Astronomers were shocked by new research on white dwarves. It seems they aren’t just inactive balls of superdense matter but a major part of them is burning hydrogen on their surface prolonging their lifespan even further.
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We usually imagine white dwarves as dead cores of burned-up stars that are essentially doing nothing and cooling down. But new observations from the Hubble Telescope are turning this idea on its head. An international team of astronomers found the first evidence that white dwarves are burning up hydrogen on their surfaces and thus further prolonging their already incredibly long aging.
As Jianxing Chen – research lead from the Alma Mater Studiorum Universita di Bologna and the Istituto Nazionale di Astrofisica – says: it was shocking. Evidence of stable thermonuclear activity on the surface of white dwarves was expected by almost nobody. You need to remember, white dwarves, are very common in the Universe. Experts estimate that about 98 % of stars will end as white dwarves including our own Sun. Yet, we don’t fully understand their evolution nor the processes that take place on their surfaces.
Chen’s team studied the evolution of white dwarves by observing two spherical stellar clusters – M3 and M13. These clusters share a number of properties including their age or metallicity. At the same time, they differ in the parameters of stars from which white dwarves are created. Mostly we are talking about stars of the so-called Horizontal branch of the Hertzsprung-Russel diagram where you can find stars with a mass close to the Sun that are going through the change into red giants. In the M13 cluster, these stars are hotter.
The researchers observed both clusters using the Hubble telescope in the ultraviolet part of the spectrum. That allowed them to compare more than 700 white dwarves from both of the clusters. Comparisons and computer simulations show that about 70 % of the white dwarves in the M13 cluster burn hydrogen on their surface. This prolongs their already astronomically long aging processes. The hydrogen comes from a thin layer that surrounds the surface of the white dwarves.
This may seem like a cute detail from the life of white dwarves. But this Discovery could have long-lasting repercussions. This is because astronomers were so convinced in the process of white dwarves cooling down that they used it as an astronomical clock to measure a cluster’s age. But this discovery makes it almost certain that these measurements are wrong.
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