The WASP-96 b image from JWST

Today in my third installment of images from the Webb space telescope, I’ll discuss this image, which is entitled “Exoplanet WASP-96 b.” In fact, this is not a pretty picture and it’s not even an image at all. Instead, we’re looking at a complicated chart with lots of lines, dots, and numbers. I’ll explain this later, but first let’s make sure we’re on the same page when it comes to exoplanets. Hang with me!

Let’s start with planets. Everyone knows about the planets in our solar system. Besides Earth, my personal favorite is Saturn with its wonderful ring structures. For centuries, we’ve studied our planets and their motion from our perspective on Earth. Some of the most profound discoveries in all of history have involved observations of our planets. Think Galileo, Isaac Newton, and Albert Einstein. Most everyone has heard of these guys, but you may not realize that many of their scientific contributions were related to the planets orbiting our Sun.

As much as we learned about our planets from this trio, an important question for a long-time was “is our solar system the only one?” In other words, are there extrasolar planets (or “exoplanets”) in orbit around distant stars? Not that long ago, the possibility of detecting an exoplanet seemed like science fiction. Stars are too bright, and our telescopes were not powerful enough. But in the 1990s, all that changed when astronomers developed techniques to detect exoplanets in orbit around distant stars. Today, there are more than 5000 known exoplanets and WASP-96 b is one of them!

The detection of an exoplanet is simple to understand. Just imagine how starlight darkens ever so slightly as the exoplanet passes between us and the star. During this time, Webb uses spectroscopy to analyze the composition of the exoplanet’s atmosphere. In my grad school days, I used spectroscopy extensively to analyze the chemical structures of materials in the lab that I couldn’t even touch. My experiments were mundane compared to Webb, but you get my point. Spectroscopy is commonly employed in many areas of science.

Now imagine you are a spectroscopy expert standing on the Moon. As the Moon orbits the Earth, you notice the Earth occasionally passes between you and the Sun. When this happens, some of the sunlight that reaches you has passed through the atmosphere of the Earth. This faint wisp of light seems trivial, but you’re curious so you turn on your fancy spectroscopy machine and point it at the light that just skims the edge of the Earth. Voila! Your fancy spectroscopy machine detects the presence of water, carbon dioxide, and other constituents in the Earth’s atmosphere. You can’t believe it, but without even standing on the Earth, you just learned a lot about the Earth from that fancy machine of yours. It sounds like magic, but it’s not. It’s just good, old-fashioned science. This is exactly how the JWST uses spectroscopy to analyze the atmosphere of distant exoplanets.

Which finally brings us back to the chart with all the lines, dots, and numbers. This chart is telling us that exoplanet WASP-96 b has water in its atmosphere. It’s that simple. Our solar system is not the only one with planets containing atmospheric water. That’s profound, but what’s next? Maybe Webb will soon detect other atmospheric constituents like we have on Earth. I find the possibilities intriguing and I’m looking forward to more spectroscopy from Webb. I hope you are too!

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