Surprised scientists come up ‘nearly dry’ in search for water on ‘hot Jupiter’ planets


An artistic illustration of the gas giant planet HD 209458b in the constellation Pegasus (NASA/ESA/G. Bacon and N. Madhusudhan)

Astronomers tried to find water on three planets circling sun-like stars. Instead, they found a cliche: the search for water, using NASA’s Hubble telescope, has “come up nearly dry.”

That’s surprising, according to the researchers, who checked their results against currently-used models for predicting water amounts on other worlds. Those models indicated that the three planets should have a lot more water vapor in their atmospheres.

“It basically opens a whole can of worms in planet formation,” lead researcher Nikku Madhusudhan said in a statement.

However, there’s kind of an upside to the results, as Madhusudhan of the Institute of Astronomy at the University of Cambridge explained: “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.”

That’s despite the “astonishing” lack of water they detected in the first place.

“We have to revisit planet formation and migration models of giant planets. We expected all these planets to have lots of water in them,” Madhusudhan added, noting that the results will particularly impact our understanding of so-called “hot Jupiter” planets.

Those gaseous worlds orbit close to their home stars and carry temperatures between 1,500 and 4,000 degrees Fahrenheit. Naturally, researchers were looking for water vapor in the atmosphere of these planets.

Madhusudhan also urged researchers looking for water on other kinds of exoplanets (including potentially habitable ones) to lower their expectations, thanks to the results of his “hot Jupiter” study. “We should be prepared for much lower water abundances than predicted when looking at super-Earths (rocky planets that are several times the mass of Earth),” he said.

The study is hardly the only total downer for alien enthusiasts this month: two Penn State scientists recently debunked the discovery of a “Goldilocks” planet orbiting a relatively nearby star. As it turns out, the “planet” was simply an illusion caused by the dwarf star itself.

They also disproved the existence of a second, possibly habitable planet.

Oh well. At least there are still a lot more potential exoplanets to examine.

Abby Ohlheiser is a general assignment reporter for The Washington Post.
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