It turns out, Green and his team came across the remnants, now called G1.9+0.3, more than 20 years ago using the Very Large Array (VLA) radio telescope in Socorro, NM, and estimated the object’s age to be 400-1,000 years old. It is near the center of the Milky Way, some 25,000 light-years from Earth.

By comparing notes, the astronomers learned the images taken more than two decades apart documented the expansion of debris from the star's explosion. The images taken in 2007 were about 16 percent larger than the ones taken in 1985.

"This is a huge difference," said Reynolds. "It means the explosion debris is expanding very quickly, which in turn means the object is much younger than we originally thought."

Reynolds also observed the object with the VLA radio telescope to confirm the supernova remnant's rapid expansion. Unlike visible-light telescopes, radio and X-ray telescopes can penetrate the thick clouds of gas and dust in our galaxy.