The inner region of an exoplanetary system, where four terrestrial planets orbit a sun-like star.
In this artist's impression, the host star is running out of hydrogen in the core. It is also losing mass, which causes the planets to move further out. The perturbation of the orbits may lead to collisions that will generate large amounts of rocky debris.
Rocky material in orbit around a white dwarf star (center). Collisions turn larger material into dust, some of which then rains down on to the white dwarf.
Researchers used the Hubble Space Telescope to examine the atmospheres of more than 80 white dwarf stars within a few hundred light-years of our sun.
In this artist's illustration, several planetary systems are shown around dying stars, where collisions destroy the rocky alien worlds.