What is a white dwarf?

A white dwarf is the remnant core of a star.  A star is layered like an onion, with the lighter elements on the outside and heavier elements inside.  After nuclear fusion causes all of the helium to go to carbon, it stops this process and instead compresses, becoming very dense.  Since the star is not burning (converting) any more fuel, over time it will cool and the light will fade, turning it into a black dwarf.

White dwarfs started out as small stars (like our Sun to about 5 times the mass of our Sun), and are not large enough to go supernova and form a neutron star.  



All Answers

Answers by Expert:

Ask Experts


Brad Tucker


I'm happy to answer any general questions about Astronomy, Astrophysics, and Cosmology. I'm also happy to take general, specific, and detailed questions related to supernovae, Baryonic Acoustic Oscillations, the Cosmic Microwave Background, dark matter, dark energy, and the Big Bang Theory. I'm also happy to chat about Astronomy/Astrophysics education and careers, and philosophy and science.


I am a professional research astronomer/astrophysicist/cosmologist. My research focuses on studying supernovae and using them to measure the properties of the Universe, such as how fast it is growing and what it is made of. I also frequently give talks to school groups and the public, and am a regular guest on various radio stations.

Current Research Fellow at Mt. Stromlo Observatory, the Australian National University, and in the Department of Astronomy, University of California, Berkeley.

Lots of journals, including the Astrophysical Journal, the Astronomical Journal, and Nature. I am currently in the middle of writing my first popular book.

B.A. Philosophy, University of Notre Dame, Notre Dame, IN USA B.A. Theology, University of Notre Dame, Notre Dame, IN USA B.Sc. Physics, University of Notre Dame, Notre Dame, IN USA Ph.D. Astrophysics, Mt. Stromlo Observatory, the Australian National University, Canberra, ACT, Australia

©2016 All rights reserved.