Does every star have planets?

In 1992, astronomers discovered the first planet outside the solar system. Since then, telescopes have spotted thousands of these so-called exoplanets orbiting not only stars similar to the sun but also in binary star systems; small, cool stars called red dwarfs; and even ultradense neutron stars. It’s enough to make you wonder: Does every star out there have at least one planet orbiting it?

In a word, no, said Jonathan Lunine, chair of the Department of Astronomy at Cornell University. That is, at least not as far as we know.