NASA’s James Webb Space Telescope pierces through haze to reveal secrets of exoplanet GJ 1214b

Astronomers have been attempting to observe GJ 1214b, an exoplanet located 40 light-years away from Earth, for over ten years. However, their efforts have been impeded by a thick layer of haze that obscures the planet, preventing detailed study of its atmosphere. The newly launched James Webb Space Telescope (JWST) from NASA has overcome this challenge by utilizing infrared technology, enabling it to observe planetary objects and features that were previously concealed by hazes, clouds, or space debris. This advancement has greatly facilitated the search for habitable planets and early galaxies.

In a groundbreaking achievement, a group of researchers utilized the JWST to investigate the atmosphere of GJ 1214b by analyzing the thermal radiation it emits while orbiting its host star. Their findings, which were recently published in the journal Nature on May 10, 2023, represent the first direct detection of light emitted by a sub-Neptune exoplanet—a classification of planets larger than Earth but smaller than Neptune.

Although GJ 1214b’s high temperatures render it inhospitable for life, the researchers discovered indications of water vapor in its atmosphere, possibly in significant quantities. Additionally, they determined that the planet’s atmosphere is predominantly composed of molecules heavier than hydrogen. Eliza Kempton, the lead author of the study and an Associate Professor of Astronomy at the University of Maryland, expressed her excitement regarding these findings, emphasizing that they mark a significant milestone in the study of sub-Neptune planets such as GJ 1214b.

Kempton stated, “I have been dedicated to unraveling the mysteries of GJ 1214b for over a decade. When we received the data for this research, we witnessed the planet’s light vanishing as it passed behind its host star. This phenomenon had never been observed before for GJ 1214b or any other planet of its class, underscoring the remarkable capabilities of the JWST.”

A ‘new light’

Sub-Neptunes are the most prevalent planetary type in our Milky Way galaxy, but none exist within our own solar system. Despite the challenges posed by the haze surrounding GJ 1214b, Kempton and her colleagues concluded that this planet offered the best opportunity to observe a sub-Neptune’s atmosphere due to its relatively bright yet compact host star.

In their study, the team focused on measuring the infrared light emitted by GJ 1214b during its approximately 40-hour orbit around its star. The transition from day to night on the planet affects the redistribution of heat across its surface, a process heavily influenced by the composition of its atmosphere. This novel research approach, known as a phase curve observation, provided valuable insights into the atmosphere of GJ 1214b.

Kempton explained, “JWST operates at longer wavelengths compared to previous telescopes, enabling us to detect the thermal radiation emitted by the planet and construct a temperature map. We finally gained a fresh perspective on GJ 1214b.”

Through the analysis of heat patterns and fluctuations, the researchers deduced that GJ 1214b’s atmosphere is not predominantly composed of hydrogen.

Potential water world?

The presence of water on GJ 1214b has been a topic of great interest among astronomers. Previous observations conducted by NASA’s Hubble Space Telescope hinted at the possibility of GJ 1214b being a water world—a term used to describe planets with a substantial water content.

The most recent data obtained from the JWST unveiled indications of water vapor, methane, or a combination of both. These substances align with a subtle absorption of light within the wavelength range examined by the JWST. Further investigations will be necessary to precisely determine the composition of the planet’s atmosphere. Nonetheless, Kempton expressed that the evidence remains consistent with the potential existence of significant amounts of water.

Based on their observations, Kempton stated, “GJ 1214b could be a water world. We believe we have detected water vapor, although it is challenging to ascertain with certainty as water vapor and methane absorption overlap. Nevertheless, we have observed this evidence on both hemispheres of the planet, which enhances our confidence in the presence of water.”

Reflecting on the findings

In addition to their findings on the planet’s atmospheric composition, the researchers also made an intriguing discovery regarding GJ 1214b’s reflectivity. Contrary to expectations, the planet’s temperature was not as high as anticipated, indicating the presence of a reflective component in its atmosphere.

This unexpected revelation has opened up avenues for further investigations, particularly in exploring the high-altitude aerosols that contribute to the haze or potentially form clouds within GJ 1214b’s atmosphere. Previously, scientists speculated that these aerosols might consist of a dark, soot-like substance capable of absorbing light. However, the newfound reflective nature of the exoplanet introduces fresh questions and complexities.

Kempton remarked, “The composition of the hazes or clouds is not what we predicted. It appears to be bright and reflective, which is both puzzling and surprising. This revelation will undoubtedly drive extensive follow-up studies as we strive to comprehend the nature of these hazes.”

Further research endeavors will be aimed at unraveling the enigma behind the unexpected reflective properties and uncovering the precise nature and composition of the hazes or clouds present on GJ 1214b.

Source: University of Maryland

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