When will a star explode?
Dr. Eran Ofek
Dr. Eran Ofek of the Department of Particle Physics and Astrophysics and his colleagues have identified an early-warning system for the violent starbursts called supernovae.
Supernovae are intensely bright stellar explosions that result in the emission of elements into the universe—elements which comprise our bodies and the world around us. Knowing when they will occur is important in better understanding the functioning of the solar system.
What he and his colleagues have found is that, often, before those explosions occur, certain large stars undergo a sort of “mini-explosion,” throwing a good-sized chunk of their material off into space. Though several models predict this behavior and evidence from supernovae points in this direction, actual observations of such pre-explosion outbursts have been rare. These mini-outbursts occur just 40 days, approximately, before supernovae explosions. Never before have scientists tracked down this mini-explosion to mere weeks before a star dies.
The findings, which recently appeared in Nature, help to clarify the series of events leading up to the supernovae, as well as provide insight into the processes taking place in the cores of such massive stars as they progress toward the final stage of their lives.
Dr. Ofek conducted this research as a participant in the Palomar Transient Factory (PTF) project (led by Prof. Shri Kulkarni of the California Institute of Technology), which searches the skies for supernova events using telescopes at the Palomar Observatory in California. He and a research team from Israel, the UK, and the US decided to investigate whether outbursts could be connected to later supernovae by combing for evidence of them in observations that predated supernova sightings by the PTF. The fact that they found such an outburst occurring just a little over a month before the onset of the supernova explosion came as a surprise to them, says Dr. Ofek. But the timing and mass of the ejected material helped them to validate a particular model that predicts this type of pre-explosion event.
The violence and mass of the pre-explosion outburst they found, says Dr. Ofek, point to its source in the star’s core. The material is speedily ejected from the core straight through the star’s surface by the excitation of gravity waves. The researchers believe that continued research will show such mini-explosions to be the rule for this type of supernova, and their model may be used in the future to predict fairly accurately when a star will explode.
Dr. Ofek is supported by the Willner Family Leadership Institute and Ilan Gluzman, Secaucus, NJ. He is the incumbent of the Arye and Ido Dissentshik Career Development Chair.