Hubble Finds Three, Surprisingly Dry Jupiter-Like Exoplanets

Astronomers, who used NASA’s Hubble Space Telescope to look for water vapor in the atmosphere of three exoplanets, have found that the trio, orbiting stars similar to the sun, are surprisingly dry.

Astronomers previously believed that the three exoplanets, dubbed HD 189733b, HD 209458b and WASP-12b, were ideal candidates for harboring water vapor in their atmospheres. However, the planets, which have temperatures ranging between 1,500 degrees to 4,000 degrees Fahrenheit, were found to have very little water, compared to the amount predicted by standard planet-formation theories.

“Our water measurement in one of the planets, HD 209458b, is the highest-precision measurement of any chemical compound in a planet outside our solar system, and we can now say with much greater certainty than ever before that we've found water in an exoplanet,” Nikku Madhusudhan of the Institute of Astronomy at the University of Cambridge, England and the study’s lead author, said in a statement. “However, the low water abundance we have found so far is quite astonishing.”

The three exoplanets, also known as “hot Jupiters” are located between 60 and 900 light-years away from Earth. Astronomers believe that the new results, published Thursday in The Astrophysical Journal Letters, could have major implications in the search for water on potentially inhabitable Earth-sized exoplanets.

“We have to revisit planet formation and migration models of giant planets, especially ‘hot Jupiters,’ and investigate how they're formed,” Madhusudhan said. “We should be prepared for much lower water abundances than predicted when looking at super-Earths.”

In order to determine the amount of water vapor in each of the planet's atmospheres, the astronomers used Hubble to observe the planets’ near-infrared spectrum, NASA said, adding that detecting water on transiting planets is almost impossible from the ground because of the amount of water in Earth's atmosphere, which contaminates the observation.

“There are so many things we still don't know about exoplanets, so this opens up a new chapter in understanding how planets and solar systems form,” Drake Deming of the University of Maryland, said in the statement. “The problem is that we are assuming the water to be as abundant as in our own solar system. What our study has shown is that water features could be a lot weaker than our expectations.”