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On Friday, NASA continued to build the hype for next week's image release from the Webb Space Telescope by announcing the five objects in the first cache of images. A few of the targets are exactly what you'd expect, given what scientists have said they want to use the telescope to image, while a couple have likely been chosen because they'll produce some fantastic visuals.
The target list also shows NASA's thoughts about how it can get informative data as quickly as possible. We'll give a little background on each of the targets below.
WASP-96 b: One of the most exciting features of Webb is its ability to analyze the composition of the atmospheres of exoplanets. When a planet passes between its host star and Earth, some of the star's light will pass through its atmosphere, allowing the materials in the atmosphere to absorb specific wavelengths in the star's light. This signal is tiny since only a small fraction of the star's light will pass through the atmosphere, so it will typically take months of observations to get a good signal.
WASP-96 b allows us to get a good signal much more quickly, as it's a planet composed mostly of atmosphere. While it's about half the mass of Jupiter, it is physically larger, indicating that it's mostly made of gas. It also has an orbital period of just 3.4 days, which means we can image its atmosphere twice a week. NASA will show the infrared spectrum of light that has made it through the atmosphere and will undoubtedly highlight the spectral signatures of molecules in the planet's atmosphere.
The Carina Nebula: This will probably be a "just showing off" image. The Carina Nebula is a huge cloud of gas lit by the massive stars that are forming within it. It's home to the most luminous star we've identified in the Milky Way, as well as Eta Carinae, my favorite candidate for "most likely to go supernova." The star came so close to destroying itself in a massive eruption about 175 years ago that it formed a nebula within the Carina Nebula.
This image will look spectacular. And there's potentially interesting science to be done here. Webb should have the resolution to work out smaller-scale structures within the nebula and maybe even determine the flow of gas in some regions based on the changes in the spectrum caused by red- and blue-shifting. Finally, Webb may be able to detect some interesting molecules in the cooler areas of the nebula. But I suspect it will take some time to come down from the awe-inspiring aspects of the image before anyone pays attention to the science.
SMACS 0723: The wavelengths to which Webb is sensitive were chosen for a very specific reason: By the time the light from the Universe's first stars finishes traveling most of the way across the Universe, it will have been red-shifted right into the area of the spectrum to which Webb is sensitive. In other words, Webb was made to be sensitive to the light of the first stars.
While we were waiting for the telescope to be put into orbit, astronomers did a fantastic job of mapping what are called gravitational lenses. These are areas where massive foreground objects distort space in a way that causes it to act like a lens, greatly amplifying the light from distant areas behind it. SMACS 0723 is an area where massive galaxy clusters act in concert to create a strong lens, giving us the chance to see objects from the early Universe. How early, and how small an object will we see? We'll find out on Tuesday.
Stephan’s Quintet: This should be a "before and after" target. Stephan's Quintet is a tightly packed cluster of galaxies that was first identified back in the 1800s; it has been studied intensively ever since. Other space telescopes have shown a thin shockwave in the gas between the galaxies—one that's zipping along at several million kilometers an hour. While I have no doubt that a panoramic view of the galaxies would be attractive—just look at them!—I expect we'll get a zoom-in on the filament and a comparison between those images and the ones taken by other observatories.
Southern Ring Nebula: This is an example of a planetary nebula, which has nothing to do with planets. Instead, a planetary nebula is formed when an older, massive star blasts off some of its outer layers, forming a ring of expanding gas. These nebulas are both fairly common and significant because the outer layers often contain some heavier elements that contribute to the formation of new exosolar systems. Imaging them can be helpful because we don't fully understand the processes that led to the ejection of material or the behavior of the ejected gas afterward, and the material can obscure what's happening with the star(s) that ejected it (this is the case with Eta Carinae, mentioned above).
As a bonus, the Southern Ring Nebula also happens to be gorgeous (as you can see from the image up top), and it has been imaged extensively, giving Webb's operators another chance to show off what the observatory adds compared to prior imaging. And again, the turbulent material of the ejected shell could show off Webb's ability to image fine details.
Even knowing what the targets will be, it's not clear what we'll be seeing. For pure aesthetics, several of these targets would benefit from a wide-field treatment. Yet the main benefit of the Webb will be its ability to resolve unprecedented details, which requires a lot of zooming in. So I'm excited to see whether the telescope's operators have had the time to do both or if we'll get a bit of one or the other.
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