Before finding the first planet outside of our solar system in 1992, scientists were able to identify the first black hole, detect the remnants of the Big Bang, and take pictures of many distant galaxies. This was because finding exoplanets was once so difficult. Many planetary scientists got their start in the field long before exoplanet astronomy was even a thing.
However, as of this now, astronomers have discovered far over 5,000, and they are still finding more (SN: 3/22/22). It’s easy to forget how little we still know about these far-off worlds given the constant flow of discoveries. The vibrant oceans, clouds, and volcanoes seen in artists’ representations are speculative dreams frequently sparked by the mass, radius, and distance from the star that scientists know about most worlds.
However, exoplanets are becoming more and more visible to the James Webb Space Telescope (SN: 10/6/21). Launched by the end of 2021, the telescope is being used by scientists to investigate the atmospheres of hundreds of worlds, ranging from rocky worlds roughly the size of Earth to gas giants.
Starlight travels through an exoplanet’s atmosphere as it round its star, and depending on the gases in the atmosphere, light at particular wavelengths is absorbed. This leaves traces in the starlight spectrum that can be used by scientists to identify the compounds that the light traveled through. JWST has previously found water, carbon dioxide, methane, and other elements on other worlds because it is sensitive to infrared wavelengths, which are where these traces are highest.
Laura Kreidberg of the Max Planck Institute for Astronomy at Heidelberg, Germany, says she is frequently asked one specific question on what she believes JWST might uncover in light of these detections.
Finding evidence of extraterrestrial life is quite exciting, she says. “And that excites me as well.” However, she continues, before scientists can confidently identify life on other planets, they still have a lot to learn about planets. Furthermore, the telescope’s field of view will mostly be limited to exoplanets that are extremely large, extremely hot, or both—conditions that are not believed to be conducive to life due to technical restrictions.
The eight planets in our solar system account for the majority of what we currently know about exoplanets. The anticipated 10-year lifespan of JWST could provide significant insights, perhaps addressing basic inquiries such as the composition and formation of exoplanets, as well as whether our solar system is an anomaly in our galactic neighbourhood (SN: 5/11/18).
These are the five major planetary riddles that JWST is intended to help scientists solve.
Why do some rocky planets have atmospheres and others don’t?
A rocky planet needs an atmosphere in order to support life. However, the factors that ultimately decide whether a rocky body can cling to a gaseous outer shell remain a mystery to scientists.
In order to distinguish between worlds with and without atmospheres, astronomers are looking for what they refer to as the “cosmic shoreline.” In 2017, researchers discovered that our solar system has a shoreline that is determined by the equilibrium between the solar radiation that a planet or moon gets and the gravitational pull on its surface. While atmospheric gases are held firmly to the earth by gravity, sunlight gives gas particles the energy they need to escape from the upper atmosphere.
In order to investigate the possibility that this kind of cosmic seashore is present throughout the galaxy, scientists must determine which exoplanets are home to atmospheres. Although it seems like a very simple inquiry, JWST has just recently made it feasible to provide an answer.
Astronomer Renyu Hu of NASA‘s Jet Propulsion Laboratory in Pasadena, California, claims that he and his associates have resolved the atmospheric controversy surrounding 55 Cancri e, a planet located around 40 light-years away from Earth orbiting a sun-like star (SN: 11/18/07). Super-Earth 55 Cancri e (SN: 5/11/15) is slightly larger than Earth but significantly smaller than Neptune. Hu and colleagues provide JWST findings in an article that was published on May 8 in Nature, indicating that the atmosphere of 55 Cancri e is composed of either carbon monoxide, carbon dioxide, or a combination of the two plus nitrogen. It’s the first time an atmosphere enveloping a rocky, terrestrial exoplanet has been discovered.
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