Study: Life, a white dwarf

There probably has never been a person who hasn’t gazed up at the stars in wonder. It must be instinct.

While the idea that Earth and all its creatures are connected to stardust is nothing new, a study published Monday in the journal Nature Astronomy suggests that white dwarf stars, specifically, are the primary source of carbon atoms in the entire Milky Way.

Carbon, if you remember from high school chemistry, is the building block of life.

A star dies about once every second. Some explode and turn supernova, becoming a black hole or perhaps a neutron star. But most deteriorating stars become white dwarfs, and white dwarfs are mostly what you see when you look up at night. They’re very dense with a mass comparable to the sun (a yellow dwarf star) and volume comparable to Earth.

An international team of scientists analyzed open star clusters (groups of a few thousand stars) from a Hawaii observatory, finding white dwarfs contribute more to life in the cosmos than previously believed.

White dwarfs are hot, dense stellar remains with temperatures reaching 100,000 Kelvin. After billions of years they cool and eventually dim, but right before they collapse, their remnants travel through space. Those remnants contain elements such as carbon — the fourth most abundant chemical in our universe, and the building block of most living cells.

Scientists already knew the carbon in our galaxy originated from stars, through the fusion of three helium nuclei. Until now they weren’t sure which type of star spread the most carbon. Some scientists favored supernovae, others, white dwarfs.

This study found that the white dwarf stars’ masses were larger than anticipated, relative to their initial mass when the stars first formed.

“Our study interprets this kink in the initial-final mass relationship as the signature of the synthesis of carbon made by low-mass stars in the Milky Way,” Paola Marigo, a researcher at the University of Padua in Italy, and lead author of the study, said in a statement.

That suggests the carbon was essentially trapped in this raw material that formed our sun and solar system more than four billion years ago.

Carbon makes up all organic matter on Earth, including the human body, with large amounts stored in the ocean. The carbon cycle moves this life-sustaining element from the atmosphere and oceans into organisms, and back again.

The study can be accessed at Go.nature.com/2Z67Spk.

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Sholeh Patrick is a columnist for the Hagadone News Network who wasn’t smart enough to become an astrophysicist. Contact her at Sholeh@cdapress.com.