This illustration shows what the exoplanet WASP-39 b might look like, based on current understanding of the planet. WASP-39 b is a hot, bloated gas giant with a mass 0.28 times Jupiter (0.94 times Saturn) and a diameter 1.3 times larger. than Jupiter, orbiting only 0.0486 AU (4,500,000 miles) from its star. The star, WASP-39, is fractionally smaller and less massive than the Sun. Because it is so close to its star, WASP-39 b is very hot and likely tidally locked, with one side facing the star at all times. Data collected by the Webb Near-Infrared Spectrograph (NIRSpec) show unequivocal evidence of carbon dioxide in the atmosphere, while previous observations by NASA’s Hubble and Spitzer Space Telescopes, as well as other telescopes, indicate the presence of water vapor, sodium and potassium. The planet probably has clouds and some kind of climate, but it may not have atmospheric bands like those of Jupiter and Saturn. Credits: NASA, ESA, CSA, Joseph Olmsted (STScI)
NASA’s Webb ushers in a new era of exoplanet science with the first unequivocal detection of carbon dioxide in a planetary atmosphere outside our solar system.
After years of preparation and anticipation, exoplanet scientists are overjoyed. NASA’s James Webb Space Telescope has captured a stunningly detailed rainbow of near-infrared starlight filtered through the atmosphere of a hot gas giant exoplanet 700 light-years away. The transmission spectrum of the exoplanet WASP-39 b, based on a single set of measurements made with the Webb Near-Infrared Spectrograph and analyzed by dozens of researchers, represents a hat trick of firsts: the first observation Webb’s official scientist of an exoplanet; the first detailed spectrum of exoplanets covering this near-infrared color range; and the first indisputable evidence of carbon dioxide in the atmosphere of a planet orbiting a distant star. The results are indicative of Webb’s ability to detect key molecules such as carbon dioxide in a wide variety of exoplanets, including smaller, colder and rocky planets. This shows that it is capable of providing information about the composition, formation and evolution of planets across the galaxy.
Watch this episode of Space Sparks to learn more about how the James Webb Space Telescope has found definitive evidence of carbon dioxide in the atmosphere of a gas giant planet orbiting a Sun-like star 700 light-years away.
NASA’s Webb detects carbon dioxide in exoplanet atmosphere
NASA’s James Webb Space Telescope has captured the first definitive evidence of carbon dioxide in the atmosphere of an exoplanet, a planet outside the solar system. This observation of a gas giant planet orbiting a Sun-like star 700 light-years from Earth provides important information about the planet’s composition and formation. The finding, which has been accepted for publication in the journal Nature, provides evidence that Webb may be able to detect and measure carbon dioxide in the thinner atmospheres of smaller, rocky planets in the future.
The exoplanet, WASP-39 b, is a hot gas giant with a mass about a quarter that of Jupiter (about the same as Saturn) and a diameter 1.3 times that of Jupiter. Its extreme swelling is partly related to its high temperature (about 1,600 degrees Fahrenheit or 900 degrees Celsius). Unlike the cooler, more compact gas giants in our solar system, WASP-39 b orbits very close to its star. In fact, it is only about one-eighth the distance between the Sun and Mercury and completes one circuit in just over four Earth days. The discovery of the planet, reported in 2011, was based on ground-based detections of the subtle, periodic dimming of its host star’s light as the planet transits or passes in front of the star.
Previous observations by other telescopes, including NASA’s Hubble and Spitzer space telescopes, revealed that the planet’s atmosphere contained water vapor, sodium and potassium. Webb’s unmatched infrared sensitivity has now also confirmed the presence of carbon dioxide on this exoplanet.
