At just over 10 light years away, e (epsilon) Eridani is one of the closest stars to the Sun. As such, it has long been seen as a tempting target for extrasolar-planet spotters. Such searches have so far proved fruitless, but a report in Astrophysical Journal Letters provides suggestive evidence that this star just might have a family of planets.

J. S. Greaves of the Joint Astronomy Centre in Hilo, Hawaii and colleagues imaged e Eridani at submillimetre wavelengths using a new instrument called SCUBA (short for 'Submillimetre Common-User Bolometer Array) at the James Clerk Maxwell telescope on Mauna Kea, Hawaii. They found the star surrounded by a doughnut-shaped disk of dust, at its thickest around 60 astronomical units (AU, where one AU is the distance between Earth and Sun) from the star. This resembles the so-called 'Kuiper Belt' of comets and other débris at a similar distance around the Sun.

Disks around other stars are almost commonplace findings nowadays, but the feature circling e Eridani is intriguing for reasons apart from its mere existence. First, there seems to be a significant amount of dust within the ring itself – between the peak at 60 AU and the star itself. The environment around the star is much dustier than that around the Sun. This fits with other evidence that the star is young: between 500 million and a billion years old, or between a fifth and a tenth the age of the Sun. A dusty environment suggests collisions between planets and asteroids, corresponding to the 'period of heavy bombardment' in the early history of our own Solar System, in which impacts gouged the Moon from the Earth, and created the Moon's major impact basins.

Second, the disk is not perfectly smooth, but denser and brighter on one side than the other. The most likely explanation for this is the gravitational perturbation of a large planet (corresponding, perhaps, to Neptune) orbiting on the inside edge of the dust ring, or within it.

The researchers are quick to stress that they have not actually discovered a planet or planets around this star. They do, however, advance the e Eridani system as a model for what our own Solar System looked like in its youth. This would be a valuable contribution towards answering an abiding question in planetary science – that is, how typical is our own Solar System of planetary systems as a whole? The current slew of planetary detections is biased, by the methods used, to finding giant planets orbiting very close to their parent stars. No such planets exist in our own Solar System, raising the question of whether our own family of planets is atypical.

On the other hand, dust rings have been found around stars rather different from our Sun – very hot, bright and fast-burning, such as Vega (the star – literally – in the film Contact), or 'protostars' – bodies yet to ignite fully as stars. Although epsilon Eridani is smaller than the Sun and only a third as luminous, it is perhaps sufficiently like the Sun for sensible comparisons to be made.