First glimpse into the core of a planet

The surviving core of a planet has been discovered orbiting a distant star by a team of academics, including University of Leicester astronomers, offering the first ever glimpse inside of a planet.

Published today in the journal Nature, it is thought that this is the first time an exposed core of a planet has been observed, offering the unique opportunity to see inside its interior and learn about its composition.

Discovered to be the same size as Neptune in our own solar system, the core - named TOI 849 b - is believed to be a planet that was either stripped of its gaseous atmosphere or that failed to form one in its early life.

Dr Sarah Casewell, Science and Technology Facilities Council Ernest Rutherford Fellow at the University of Leicester said: “This is the first time that we’ve discovered an intact exposed core of a gas giant around a star. This planet has half the mass of Saturn but with a similar density to the Earth – what we’re seeing isn’t a gas giant like Saturn, but the rocky core of the planet. This is the first time we have detected a planet like this, and it will be a really important target for future observations as the remnant atmosphere will give us clues into the planet’ s formation.”

The core is located approximately 730 light years away and orbits within the ‘Neptunian desert’ – a term used by astronomers for a region close to stars where we rarely see planets of Neptune’s mass or larger.

It was found in a survey of stars by NASA’s Transiting Exoplanet Survey Satellite (TESS), using the transit method: observing stars for the tell-tale dip in brightness that indicates that a planet has passed in front of them.

Researchers determined that the object’s mass is 2-3 times higher than Neptune but it is also incredibly dense.

The research was undertaken by a team including academics from the University of Warwick and the University of Leicester.

• A remnant planetary core in the hot Neptunian desert