A new type of planet has been discovered beyond our Solar System – a burning liquid ball of lava where temperatures reach 1,500°C.
The exoplanet, known as L 98–59 d, stores large amounts of sulphur deep within a permanent ocean of magma.
This releases copious amounts of hydrogen sulphide gas into its atmosphere, meaning the planet absolutely reeks of rotten eggs.
And its discovery suggests the diversity of worlds in our galaxy is much greater than previously thought.
The discovery was made by scientists at the University of Oxford, who used the James Webb Space Telescope (JWST) along with ground–based observatories to analyse the celestial object.
They found that the planet has an especially low density given its size, which is about 1.6 times that of Earth.
Until now, astronomers would have placed a planet like this into one of two familiar categories – either a rocky ‘gas–dwarf’ with an atmosphere of hydrogen, or a water–rich world made of deep oceans and ice.
But the new findings show it appears to belong to an entirely different class of planet boasting a global magma ocean extending thousands of kilometres below its surface.
Here, the molten planet (front left) can be seen orbiting a red star about 35 light–years from Earth
This vast molten reservoir allows the planet to store extremely large amounts of sulphur deep within its interior and maintain high levels of the smelly chemical in the atmosphere.
‘Our computer models simulate various planetary processes, effectively enabling us to turn back the clock and understand how this unusual rocky exoplanet, L 98–59 d, evolved,’ Dr Richard Chatterjee, one of the study authors, said.
‘Hydrogen sulphide gas, responsible for the smell of rotten eggs, appears to play a starring role there.
‘Further investigation may yet show that rather pungent planets are surprisingly common.’
The planet, which orbits a small red star about 35 light–years from Earth, is about five billion years old, the researchers said.
The findings, published in the journal Nature Astronomy, could indicate the diversity of worlds in our galaxy may be even greater than previously imagined.
‘This discovery suggests that the categories astronomers currently use to describe small planets may be too simple,’ lead author Dr Harrison Nicholls said.
‘While this molten planet is unlikely to support life, it reflects the wide diversity of the worlds which exist beyond the Solar System. We may then ask: what other types of planet are waiting to be uncovered?’
The researchers believe temperatures on exoplanet L 98–59 d, a burning liquid ball of lava, reach 1,500°C
Further insights into how magma oceans behave could inform us about our own world history, the team explained.
That’s because all rocky planets – including Earth – begin life this way.
‘What’s exciting is that we can use computer models to uncover the hidden interior of a planet we will never visit,’ co–author Professor Raymond Pierrehumbert said.
‘Although astronomers can only measure a planet’s size, mass and atmospheric composition from afar, this research shows that it is possible to reconstruct the deep past of these alien worlds – and discover types of planets with no equivalent in our own Solar System.’
