The Webb telescope could unleash the search for life by studying inhospitable hell worlds

Now that It has started scientific operations, some of the most important targets for the James Webb Space Telescope will be exoplanets. The telescope can identify and study planets outside our solar system and even look into their atmospheres to see what they are made of. This will give us more information than ever about the variety of planet types out there.

If you look at data on exoplanets that have been studied in the past and will be studied in the future, you will see that many of them are of a type called Hot Jupiter. Unlike rocky planets like Earth, Mars, or Venus, hot Jupiters are gas giants that orbit very closely to their host stars. With a year on a hot Jupiter lasting only a few days or even just a few hours, they are close enough to their stars to experience very high temperatures of thousands of degrees Celsius. And their mass varies from slightly lighter than Jupiter to more than 10 times its mass.

As strange as these planets sound — and as different as they are from anything in our solar system — examining them could be crucial in learning how planetary systems form. Scientists are still unsure how hot Jupiter will get, as they appear to be orbiting too close to their stars to have formed there. Perhaps they formed farther out and were then pulled into a tighter orbit, or perhaps tidal forces influenced their orbits. We don’t know exactly.

Another reason to study these planets is that they tend to be bloated as they have the mass of a planet but can reach the size of a star. When a planet has a bloated atmosphere, it’s easier to get data about that atmosphere using spectroscopy, where light coming from the star goes through the atmosphere and is analyzed to see what that atmosphere is made of.

One such bloated, hot Jupiter is WASP-121b, a monster planet with a temperature in excess of 2000 degrees Celsius. “It has a very pompous, pompous vibe. And it also has a very clear atmosphere because it’s too hot for clouds and haze to form, making it a very tempting target for transmission spectroscopy because there’s a lot of atmosphere for the parent star’s light to shine through.” , explained Steph Merritt of Queen’s University Belfast, who studied the planet using a method called Doppler spectroscopy, in a presentation at the 2022 National Astronomy Meeting.

However, studying the atmosphere of a planet millions of kilometers away is not easy. Previous work on exoplanet atmospheres has been done by both ground-based telescopes and Hubble, but there are limits to how much these tools can tell us. For example, Hubble was used to study the atmosphere of hot Jupiter WASP-17b, but the observations only captured part of the transit (the period when the planets pass in front of the star, making spectroscopy possible).

This complicates data analysis, as there is great uncertainty about what specific elements make up the atmosphere of WASP-17b. “All we can really say for sure about WASP-17b is that the current data show a confident direction for H2O and a cautious hint for CO2,” said Lili Alderson of the University of Bristol, who is involved in a reanalysis of data worked on the planet, at the same session.

WASP-17b will be one of the first targets James Webb will study in his first year, which will help reveal more about its atmosphere by collecting more infrared data in addition to the optical data collected by Hubble. “We need the combination of high-quality optical and infrared data to properly understand the atmospheres of these planets,” Alderson said.

An example of the oddity of hot Jupiters is that many of them exhibit a phenomenon called inverted atmospheres, in which temperatures in the upper atmosphere increase with altitude. You would expect the atmospheres to get cooler the higher you go – unless you have a special situation like the Earth’s ozone layer. The current theory is that the metallic elements found in hot Jovian atmospheres, such as titanium oxide, vanadium oxide, and iron hydride, absorb the star’s light and warm the atmosphere in a similar way to our ozone layer.

As much as astronomers have learned about hot Jupiters so far, there is still much more to learn from James Webb. If we can figure out how these strange planets formed, we can learn more about the formation of other systems, including our own solar system. But even with this additional data, it may not be enough to fully understand this strange and alien world.

“Planets are really complicated!” said Alderson. “We can’t always draw bold and exciting conclusions from a simple data set.”