Roasted planet remains give hint of what lies in store for Earth

ASTRONOMERS have identified two roasted Earth-size planets that survived being engulfed by a swollen dying star.

The planets are the burned-out remnants of what were once giant Jupiter-like worlds, scientists believe.

The discovery, reported in the journal Nature, provides a sobering reminder of what lies in store for the Earth billions of years from now.

When the sun reaches the end of its life in about five billion years it will grow into a red giant big enough to swallow up all the innermost planets of the solar system.

Earth will be vaporised in the inferno and all life on it destroyed.

The two newly detected planets only escaped the same fate by being so large.

Named KOI 55.01 and KOI 55.02, they circle very close to their parent star, which has passed the red giant stage, lost nearly all its outer layers, and shrunk to a hot cinder core.

The distant star, known as a subdwarf B star is almost 4,000 light years away.

Astronomers stumbled on the planets by accident while studying data from the American space agency Nasa’s Kepler space telescope.

They had been investigating pulsating stars affected by rhythmic expansions and contractions caused by pressure and gravitational forces.

Two blips in the light signals from the subdwarf B star KIC 05807616, betrayed the presence of the planets passing close in front of it.

Dr Elizabeth Green, from the University of Arizona’s Steward Observatory, who took part in the research, said: “When our sun swells up to become a red giant, it will engulf the Earth.

“If a tiny planet like the Earth spends one billion years in an environment like that, it will just evaporate.

“Only planets with masses very much larger than the Earth, like Jupiter or Saturn, could possibly survive. Planets this close to their star are tidally locked, meaning the same side always faces the star, just like the same face of the moon always faces the Earth.

“The day side of Mercury is hot enough to melt lead, so you can imagine the harsh conditions on those two small planets racing around a host star that is five times hotter than our sun at such a close distance.”

The tight orbits meant the planets must have been engulfed when their host star swelled up into a red giant.