Exoplanets that venture near their host stars are doomed to premature deaths – even before they get close enough to be ripped apart by the stars' gravity, two new studies suggest.
A star's gravity can put a nearby planet on a 'fast track' to spiralling into the star and may also cause the planet to lose much of its atmosphere, the studies say. The research may help explain why few exoplanets have been found right next to their host stars.
More than 300 exoplanets have been catalogued to date. Many are situated close to their host stars, where it is thought to be too hot for gas and dust to collapse into planets in the first place. That implies that the planets came from farther away and migrated inwards.
But strangely, the closest-in ones are commonly found some 0.05 astronomical units (AU) from their host stars (1 AU is the distance from the Earth to the sun). This distance, which corresponds to a three-day orbit around a star as heavy as the sun, is sometimes called the "three-day pile-up".
No one is sure why the planets seem to pile up there. Very close to a star, at a boundary called the Roche limit, planets are dismembered by the star's gravity. But the migration of planets seems to stop well outside this limit.
A star's gravity can put a nearby planet on a 'fast track' to spiralling into the star and may also cause the planet to lose much of its atmosphere, the studies say. The research may help explain why few exoplanets have been found right next to their host stars.
More than 300 exoplanets have been catalogued to date. Many are situated close to their host stars, where it is thought to be too hot for gas and dust to collapse into planets in the first place. That implies that the planets came from farther away and migrated inwards.
But strangely, the closest-in ones are commonly found some 0.05 astronomical units (AU) from their host stars (1 AU is the distance from the Earth to the sun). This distance, which corresponds to a three-day orbit around a star as heavy as the sun, is sometimes called the "three-day pile-up".
No one is sure why the planets seem to pile up there. Very close to a star, at a boundary called the Roche limit, planets are dismembered by the star's gravity. But the migration of planets seems to stop well outside this limit.
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