By Jonny Lupsha, Wondrium Staff Writer
Today, the James Webb Space Telescope launched from French Guiana. The once-in-a-generation mission will send an infrared telescope a million miles away to study the Universe. What does it mean for exoplanet research?
First conceived in 1996, the 25-year dream that became the James Webb Space Telescope (JWST) has become a reality. The $10 billion telescope will look further back in time than its predecessor, the Hubble Space Telescope, using infrared technology. One benefit of the JWST’s infrared tech, as covered in the first article in The Great Courses Daily‘s three-part series on the telescope launch, is that it can observe the earliest galaxies and stars in the Universe.
Another benefit is that it can study atmospheric conditions of exoplanets throughout the galaxy. In this second article about the JWST, our exclusive interview with Dr. Sarah Rugheimer, Glasstone Research Fellow at Oxford University and host of the Audible Audiobook Searching for Extraterrestrial Life, continues. Dr. Rugheimer explains the importance of exoplanet research, including the atmospheric makeup and habitability of planets in other star systems.
Exoplanet Research: From Theory…
In order to understand the importance of the JWST’s exoplanet research, it helps to first look at Dr. Rugheimer’s field of astrobiology and her work in it.
Planets orbiting other stars sometimes share certain characteristics with Earth, which means we can apply known physics and chemistry concepts that we’ve confirmed on Earth to other planets as we study them. However, Earth didn’t always look how it does today.
“It’s gone from this lava sort of Hellish state to a planet covered in oceans with small islands dotting the surface with only microbial life, and then eventually to a planet with land plants and global glaciations,” Dr. Rugheimer said. “Earth’s been so many planets through its four-and-a-half-billion-year history. That’s the focus of my research, how Earth has looked through time and how it might change under a different type of star.”
The many sizes and classes of stars give off different kinds of radiation, and the resulting light then interacts with the atmospheres of planets orbiting those stars. Dr. Rugheimer added that when the light and the atmosphere combine, they create different chemical abundances in the atmospheres of the exoplanets. Since Dr. Rugheimer is a theorist, she codes known physics into computer models to discover more about exoplanet atmospheres. She models the star’s radiation and its interaction with the atmospheres to provide answers for what exoplanets should look like when seen through telescopes like the JWST.
“That’s where the link is with observations,” Dr. Rugheimer said. “I do theoretical models and observers take those models and say, ‘Oh, could we see that feature with this instrument [like the JWST]?’ or ‘What’s the amount of time we need to observe it?’ or ‘What wavelengths should we prioritize?'”
With the help of astrobiologists like Dr. Rugheimer, scientists looking through the JWST will have a better picture of what to look for when studying exoplanets. Previous missions have offered minute glimpses into exoplanet atmospheres, but the JWST will be the first major telescope designed to do so. Focusing mainly on planets the size of Neptune and Jupiter, but also including some Earth-sized planets, the JWST will use its infrared tech to further the study of these other planets.
The JWST will also advance astrobiology.
“We’re only going to be able to look at a few planets, but it’s this first step,” Dr. Rugheimer said. “We have to walk before we can run. We will cut our teeth on characterizing some of these larger planets. We’ll do a really good job learning a whole bunch of things about planets that are a bit bigger than Earth. Planets that are Jupiter- or Neptune-sized, and some rocky planets that are a bit bigger than Earth, called super-Earths.
“We’re going to find [out] a whole lot more about this diversity of exoplanets.”
The Transit Technique
Due to their different wavelengths, the visible range and infrared range of the electromagnetic wave spectrum show different things. For example, Dr. Rugheimer said that the visible range is the best place to look for oxygen as O2 in an atmosphere. Other molecules like methane and ozone show in the infrared. In fact, more molecules have features in the infrared range and leave “spectral fingerprints” that are detectable with the JWST.
What is a spectral fingerprint?
“Light interacts with molecules in a very specific way,” Dr. Rugheimer said. “James Webb will be using the transit technique—a planet will cross in front of the star and the light will go through the atmosphere. We can take observations of the planet when it’s in front of the star and when it’s not and you can see how that light has changed by the presence of the atmosphere.
“[Some of] the light going through the top layers of an atmosphere will be absorbed; it won’t get to us in the wavelengths where those molecules are.”
Instruments on the James Webb Space Telescope such as spectrographs collect the light and break it apart into different colors, telling astronomers what passed through at one wavelength or another. Doing that provides a spectrum, or fingerprint, of what’s in the atmosphere.
“It’s the very first telescope where we might find signs of life on another planet,” she said.
In our final article covering the James Webb Space Telescope launch, Dr. Rugheimer will explain how exoplanets’ spectral fingerprints can indicate alien life and where the telescope is most likely to find it.