Scientist discovers how stars form, evolve, and die

Finding a new chemical reaction in space could help explain stars

University of North Dakota scientist Mark Hoffmann's version of Star Search goes a long way—a very long way—out into the universe.

Hoffmann, a computational chemist, and his colleagues Tryve Helgaker, a well-known Norwegian scientist, and co-authors E.I. Tellgren and K. Lange, also working in Norway, have discovered a molecular-level interaction that science had puzzled over for decades but had never seen.

That discovery, it turns out, may redefine how science views chemical compound formation. It also answers questions about what goes on in places like white dwarfs, the super dense cores of stars closing in on the end of their life cycle.

"We discovered a new type of chemical bonding," said Hoffmann, known globally for his pioneering work in the theory and computer modeling of chemical compound formation. "That's a pretty bold statement, but I'm not kidding you! It's a brand new type of chemical bonding, not previously known to science."

Hoffmann and his colleagues have rewritten the chemical rule book for assessing what happens in the night sky. It's about answering timeless questions such as how do stars form, evolve and eventually die.

Their work also provides the secret how some compounds form in the distant universe.

This momentous discovery appears in an article in the current issue of the internationally respected journal Science .

"Our discovery addresses one of the mysteries in astrophysics about the spectrum of white dwarf stars," Hoffmann said. "White dwarfs have an unusual spectrum that has been thought to result from polymerized hydrogen and helium which of course do not occur on Earth.

"It's possible out there because the magnetic fields on white dwarfs are several orders of magnitude larger than anything that can be generated on Earth."

The closest white dwarf, Sirius B, is a faint twin to the brightest star in the night sky, Sirius A. It's about the same size as our sun, but much denser; its average density is 1.7 metric tons per cubic centimeter, or about 3,000 pounds compressed into a box the size of a sugar cube.

Hoffmann and his team described a magnetically-induced bonding process between materials.

"There was speculation that this phenomenon should exist, but no one had the proof, no one—until the team I'm on described the process—had the theoretical structure and the computational tools to address this," he said.

On Earth, even the boldest military experiments generate a peak of maybe 1000 Tesla—a measure of magnetic force (fridge magnets generate a thousandth of one Tesla). But on Sirius B, for example, magnetic fields are on the order of 200,000 to 400,000 Tesla, enough to challenge the electronic interactions that dominate the chemistry and material science to which we know on Earth.

Such vast magnetic fields directly alter the way atoms come together—and can alter the chemical reality we know on Earth.

"What we had before we discovered this was basically a paper-and-pencil model of what goes on in the universe. Compared to what's out there in places such as white dwarf stars, the magnetic fields we can generate here—even with the strongest magnets—are pathetic."

So how did they do it?

"We computationally modeled the behavior that we theorized, based on universally applicable physical principles," Hoffmann said.

The team's computer model proved their theory. Now it's up to astrophysicists to test the model by old-fashioned observation of the stars.