21 Jun 2011

 

 

 

The solar system after its demise

 

The ultimate destiny of the Sun is the transformation into a white dwarf in approximately 5 billion years, after which it will cool very, very slowly to become almost invisible. The fate of the planets is less certain, but the inner rocky planets will almost certainly be engulfed during the preceding red giant phase, and may be destroyed.
To learn more about this terminal phase that awaits our solar system, Nathan Dickinson, Ph.D. student at the Department of Physics and Astronomy at the University of Leicester (UK), has made spectroscopic observations of as many white dwarfs as possible in search of heavy elements. Some of these heavy elements may be material captured from planetary orbits.
In older, and therefore cooler, white dwarfs, with temperatures below 25,000K, the heavy elements such as oxygen, nitrogen, silicon and iron, sometimes detected, are thought to be from planets. In younger, hotter white dwarfs, some of the elements heavier than hydrogen and helium (the main components of a white dwarf) are intrinsic to the collapsed star. However, the actual amount of heavy elements detected often exceeds that expected theoretically, suggesting an external source.
Understanding the origin of the additional heavy elements in the white dwarf's composition, especially the younger ones, will provide us with a picture of what will happen not only in our own solar system when the Sun enters its red giant phase, but also the fate that awaits most of the stars and planetary systems that populate the Milky Way and other galaxies.

 

by Michele Ferrara & Marcel Clemens

credit: University of Leicester