Mechanisms of nearby star uncovered

Astronomers from the Harvard-Smithsonian centre have discovered our neighbouring star, Proxima Centauri, has more in common with our Sun than previously thought.

A small red dwarf, it is orbited by an Earth-sized planet — Proxima b. It is one-tenth the size of the Sun and researchers have discovered it has a regular cycle of starspots, just like our Sun.

Jeremy Drake, from the Smithsonian and co-author of the paper published in Monthly Notices of the Royal Astronomical Society, said: “The existence of a cycle in Proxima Centauri shows that we don't understand how stars' magnetic fields are generated as well as we thought we did.”

Our Sun has an 11 year activity cycle of starspots beginning with an almost spot-free surface to having more than 100 sunspots but on less than one percent of the Sun’s surface. Proxima Centauri undergoes a similar cycle but it is four years shorter – and much more dramatic. At least one-fifth of its surface is covered in spots at once, with some starspots much larger than those appearing on the Sun’s surface.

This discovery surprised astronomers as its interior is very different from the Sun’s. The outer third of the Sun experiences convection motion while the inner two-thirds remain, comparatively, still. Astronomers think the change in the speed of rotations is responsible for starspots. It is thought Proxima’s interior is convective all the way to its core and therefore shouldn’t have a regular starspot cycle.

Lead author, Brad Wargelin from the Smithsonian Center, said: “If intelligent aliens were living on Proxima b, they would have a very dramatic view.”

Although the scientists did not try to address the potential viability of life on Proxima b, which exists in the star’s habitable zone an existing theory suggests flares or a stellar wind have stripped away the planet’s atmosphere. This would mean Proxima b is more similar to the Moon than planet Earth.