The Swift robotic spacecraft was launched
into orbit on November 20, 2004 to observe
gamma-ray bursts (GRBs).
GRBs are flashes of gamma rays associated
with extremely energetic explosions, usually
from dying stars and they are the brightest
electromagnetic events known to occur in the
universe.
One of the GRBs depicted in this clip hit the
Earth directly but it was too distant to have a
noticeable effect. However, scientists theorize
that in the future, a GRB could devastate
life on Earth, which they believe has happened
in the past.
It has been hypothesized that a close-range
gamma-ray burst from within the Milky Way,
pointing directly towards the Earth, could cause
a mass extinction event on our planet.
Video (about 1 min):