Swiss Astronomers Discover New Kind of Variable Star in Stellar Cluster

A team of Swiss astronomers have accomplished an extraordinary feat. They've discovered a new class of variable stars by measuring minute variations in stellar brightness. The new findings could allow researchers to understand a little bit more about our universe and allow them to make more precise calculations about stellar phenomena.

Many stars are known as variable or pulsating stars because their apparent brightness changes over time. How this brightness changes, though, largely depends on the properties of their interiors. This complex process is still being studied by scientists and has created a whole branch of astrophysics called asteroseismology. In this branch of science, astronomers actually "listen" to stellar vibrations in order to probe the physical properties of the stars and learn a little bit more about their inner workings.

In this particular case, though, the researchers made regular measurements of the brightness of more than three thousand stars in the open star cluster NGC 3766 over the course of seven years. Located about 7,000 light-years from Earth, this star cluster is estimated to be about 20 million years old.

So what did the researchers find? They found that 36 of the cluster's stars followed an unexpected pattern; these stars had tiny regular variations in their brightness at the level of .1 percent of the stars' normal brightness. These variations had periods between about two and 20 hours. The researchers had, in fact, discovered a new class of variable stars.

"The very existence of this new class of variable stars is a challenge to astrophysicists," said Sophie Saesen, one of the team members, in a news release. "Current theoretical models predict that their light is not supposed to vary periodically at all, so our current efforts are focused on finding out more about the behavior of this strange new type of star."

While these stars are relatively unremarkable aside from this variability, they do have one unique property. The stars seem to be fast rotators, whirling at speeds that are more than half of their critical velocity, which is when stars become unstable and throw off material into space. This fast spin, in particular, could explain the variability that the astronomers saw.

Currently, the researchers are investigating these stars a bit further. They hope that in the future, they'll be able to explain the reason behind their apparent changes in brightness.

The findings are published in the journal Astronomy & Astrophysics.