The James Webb Space Telescope Has Discovered Its First Exoplanet
It has officially been over a year since the James Webb Space Telescope was launched in December 2021. In the time since then, NASA and this next generation telescope have been very busy trying to make use of the limited amount of time available with this technology. However, the agency recently revealed one of the most significant discoveries yet.
Yesterday confirmed its first exoplanet thanks to Webb. These first observational results found an Earth-size, rocky planet that could open the door to many future possibilities. At 99% of Earth’s diameter, it’s almost exactly the same size as our home world. Over time NASA has discovered thousands of different exoplanets within the universe.
What makes this specific discovery so special has to do with Webb’s next steps and the upcoming discoveries. One of the main uses of the James Webb Space Telescope is to study the atmospheres of exoplanets, to search for the building blocks of life elsewhere in the universe. Here I will go more in-depth into this first exoplanet discovery, the significance of the event, what Webb plans to do next, and more.
First Exoplanet
Yesterday NASA tweeted saying, “A whole new world! 41 light-years away is the small, rocky planet LHS 475 b. At 99% of Earth’s diameter, it’s almost exactly the same size as our home world. This marks the first time researchers have used Webb to confirm an exoplanet.” The continued by mentioning, “Planet LHS 475 b is a few hundred degrees warmer than Earth and very close to its star, completing an orbit in just 2 days. However, its red dwarf star is much cooler than our Sun, so scientists theorize it could still have an atmosphere.”
An exoplanet is defined as a planet that orbits a star outside the solar system. Not long ago, the team chose to observe this target with Webb after carefully reviewing targets of interest from NASA’s Transiting Exoplanet Survey Satellite (TESS), which hinted at the planet’s existence. Webb’s Near-Infrared Spectrograph (NIRSpec) captured the planet easily and clearly with only two transit observations.
Among all operating telescopes, only Webb is capable of characterizing the atmospheres of Earth-sized exoplanets. The team attempted to assess what is in the planet’s atmosphere by analyzing its transmission spectrum. Although the data shows that this is an Earth-sized terrestrial planet, they do not yet know if it has an atmosphere. The telescope is so sensitive that it can easily detect a range of molecules, but they can’t yet make any definitive conclusions about the planet’s atmosphere.
The exoplanet was discovered by observing the changes in light as it orbits its star. NASA provided an image with data points to better illustrate this process. Here, a light curve from NASA’s James Webb Space Telescope’s (NIRSpec) shows the change in brightness from the LHS 475 star system over time as the planet transited the star on August 31, 2022. This dip in brightness along with the timing gave the agency enough information to not only determine there is a planet but also some of its features.
For one, they’ve determined it can’t have a thick methane-dominated atmosphere, similar to that of Saturn’s moon Titan. The team also notes that while it’s possible the planet has no atmosphere, there are some atmospheric compositions that have not been ruled out, such as a pure carbon dioxide atmosphere. “Counterintuitively, a 100% carbon dioxide atmosphere is so much more compact that it becomes very challenging to detect,”. Even more precise measurements are required for the team to distinguish a pure carbon dioxide atmosphere from no atmosphere at all. The researchers are scheduled to obtain additional spectra with upcoming observations this summer.
Webb also revealed that the planet is a few hundred degrees warmer than Earth, so if clouds are detected, it may lead the researchers to conclude that the planet is more like Venus, which has a carbon dioxide atmosphere and is perpetually shrouded in thick clouds. A member of the team commented, “We’re at the forefront of studying small, rocky exoplanets. We have barely begun scratching the surface of what their atmospheres might be like.”
In addition, NASA provided a transition spectrum that gives even more hints about the planet. As this spectrum shows, Webb did not observe a detectable quantity of any element or molecule. The data (white dots) are consistent with a featureless spectrum representative of a planet that has no atmosphere (yellow line). The purple line represents a pure carbon dioxide atmosphere and is indistinguishable from a flat line at the current level of precision. The green line represents a pure methane atmosphere, which is not favored since if methane were present, it would be expected to block more starlight at 3.3 microns. All of which are factored in when trying to determine different features of this exoplanet.
