Researcher involved in discovery of tiny star with a monstrous temper

A tiny star with ‘a monstrous temper’ has been discovered by an international team of researchers, including Dr Sarah Casewell of the Department of Physics and Astronomy.

Dr Casewell was the primary investigator in the programme that observed the star that shows evidence of much stronger flares than anything our Sun produces. If similar stars prove to be just as stormy, then potentially habitable planets orbiting them are likely to be much less hospitable than previously thought.

The research team targeted a well-known red dwarf star located about 35 light-years from Earth in the constellation Boötes. The object is so small and cool that it is right on the dividing line between stars (which fuse hydrogen) and brown dwarfs (which do not).

One of the things that makes this small star remarkable is that it spins rapidly, completing a full rotation about every 2 hours.

The researchers examined the star with the new Atacama Large Millimeter/submillimeter Array (ALMA) and detected emission at a frequency of 95 GHz. 

Previous data from the Karl G. Jansky Very Large Array in Socorro, NM showed that this star has a magnetic field several hundred times stronger than our Sun. This puzzled astronomers because the physical processes that generate the Sun’s magnetic field shouldn’t operate in such a small star.

Dr Sarah Casewell

Dr Casewell said: “This object is one of the best known radio emitting ultracool dwarfs and this is the first time it has been detected at such a high frequency. Our detection of the flares with ALMA really shows just how active this object is."

This is the first time that flare-like emission at such high frequencies has been detected from a red dwarf star. What's more, the emission from this star is 10,000 times brighter than what our own Sun produces, even though it has less than one-tenth of the Sun's mass. The fact that ALMA detected this emission in a brief 4-hour observation suggests that the red dwarf is continuously active.

This has important implications for the search for habitable planets outside the Solar system. Red dwarfs are the most common type of star in our galaxy, which makes them promising targets for planet searches. But because a red dwarf is so cool, a planet would have to orbit very close to the star to be warm enough for liquid water to exist. That proximity would put the planet right in the bull’s-eye for radiation that could strip its atmosphere or destroy any complex molecules on its surface.