A gas giant planet orbiting a Sun-like star 700 light years away has been observed by the James Webb Space Telescope (JWST), a collaboration between NASA, the European Space Agency, and the Canadian Space Agency, and it has been shown to have carbon dioxide in its atmosphere.
The finding, which has been accepted for publication in
Nature, offers crucial insights into the composition and genesis of exoplanets
and shows that Webb is capable of detecting and measuring carbon dioxide in the
thinner atmospheres of tiny rocky planets. Furthermore, a deeper comprehension
of these exoplanets may help in the search for planets that may be home to
extraterrestrial life.
Through the Early Science Publication Programme, which was
chosen to gather some of Webb's initial data once its science operations
started in late June, the team that made the finding was given access to the
telescope. The team is led by astronomers from the University of California,
Santa Cruz, including Björn Benneke of the Université de Montréal, who is also
a member of the Institute for Exoplanet Research (iREx), as well as astronomers
from other countries.
WASP-39 b, the object of the monitoring programme, is a hot
gas giant with a mass nearly equal to that of Saturn and a diameter that is 1.3
times that of Jupiter. Due in part to the high temperature (about 900°C), it is
unusually puffy.
WASP-39 b orbits its star very closely, only approximately
one-eighth the distance between the Sun and Mercury, and completes one orbit in
just over four Earth days, in contrast to the colder, more compact gas giants
in our Solar System.
The planet's discovery, announced in 2011, was based on ground-based observations of the star's host star's light decreasing subtly and repeatedly when the planet transits, or passes in front of, the star.
During transit, part of the sunlight passes through the
planet's atmosphere and some is entirely blocked by the planet (resulting in
total darkening). Researchers can analyse subtle variations in the brightness
of transmitted light across a spectrum of wavelengths to precisely identify the
composition of the atmosphere because different gases absorb different
combinations of colours.
WASP-39 b is a good target for transmission spectroscopy
because of its inflated atmosphere and regular transits. The scientists made
this discovery using Webb's (NIRSpec).
The first conclusive evidence of carbon dioxide on a planet
beyond the Solar System is revealed in the transmission spectrum of the hot-gas
exoplanet WASP-39 b, observed by Webb's (NIRSpec) on July 10, 2022.
The discovery crew witnessed something very amazing. At infrared wavelengths between 4.1 and 4.6 microns, a substantial signal—an absorption feature—was found. This is the first time that carbon dioxide has ever been identified in such abundant detail on a planet outside of the solar system.
"I was absolutely blown away," said Benecke, a
professor of physics at the University of the Netherlands and a member of the
Transiting Exoplanet Team. Benecke collaborated with graduate students
Louis-Philippe Coulomb, Caroline Piolet, Michael Radica, and Pierre-Alexis Roy
as well as postdoctoral fellow Jake Taylor on the design of the observing
programme and the analysis of the NIRSpec data.
"While examining the data here in Montreal, we
discovered a massive carbon dioxide signal that was 26 times stronger than any
background noise. We frequently investigated the noise prior to JWST, but this
time we had a totally reliable signature. It resembles having your own eyes
open and seeing something clearly.
Professor Björn Benneke, of the Université de Montréal and
iREx, was an important contributor to the team that identified the first unmistakable
trace of carbon dioxide in an exoplanet's atmosphere.
In the exoplanet transmission spectrum, no observatory has previously observed such minute variations in the brightness of so many distinct infrared colours.
The ability to measure copious gases thought to exist in a
variety of exoplanet types, including as water, methane, and carbon dioxide,
requires access to this region of the spectrum, which spans from 3 to 5.5
microns.
"Finding such a clear carbon dioxide signal on WASP-39
b bodes well for the discovery of atmospheres on smaller Earth-sized
planets," said Batala, the program's lead scientist.
"On Earth," continued Beneke, "carbon dioxide
plays such a significant role in our climate, and we are accustomed to
detecting its spectroscopic traces here. We can now see that signature on a
faraway planet. The point that these exoplanets are genuine worlds, just like
Earth and the planets in our solar system, is particularly driven home by this.
The most important observatory for space science in the
world is the James Webb Space Telescope. Webb will study the fascinating
architecture and origins of our cosmos and our place in it. He will also look
beyond the solar system to faraway planets around other stars. A global
initiative run by NASA, ESA (the European Space Agency), and the Canadian Space
Agency is called Webb.
Reference: NASA