A transmission spectrum of the hot gas giant exoplanet WASP-39 b captured by Webb’s Near Infrared Spectrograph (NIRSpec) on July 10, 2022, reveals the first clear evidence of carbon dioxide on an exoplanet of the solar system. This is also the first detailed exoplanet transmission spectrum ever captured covering wavelengths between 3 and 5.5 microns. A transmission spectrum is made by comparing the starlight filtered through a planet’s atmosphere as it moves in front of the star, with the unfiltered starlight detected when the planet is next to the star. star Each of the 95 data points (white circles) in this graph represents the amount of a specific wavelength of light that is blocked by the planet and absorbed by its atmosphere. Wavelengths that are preferentially absorbed by the atmosphere appear as peaks in the transmission spectrum. The peak centered around 4.3 microns represents light absorbed by carbon dioxide. The gray lines that extend above and below each data point are error bars that show the uncertainty of each measurement or the reasonable range of possible true values. For a single observation, the error in these measurements is extremely small. The blue line is the best-fit model that takes into account the data, the known properties of WASP-39 bi its star (eg, size, mass, temperature), and assumed characteristics of the atmosphere. Researchers can vary the parameters of the model, changing unknown characteristics such as the height of clouds in the atmosphere and the abundance of various gases, to better fit and better understand what the atmosphere is really like. The model shown here assumes that the planet is made mostly of hydrogen and helium, with small amounts of water and carbon dioxide, and a thin veil of clouds. The observation was made using the NIRSpec PRISM bright object time series mode, which involves using a prism to spread the light from a single bright object (such as the star WASP-39) and measure the brightness of each wavelength of wave at certain time intervals. Credits: NASA, ESA, CSA, Leah Hustak (STScI), Joseph Olmsted (STScI). )
Filtered starlight
Transiting planets like WASP-39 b, whose orbits we observe from the tip rather than from above, can provide scientists with ideal opportunities to probe planetary atmospheres. During a transit, some of the starlight is eclipsed by the planet completely (causing overall dimming) and some is transmitted through the planet’s atmosphere.
Because different gases absorb different combinations of colors, researchers can analyze small differences in the brightness of light transmitted across a spectrum of wavelengths to determine exactly what an atmosphere is made of. With its combination of a puffy atmosphere and frequent transits, WASP-39 b is an ideal target for transmission spectroscopy.
A series of light curves from Webb’s Near Infrared Spectrograph (NIRSpec) shows the change in brightness of three different wavelengths (colors) of light from the star system WASP-39 over time while the planet transited the star on July 10, 2022. A Transit occurs when an orbiting planet moves between the star and the telescope, blocking some of the star’s light. This observation was made using the NIRSpec PRISM bright object time series mode, which involves using a prism to distribute light from a single object. bright object (such as the star WASP-39) and measures the brightness of each wavelength at set time intervals. To capture this data, Webb looked at the WASP-39 star system for more than eight hours, starting about three hours before the transit. and ends about two hours after the transit is complete. The transit itself took about three hours. Each curve shown here includes a total of 500 individual brightness measurements, approximately one per minute. Although all colors are blocked to some degree by the planet, some colors are blocked more than others. This happens because each gas in the atmosphere absorbs different amounts of specific wavelengths. As a result, each color has a slightly different light curve. During WASP-39 b’s transit, light with a wavelength of 4.3 microns is not as bright as light at 3.0 or 4.7 microns because it is absorbed by carbon dioxide. Credits: NASA, ESA, CSA, Leah Hustak (STScI), Joseph Olmsted (STScI)
First clear detection of carbon dioxide
The research team used Webb’s Near Infrared Spectrograph (NIRSpec) for their observations of WASP-39 b. In the resulting spectrum of the exoplanet’s atmosphere, a small hill between 4.1 and 4.6 microns presents the first clear and detailed evidence of carbon dioxide ever detected on a planet outside the solar system.
“As soon as the data appeared on my screen, the carbon dioxide feature grabbed me,” said Zafar Rustamkulov, a graduate student at Johns Hopkins University and a member of the Early Release Science team. of the JWST Transiting Exoplanet Community, who conducted this research. “It was a special moment, crossing an important threshold in exoplanet science.”
No observatory has previously measured such subtle differences in brightness of so many individual colors in the 3-5.5 micron range in an exoplanet transmission spectrum. Access to this part of the spectrum is crucial for measuring the abundance of gases such as water and methane, as well as carbon dioxide. These are gases that are thought to exist on many different types of exoplanets.
“Detecting such a clear signal of carbon dioxide in WASP-39 b bodes well for detecting atmospheres on smaller, Earth-sized planets,” said Natalie Batalha of the University of California, Santa Cruz, who leads the team
Understanding the composition of a planet’s atmosphere is essential because it tells us something about the origin of the planet and how it evolved. “Carbon dioxide molecules are sensitive tracers of the planet’s formation history,” said Arizona State University’s Mike Line, another…