TechWater vapor discovered on distant exoplanet: Is it a mini-Neptune or a warmer Europa?

Water vapor discovered on distant exoplanet: Is it a mini-Neptune or a warmer Europa?

The exoplanet GJ 9827 d is located 97 light years away from us.
The exoplanet GJ 9827 d is located 97 light years away from us.
Images source: © NASA
6:53 AM EST, January 29, 2024

GJ 9827 d, an exoplanet akin to Neptune, was discovered in 2017. It has a diameter twice the size of Earth and is estimated to be much heavier, with a mass approximately 3.5 times that of our planet. However, this exoplanet is very distant. It orbits around the K-type star GJ 9827, a red dwarf situated 97 light-years away in the Pisces constellation.

Discovery on exoplanet GJ 9827 d

As described by Science Alert, astronomers from NASA and the European Space Agency have been observing the transitional states of the planet for several years. Using the Hubble Space Telescope instruments for wavelength analysis, they could detect water molecules in the planet's atmosphere.

The scientists who made this discovery suggest two possible scenarios: GJ 9827 d may be a "mini-Neptune" with a water-imbued, hydrogen-rich atmosphere or a warmer version of Europa, Jupiter's moon, which is known to contain twice as much water as Earth beneath its icy crust.

Planetary system around the star GJ 9827
Planetary system around the star GJ 9827© NASA

Pioneering discovery

Described as groundbreaking, the detection of water on GJ 9827 d is significant as it's the smallest exoplanet on which water has been identified.

"Planet GJ 9827 d could be half water and half rocky," said Bjorn Benneke from the Universite de Montreal, co-leader of the research. "A smaller, rocky body like this would potentially have a lot of water vapor. Until now, we haven’t been able to directly detect the atmosphere of such a small planet. We are now slowly entering into this territory."

Scientists note that habitation on GJ 9827 d isn't possible. If the planet's atmosphere is indeed rich in water, the temperatures are expected to be scorching– it is estimated that the atmosphere might resemble Venus with temperatures of around 800 degrees Fahrenheit (425 degrees Celsius).

Even though habitation isn't plausible, this discovery creates new avenues for studying GJ 9827 d, as well as searching for planets similar to Earth. The James Webb Space Telescope, which can produce high-resolution infrared images, will play a pivotal role in this process by helping to detect a wider range of atmospheric molecules, including carbon dioxide and methane.

Related content