Star trajectory numbers published in a new study suggest that up to 16 stars could come close enough to our galaxy to send potentially dangerous cosmic matter, like comets, crashing into Earth. The prospect of unsettled space material smashing into our planet is enough of a fear for agencies like NASA to start ramping up planetary defense systems. The US space agency has already dedicated a division to track near-Earth objects and there is a plan to carry out an asteroid redirection tests with the European Space Agency (ESA) in the next five years. Astronomer Coryn Bailer-Jones of the Max Planck Institute for Astronomy has now crunched the numbers on the possibility of stellar encounters with the solar system - and a collision is possible. Following a study of the radial velocities of about 320,000 documented stars, Bailer-Jones has surmised that 16 stars could come within two parsecs - or 61 trillion kilometers - of the sun. While a direct hit by a star on the sun or Earth is unlikely