Flashy Neighbor 
Today, the Sun races around the galaxy with only its planets in tow. But when the solar system was forming, it was a different story. The Sun had lots of company then — it was a member of a cluster of more than a thousand stars. And one of those stars exploded quite close to the newborn Sun.
Evidence for this “flashy” neighbor comes from meteorites — space rocks that have fallen to Earth. Most meteorites formed when the solar system itself did, so they’re time capsules that preserve the conditions that prevailed just before Earth was born.
By analyzing meteorites, astronomers have concluded that a massive star likely exploded less than one light-year from the young Sun. That’s only a quarter of the distance to what’s now the closest star system, Alpha Centauri.
When a massive star explodes, it hurls radioactive debris into space. Some of the radioactive elements from the neighboring supernova splattered the solar system and became embedded in chunks of rock. Over time, these elements decayed into other elements, altering the chemistry of compounds in the rocks.
An explosion so close to home may have changed the structure of the solar system, making it easier to produce a planet like Earth. And it tells us that the Sun was born in a large cluster, because the heavy stars that explode as supernovae form only in such clusters. So a flashy neighbor helped mold our current neighborhood — and provided long-lasting clues to how it happened.
Script by Ken Croswell, Copyright 2012