ESA scientists help to 'shortlist' stars for planetary exploration
A scientist working at the European space agency (ESA) has discovered a way to 'shortlist' stars that might have planets for future exploratory missions in space. Markus Landgraf and colleagues found the first direct evidence that a bright disc of dust surrounds our solar system. The finding may help astronomers to determine which other stars in the galaxy are most likely to harbour planets, and allows mission planners to draw up a 'shortlist' of stars to be observed by ESA's future planet-search missions, Eddington and Darwin. The discovery of the dust ring around the solar system strengthens the idea that they signal planetary systems when observed around mature stars. This is because planetary systems are thought to condense from a cloud of gas and dust, with planets forming near the central star where the material is at its most dense. However, far away from the star, the material is thinly spread and comes together to form a vast band of dust and gas. In our solar system, these bodies form the Edgeworth-Kuiper dust belt that extends out beyond the orbit of the planet Neptune. Normally, this dust is either incorporated into larger celestial bodies or ejected from the solar system. For the band still to be present today means that something must still be replenishing it. Marcus Landgraf explains that 'in order to sustain such a ring, 50 tonnes of dust have to be generated every second.' 'If you have a dust ring around a star that's not particularly young,' explained ESA Darwin scientist Malcolm Fridlund, 'then it's interesting because the dust has to come from somewhere. The only explanation is that the star has planets, comets, asteroids or other bodies that collide and generate dust.' The result will help scientists searching for extra-solar planets to draw up a list of target stars.