Telling Star Age with Sound Alone

If you listen closely, can you hear a star age? Probably not. But researchers do say that sound waves all on their own can help experts distinguish young stars from adolescent ones.

According to a study recently published in the journal Science, researchers at KU Leuven's Institute for Astronomy determined that they could measure the age of a young star by gathering data on acoustic vibrations.

Interestingly, these vibration are detected and measured using ultrasound technology similar to that used in the field of medicine to look at unborn children - fitting as the researchers were trying to get a closer look at the states of infant stars.

The astronomers looked at 34 stars in all, aged under 10 million years old and sized up to four times the size of the Sun.

"Our data shows that the youngest stars vibrate slower while the stars nearer to adulthood vibrate faster. A star's mass has a major impact on its development: stars with a smaller mass evolve slower. Heavy stars grow faster and age more quickly," first author Konstanze Zwintz explained in a statement.

According to the study, acoustic vibrations are produced by radiation pressure inside stars. Infant stars tend to be less compact that adolescent ones because the process that forms stars involves the contracting of clouds of dust and gas around a singular gravitational pull within a star "nursery." The contracting mass of dust, gases, and resulting radiation grows denser and hotter until the core temperature is sufficient to start nuclear burning of hydrogen - producing increased radiation pressure and faster resulting vibrations. Once this radiation pressure stabilizes, the star is considered an "adult."

"We now have a model that more precisely measures the age of young stars," Zwintz said. "And we are now also able to subdivide young stars according to their various life phases."

Past theoretical data has already argued that infant stars would vibrate slower than older ones, but this is the first physical evidence of the phenomenon.

The study was published in Science Express on July 3.