What do exploding stars and presidential politics have in common? The two come together in the person of Donald Lamb, a University of Chicago astrophysicist and director of the Flash Center , where researchers study thermonuclear detonations in space.
Lamb also lives in Hyde Park, the Chicago neighborhood that has become world famous thanks to another long time resident, Barack Obama. Lamb became an early supporter of the current president going back to Obama’s state senator days. He joined the presidential campaign in 2007 and soon became identified as one of the prominent scientists who helped sell Obama to the reserach community. After the election he was part of the transition team that helped shape the new administration’s science and technology agenda.
In the latest episode of The Universe in Mind podcast, Lamb speaks in detail about his experiences on the campaign trail and about Obama’s attitudes toward science. He also speaks about his own area of expertise: Type Ia supernovae, and shares some recent insights into how these cosmic H-bombs work.
Type Ia supernovae have become increasingly important because they are the brilliant standard candles that allow astronomers to measure the distances to galaxies halfway across the universe. A decade ago such measurements led to the discovery of dark energy, the enigmatic phenomenon that is causing the expansion of the universe to accelerate.
Lamb and his colleagues are concerned with exactly how these explosions unfold. It’s a science of extremes, involving events of unimaginably high energy playing out over fractions of a second.
One of the most surprising discoveries to come out of this work is that type Ia supernovae can be thought of as exploding from the outside in. This kind of supernova always occurs in a close binary system, where gas from one star can spill over onto a white dwarf companion. A white dwarf is already about one million times the density of the Sun. The additional material further increases the pressure and temperature in the white dwarf’s interior until spontaneous bubbles of nuclear burning begin to form.
Lamb was part of a team that did the first full 3-D model of a white dwarf exploding under theses circumstances. What they found was that the tiny flame that starts somewhere inside the white dwarf rises very quickly, like a hot air balloon. In an instant it is already at the surface of the star. There, gravity confines it like an invisible lid, so the burning front then races across the surface of the white dwarf and meets itself on the far side. The shock that results is what turns the burning into an all-consuming detonation. You can watch a video that shows this scenario in action, and it’s quite a spectacle.
It’s a big change from how these dramatic explosions were once envisioned. And according to Donald Lamb, it’s change we can believe in.
Ivan Semeniuk is host of The Universe in Mind podcast and a science journalist in residence at the Dunlap Institute for Astronomy and Astrophysics, University of Toronto.