An exploding supermassive star

Supermassive black holes—millions to billions times more massive than the Sun—reside at the center of almost every galaxy, and they power distant, bright quasars that already existed when the universe was only a billion years old. But understanding how such supermassive black holes could form so early in the universe is a challenge. Some theoretical models suggest that they could have originated as supermassive stars, comprising 10 000 or more solar masses, that collapse into black holes and then grow through subsequent accretion and galaxy mergers to reach the observed sizes. (For more on the earliest stars, see the article by Tom Abel, Physics Today, April 2011, page 51 .)

New supercomputing simulations by Ke-Jung Chen (University of California, Santa Cruz) and colleagues have revealed that primordial stars of around 55 000 solar masses might not all end up as black holes, as models predict—they can instead die as extremely energetic supernovae. As such a massive star burns helium in its core, general relativistic effects can make it dynamically unstable, triggering a rapid collapse of the star’s core and igniting explosive thermonuclear burning. The star erupts so violently and completely that no massive remnant at all is left behind.

This two-dimensional visualization shows a mirrored half-slice through the interior of a simulated supermassive star of 55 500 solar masses a day after the onset of the explosion. The outer circumference is slightly larger than Earth’s orbit. In the inner helium core, nuclear burning is converting helium to oxygen and powering violent fluid instabilities that further accelerate the reaction. Within a few more hours, the explosion will have released enough energy to completely unbind the star. The result is expected to also prevail in three dimensions. (K.-J. Chen et al., Astrophys. J. 790, 162, 2014, doi:10.1088/0004-637X/790/2/162 ; image submitted by Ke-Jung Chen.)

To submit candidate images for Back Scatter, visit http://contact.physicstoday.org .