Water found in hottest planet orbit

The “hot Jupiter” planet’s surface temperatures exceed 900C.

Writing in the journal Nature, the scientists say their discovery may help find planets that can support life.

In a separate study, the US space agency (Nasa) says it has found carbon dioxide in the atmosphere of the same planet.

Molten core

The planet known as HD 189733b is classed as a hot Jupiter due to its fiery molten centre and heavily gaseous atmosphere, which mimics the atmosphere of Jupiter, the gas giant in our own solar system.

The generation of heat by the planet’s core provides the key to why scientists have been able to identify water vapour in its atmosphere.

Gases in the planet’s atmosphere modify the wavelengths of heat radiation coming from the planet’s hot surface. These wavelengths can be detected by space telescopes such as Hubble or the Sun-orbiting Spitzer telescope used in this study.

The type of gas present in the planet’s atmosphere can be determined by looking at the spread of infrared radiation reaching the telescope, each gas producing a different wavelength.

Dr Drake Deming from Nasa’s Goddard Space Flight Center, Maryland, US, has looked for signs of water on similar gas giants in the past. He says water vapour in the atmosphere leaves an unmistakeable signal.

“It produces a unique fingerprint, water vapour modulates the shape of the radiation in a very characteristic way.