Stars with a mass similar to our Sun end their lives as white dwarfs. Just before that, they lose part of their mass. how much ? Astronomers provide an answer thanks to a unique study of a white dwarf at the center of a planetary nebula.
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What astronomers call open clusters, there are about a thousand in our Milky Way Galaxy. Each contains several thousand stars that were born at the same time but, depending on their mass, may be in different stages of their lives today. That’s why researchers care so much about it. Because the open clusters form a kind of laboratory that allows her to test her theories about stellar evolution.
Stars evolve according to their mass
One question that remains unanswered is how much mass the star is losing. Especially at the end of his life. Astronomers estimate that stars like our Sun, for example, lose a little less than half their mass when they evolve into white dwarfs. It’s not nothing. Although it is known that more massive stars lose more.
However, a very small white dwarf has never been studied before. These stars develop in the cores of planetary nebulae formed from gas spewed out by the dying star. But until now, these white dwarfs have remained too faint and too distant for astronomers to dissect them.
A look at a white dwarf in the middle of a planetary nebula
But this is what researchers from the University of Tübingen (Germany) were able to do thanks to one of the largest telescopes in the world, the Large Telescope of the Canary Islands, or GranTeCan. In the newspaper Astronomy and astrophysicsThey tell how they observed and studied the spectrum of the central star of the planetary nebula in the M37 cluster. A star now weighs 0.85 solar masses and has therefore lost 70% of its mass during its lifetime. Astronomers also noticed that the star no longer had hydrogen on its surface. It is enough to take into account the occurrence of an unusual event in its recent past, such as a short-lived explosion of nuclear fusion.
