the planet’s warm starlight might allow liquid water to exist. Early observations of TRAPPIST-1 are still in progress, including those looking at the atmosphere. These findings could go a long way toward revealing whether red dwarf worlds could actually be habitable. “Hopefully, we’ll know by the end of the first cycle,” Lewis says.
The JWST also has an interesting add-on called a honagraph, a device for blocking most starlight so that fainter companion planets can be seen (this was crucial to JWST’s first exoplanet image, which the researchers made It was unveiled last September). The power of suppressing starlight from the telescope’s telescope is insufficient to detect any small potentially habitable worlds, but recent work has shown that the coronagraph should allow JWST to see worlds down to the size of Jupiter or Saturn orbiting red dwarf stars in or around after him. Five times the distance between Earth and the Sun (five astronomical units, or AU). This is roughly the location of Jupiter in our solar system.
This analysis comes from Glen Lawson of NASA’s Goddard Space Flight Center and colleagues, who first appeared at a recent AAS meeting. Stunning infrared views of a sprawling debris disk It surrounds a young star 32 light-years from Earth. “In the past, direct imaging was limited to 10 or so Jupiter masses,” says Lawson. Here we are sensitive to [single] The mass of Jupiter.” This will allow JWST to search for approximate analogues of Jupiter around other stars in a way that has not been possible before. “Our hope is that, with JWST, we can constrain the presence of planets in this system,” says Lawson. Such planets can be identified The imager is directly in orbit around its stars, providing an excellent opportunity to “go on and get a lot of really amazing data.”
Astronomers are also excited about the exoplanet potential of another telescope, the European Space Agency’s (ESA) Gaia observatory. Launched into space in 2013 primarily to map the motions and locations of billions of stars in our galaxy, the telescope is also expected to find thousands of exoplanets. At the AAS meeting, Sasha Hinckley of the University of Exeter in England — who leads one of the first exoplanet imaging programs at JWST — announced that using Gaia and the Very Large Telescope (VLT) in Chile, his team had seen an unusual planet about 130 light-years from Earth. It appears to be undergoing nuclear fusion. “It burns deuterium,” he says, referring to the isotope of hydrogen that achieves nuclear fusion that powers starlight at temperatures lower than regular hydrogen. Hinckley says further studies of the system could help astronomers draw less blurry lines between stars, planets and brown dwarfs — the latter a loosely defined class of objects that lie between planets and stars in mass. The planet 130 light-years away, spotted thanks to Gaia seeing its host star’s motion wobble due to the gravitational pull of the unseen world, could be one of several upcoming exoplanets discovered by the telescope, some of which could also be interesting targets for JWST.
However, it appears that the search for Earth-like worlds will determine the legacy of JWST’s exoplanet despite being beyond the reach of a telescope. “That’s where all of this work is headed, and that’s why the majority of people are involved in this game,” says Hinckley. In 2026, a new ESA mission called PLATO will be launched, with finding such worlds as its primary goal. PLATO will stare out at vast expanses of the sky, for the first time, to seriously search for Earth-like worlds around sun-like stars within 1,000 light-years of the solar system. A few dozen such planets are expected to be found during the telescope’s initial four-year mission, says Ana Heras of the European Space Agency, the mission’s project scientist. “We really don’t know what the incidence is [for Earth-like planets]she says. PLATO will go so far as to tell us how many, if any, are in the corner of the galaxy.
JWST will not be able to study such worlds closely. Nor will its successor, the Nancy Grace Romanian Space Telescope, due for launch by 2027, be able to do so. But Roman will play a crucial role alongside his other science goals: testing advanced coronagraph technology that will be needed to produce images of potentially habitable Earth-like worlds around stars like our sun. This technology is then supposed to be used in JWST and Roman’s successor, It was newly named the Habitable Worlds Observatory, which is scheduled to launch no later than the late 2030s with a mission to produce the first-ever images of a potentially habitable Earth. Such a telescope would have to be “about 100 times more stable” in space than the James Webb Space Telescope to achieve such a goal, says Bruce McIntosh, director of the University of California Observatories. “This is no small challenge.”
The road to this possibility is long. “We’re at the very beginning of the journey here,” Clampin says. But even setting aside any talk of holy grails, the early transformational results of exoplanets in the JWST remain exciting for scientists. However, the best is yet to come. “People need to be patient,” says Lewis. “The first course is all about picking the low-hanging fruit. We’re going to go crazy for the next few courses.”