…Show them this:
Astronomers discover binary stars in ‘impossibly’ tight orbits
by George Dvorsky
A team of scientists using the United Kingdom Infrared Telescope (UKIRT) in Hawaii have found four different pairs of binary systems whose stars are so close to each other that it takes them less than four hours to orbit one another. Previous estimates indicated that stars shouldn’t be allowed to do this — they should consume each other, creating one giant mass.
This observation forces astronomers to throw away previously held notions of what binary star systems might look like.