Research Highlights

• Subject Category:
  • Space & astronomy

Published online: 29 April 2009 | doi:10.1038/nchina.2009.90

Cosmology: Helium helps

Tim Reid

Introduction

© (2009) ESO

Type Ia supernovae are among the most consistently bright explosions in the universe, making them important tools for astronomers to judge distances in space. Even so, mysteries remain about how they are formed. Now, Bo Wang at Chinese Academy of Sciences in Yunnan and co-workers¹ have discovered why some stars explode into supernovae at much younger ages than others.

A type Ia supernova occurs when an ageing star enters a final, very dense state called a white dwarf, and accretes mass from a neighbouring 'donor' star. When the white dwarf grows above a critical mass, it collapses in on itself, leading to a huge thermonuclear explosion.

Until now, models could not explain the observation that many stars explode into supernovae when they are less than 100 million years old. Wang and co-workers used calculations of stellar evolution to show that these youngest supernovae could occur if the donor star is a helium star, which emits considerably more helium than hydrogen.

The study suggests that white dwarf/helium star binary systems could account for a large proportion of observed young supernovae. They could even be sources of detectable gravitational waves — fluctuations in the curvature of space-time which are predicted by general relativity, but have never yet been directly observed.

The authors of this work are from:
National Astronomical Observatories and Yunnan Observatory, Chinese Academy of Sciences, Kunming, China; Graduate University of Chinese Academy of Sciences, Beijing, China; Department of Physics and Chemistry, Henan Polytechnic University, Jiaozuo, China.

Reference

1. Wang, B., Meng, X., Chen, X. & Han, Z. The helium star donor channel for the progenitors of type Ia supernovae. Mon. Not. R. Astron. Soc. doi:10.1111/j.1365-2966.2009.14545.x (2009). | Article |