NASA-ESA's Webb telescope to uncover mysteries of sub-Neptunes; Here's how

The James Webb Space Telescope, which is nearing its launch scheduled on December 18, already has a gamut of subjects that are waiting to be explored. As the latest addition to the list, NASA revealed that the Webb telescope will lift the shroud of mystery from sub-Neptunes, the most common and the least known class of planets in the universe. Sub-Neptunes are basically the planets that are bigger than the Earth, smaller than Neptune and orbit their star at a closer distance than Mercury orbits the sun. Until now, scientists have been able to determine basic properties such as size, mass, and orbit of hundreds of these planets, however, it is their fundamental nature that still remains unclear. 

Here’s how the Webb telescope plans to solve the sub-Neptune mystery

According to NASA scientists, the key to figuring out what sub-Neptunes are made of and how they formed is examining their atmospheres. A technique known as transmission spectroscopy is the most effective method of analyzing the atmospheres of exoplanets. NASA explains, “When the planet is transiting its star, some wavelengths (colors) of starlight are filtered out by gases in the planet’s atmosphere. Because each type of gas has a unique “signature,” or set of wavelengths that it absorbs, it’s possible to figure out what an atmosphere is made of based on patterns in the transmission spectrum.”

However, this technique has only been useful for exoplanets other than sub-Neptunes due to a common haze problem on the latter class of planets. Eliza Kempton of the University of Maryland–College Park said as per NASA, “There have been very few atmospheric observations of sub-Neptune planets. And most of those have been dissatisfying in that the spectra have not revealed much in the way of spectral features that would allow us to identify the gases in the atmosphere." With Webb, the most powerful telescope ever built, researchers are confident that they will get a much clearer view of sub-Neptunes through their atmospheres. 

In order to solve the sub-Neptune mystery, the Webb telescope has two exoplanets-  the Sub-Neptune dubbed GJ 1214 b and hot Sub-Neptune TOI-421 b. The GJ 1214 b is a warm sub-Neptune orbiting a nearby red dwarf star. Scientists plan to observe this planet using the Webb telescope’s Mid-infrared instrument (MIRI) for 50 hours. They will wait till the planet completes a little more than one full orbit and then they will then analyze the data in three different ways to narrow down the possible combinations of gases and aerosols that make up GJ 1214 b’s atmosphere. The GJ 1214 b is an exoplanet whose aerosols could be similar to those that make up smog-like haze found on Saturn’s moon Titan.

 NASA says that they have selected the hot Sub-Neptune TOI-421 b to test this hypothesis. The scientists will observe TOI-421 b twice as it transits its star, once using Webb’s Near-Infrared Imager and Slitless Spectrograph (NIRISS) and again with the Near-Infrared Spectrograph (NIRSpec), to produce a complete near-infrared transmission spectrum of the planet. “If the hypothesis is correct and TOI-421 b’s skies are clear, the spectrum can be used to measure the abundance of molecules like water, methane, and carbon dioxide. If it turns out that TOI-421 b has an aerosol problem, the team will use the data to better understand what those aerosols are made of,” NASA said in its statement.

(Image: Twitter/@NASAWebb)