White dwarfs are small, very dense stars that are typically the size of a planet. They are what stars like the Sun become after they have exhausted their nuclear fuel. Watch new episodes of #HowtheUniverseWorks Wednesdays at 9p on Science Channel and #discoveryplus. You can also stream next week’s episode, exclusively on discovery . Download and subscribe here: http://discoverypl.us/388k3GH | Science Channel