Using the Hubble space telescope, astronomers have discovered water vapor in the atmosphere of a small exoplanet. “Water on such a small planet is a groundbreaking discovery,” said Laura Kreidberg from the Max Planck Institute for Astronomy (MPIA) in Heidelberg. “It brings us closer than ever before to characterizing truly Earth-like worlds.”
The planet, called GJ9827d, is 97 light-years away and is just twice the size of Earth. A light year is the distance that light travels in one year – a distance of 9.46 trillion kilometers.
According to the researchers, it is the smallest exoplanet where water vapor has been detected in the atmosphere to date. However, it is still unclear whether it is a small amount of water vapor in the atmosphere or whether it consists mainly of water.
“Any result would be exciting”
The observation program was developed with the aim of not only detecting molecules in the planet’s atmosphere, but also specifically searching for water vapor, explained Pierre-Alexis Roy from the University of Montreal in Canada. “Any result would be exciting, whether water vapor dominates or is just a small component of a hydrogen-dominated atmosphere.”
With a Venus-like temperature of 400 degrees, the planet would definitely be an inhospitable, humid, hot world if the atmosphere consisted predominantly of water vapor, say experts. There are currently two possibilities: Either the planet clings to a hydrogen-rich shell – similar to a small Neptune. Or it consists of 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. “Hopefully we can now settle the question of water worlds once and for all.”
