“This brings us closer to characterizing Earth-like worlds than ever before,” says Laura Kreidberg of the Max Planck Institute for Astronomy (MPIA) in Heidelberg. The planet, called GJ9827d, is 97 light-years away from us and is twice the size of Earth.
A light year is the distance that light travels in one year, which is 9.46 trillion kilometers. According to researchers, it is the smallest exoplanet on which water vapor has been detected in the atmosphere so far. However, it is still unclear whether it is a small amount of water vapor in the atmosphere or whether it is mainly composed of water.
“An inhospitable, humid, hot world.”
Pierre-Alexis Roy of the University of Montreal in Canada said that the monitoring program was developed with the aim of not only detecting molecules in the planet's atmosphere, but also looking specifically for water vapor. “Any result would be interesting, whether water vapor is dominant or it is just a small component of the hydrogen-dominated atmosphere.”
With a Venus-like temperature of 400 degrees, the planet would certainly be a hot, humid and inhospitable world if the atmosphere consisted mostly of water vapor, experts say. There are currently two possibilities: Either the planet is clinging to a hydrogen-rich atmosphere – similar to a mini-Neptune. Or it's half water and half rock, something like a warmer version of Jupiter's moon Europa.
In search of traces of water and other molecules, astronomers recently observed the planet GJ9827d with the James Webb space telescope. “We can't wait to see what this data reveals,” Kreidberg said. “We hope that we can now settle the matter of the Water Realms once and for all.”
