NASA’s James Webb Space Telescope (JWST) has unveiled an entirely new type of exoplanet shrouded in hot water vapor. The planet, designated GJ 9827 d, is located roughly 100 light-years from Earth and is the first observed example of a “steam world,” a category long theorized by astronomers but never before confirmed.
World of Steam and Vapor
GJ 9827 d, around twice the size of Earth and three times its mass, possesses an atmosphere that is almost entirely composed of water vapor. While scientists have previously hypothesized the existence of such steam-covered planets, this discovery marks the first observational evidence of such a world.
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“This is the first time we’re ever seeing something like this,” said Eshan Raul, a member of the research team and a doctoral student at the University of Wisconsin-Madison. The planet’s atmosphere of hot water vapor earned it the nickname of a “steam world,” though scientists are quick to point out that this exotic environment would be inhospitable to life as we know it.
Search for Water Worlds
The discovery of GJ 9827 d is significant not only because it represents a new type of exoplanet, but also due to the method used to observe it. The research team, led by Caroline Piaulet-Ghorayeb from the University of Montréal’s Trottier Institute for Research on Exoplanets, employed a technique known as transmission spectroscopy to detect the steamy atmosphere. This method analyzes the light from a star as it passes through a planet’s atmosphere, allowing researchers to determine its composition based on how the atmosphere absorbs light.
Through this technique, the team discovered that GJ 9827 d’s atmosphere is rich in heavy molecules, a significant finding that distinguishes this exoplanet from others. Most exoplanets of similar size have atmospheres dominated by lighter elements like hydrogen and helium, but GJ 9827 d’s atmosphere is more akin to that of Earth, suggesting it may contain heavier molecules such as water.
“This is a crucial step in understanding the atmospheres of exoplanets between the size of Earth and Neptune,” said study co-author Ryan MacDonald, an astrophysicist at the University of Michigan. “It moves us closer to detecting atmospheres on planets that might be habitable.”
Step Toward Finding Habitable Worlds
While GJ 9827 d’s extreme, steamy environment is unlikely to support life, it offers valuable insights for astronomers studying other potentially habitable exoplanets. According to Raul, studying planets like GJ 9827 d can help researchers understand the conditions on small exoplanets that might be more suitable for life.
“There could be many more planets like this out there,” said Raul. “If these water worlds really exist, it makes you wonder what else is out there that we haven’t discovered yet.”
New Frontier in Exoplanet Research
The JWST’s ability to peer into the atmospheres of distant worlds represents a major leap forward in the study of exoplanets. GJ 9827 d is just one of many exciting discoveries made by the telescope since it began its mission. In this case, the JWST’s sensitivity allowed researchers to confirm not only the presence of water vapor but an atmosphere dominated by heavier molecules—an unprecedented observation.
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For Raul and other young researchers, this discovery signals an exciting time in astronomy. “Being able to work with data from the most powerful telescope ever made, at this point in my career, is incredible,” Raul said. “There’s never been a better time to get into astronomy.”