Importance of Exoplanets
Now that we know more about Webb’s recent discovery and some of its upcoming plans, we can take a closer look at the science used and how it will apply to future discoveries. The first solar system found outside our own did not involve a main sequence star like our own, but a pulsar. Since then agencies like NASA have found thousands of exoplanets (and in every sort of star system imaginable), and they continue to narrow in on smaller and more earth-like planets.
As partially mentioned prior, one method Webb will use for studying exoplanets is the transit method, which means it will look for dimming of the light from a star as its planet passes between us and the star. (Astronomers call this a “transit”.) Collaboration with ground-based telescopes can help measure the mass of the planets, via the radial velocity technique (i.e., measuring the stellar wobble produced by the gravitational tug of a planet), and then Webb will do spectroscopy of the planet’s atmosphere.
Webb also carries coronagraphs to enable direct imaging of exoplanets near bright stars. The image of an exoplanet would just be a spot, not a grand panorama, but by studying that spot, we can learn a great deal about it. That includes its color, differences between winter and summer, vegetation, rotation, and weather. Spectroscopy is simply the science of measuring the intensity of light at different wavelengths. The graphical representations of these measurements are called spectra, and they are the key to unlocking the composition of exoplanet atmospheres.
When a planet passes in front of a star, the starlight passes through the planet’s atmosphere. If, for example, the planet has sodium in its atmosphere, the spectrum of the star, added to that of the planet, will have what we call an “absorption line” in the place in the spectra where would expect to see sodium. This is because different elements and molecules absorb light at characteristic energies; and this is how we know where in a spectrum we might expect to see the signature of sodium (or methane or water) if it is present. Why is an infrared telescope key to characterizing the atmospheres of these exoplanets? The benefit of making infrared observations is that it is at infrared wavelengths that molecules in the atmospheres of exoplanets have the largest number of spectral features. The ultimate goal, of course, is to find a planet with a similar atmosphere to that of Earth.
In addition to studying planets outside our solar system, scientists want to learn more about our own home. Webb actually complements NASA’s other solar system missions, including those observatories on the ground, orbiting Earth, and in deep space. Data of different wavelengths and from different sources can help build a broader, fuller picture of the objects in our solar system, especially with the help of Webb’s unprecedented improvements in sensitivity and resolution. Webb will observe Mars and the giant planets, minor planets like Pluto and Eris – and even the small bodies in our solar system: asteroids, comets, and Kuiper Belt Objects. For example, Webb will help us to understand the trace organics in Mars’ atmosphere, and be used to do studies that verify the findings of the Mars rovers and landers. In the outer solar system, Webb’s observations of the outer solar system will be used with Cassini’s Saturn observations to provide a better picture of the seasonal weather on our giant gas planets.
Lastly, focusing back on the telescope and its current progress, Webb is trying to make up time. Specifically, the James Webb Space Telescope resumed science operations Dec. 20, after Webb’s instruments intermittently went into safe mode beginning Dec. 7 due to a software fault triggered in the attitude control system, which controls the pointing of the observatory. During a safe mode, the observatory’s nonessential systems are automatically turned off, placing it in a protected state until the problem can be fixed. This event resulted in several pauses to science operations totaling a few days over that time period. Science proceeded otherwise during that time. The Webb team adjusted the commanding system, and science has now fully resumed. NASA points out that the observatory and instruments are all in good health, and were not in any danger while Webb’s onboard fault management system worked as expected to keep the hardware safe. The team is working to reschedule the affected observations.
Conclusion
NASA just announced that the JWST has officially discovered its first exoplanet. This is a significant first step and is expected to reveal much more information in the coming years. We will have to wait and see how it progresses and the impact it has on the space industry.
