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Ultrasound monitors the 'heartbeats' of baby stars
Determining the age of stars has long been a challenge for astronomers. In experiments published in the journal Science,
researchers at KU Leuven's Institute for Astronomy show that 'baby'
stars can be distinguished from 'adolescent' stars by measuring the
acoustic waves they emit.
Stars are often born in clusters, the result of contracting molecular
clouds of gas and dust particles. As a star evolves from infant to
adolescent, gravitational pull causes it to contract. It gets smaller in
size and hotter until the core temperature is sufficient to start
thermonuclear fusion. At this point, the star stabilizes and becomes an
'adult'. It stays this way for vast tracts of time.
Determining the age of a young star is far from simple, and knowing
which molecular cloud a star comes from gives only a vague idea of its
age. But researchers have come up with a way to determine the age of
stars by measuring their acoustic vibrations using ultrasound technology
similar to that used in the field of medicine.
“Think of it as ultrasound of stellar embryos,” explains Professor
Jaymie Matthews, a co-author of the study from the University of British
Colombia. “Stars can vibrate due to sound waves bouncing inside. We
detect the sound vibrations across the vacuum of space by the subtle
changes in stellar brightness. Then we translate the frequencies of
those vibrations into models of the structures of those stars’ hidden
First author Konstanze Zwintz, a postdoctoral researcher at KU
Leuven's Institute for Astronomy, and her colleagues studied the
vibrations of 34 stars aged under 10 million years and sized between one
and four times the mass of our 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," says Dr. Zwintz.
While theoretical physicists have posited before that young stars
vibrate differently than older stars, Zwintz' study is the first to
confirm these predications using concrete data from outer space.
"We now have a model that more precisely measures the age of young
stars," says Zwintz. "And we are now also able to subdivide young stars
according to their various life phases."
The researchers studied the nebula known commonly as the
Christmas Tree Cluster. Their data was obtained from the Canadian MOST
satellite and the European CoRoT satellite as well as from ground-based
facilities such as the European Southern Observatory (ESO) in Chile.