New Neptune-like planet could be giant water world

A newly discovered planet enveloped in water could answer some of the mysteries of our solar system, say Nasa scientists.

HAT-P-26b, which sits 430 light years from Earth, is similar in size to Neptune, our solar system's fourth largest planet, but is primarily a rocky core covered in water.

However, rather than being a full ocean world, its 700C temperature means the liquid is vapour.

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"It's going to be like Washington D.C. on a really horrible summer day," joked the LA Times.

The planet's "primitive, watery atmosphere" suggests it formed "either near its star, or relatively late in the time of its solar system", The Independent says.

Experts hope studying HAT-P-26b's peculiar features and learning how it came to be formed could help them crack how the solar system itself came into existence.

Hannah Wakeford, at Nasa's Goddard Space Flight Center, told New Scientist: "We really need to learn how other solar systems can form in order to put our own solar system in context.

"What we're trying to learn ultimately is how easy it is to form a solar system like our own."

Professor David Sing, from the University of Exeter, said the "exciting new discovery" felt like a "big breakthrough" in the quest to "learn more about how solar systems are formed and how it compares to our own".

More than 3,000 exoplanets have been discovered, but it can be challenging to learn about their atmospheres. Experts hope the James Webb space telescope, which launches next year, will get to the bottom of even more mysteries by analysing further planetary atmospheres.