The Andromeda Galaxy, our nearest galactic neighbor. Wikimedia Commons/Adam Evans Update: Unfortunately, it appears that this was not a full-blown gamma ray burst, but instead just a run of the mill X-ray source in our nearest galactic neighbor, as reported by University of Leicester astrophysicst Phil Evans, one of the scientists working on the Swift project.

The NASA Swift gamma ray burst mission just spotted an incredibly rare example of the most violent explosion in the universe in our cosmic backyard.

Astrophysicists on Twitter got excited when the probe designed to detect the extremely bright pulses of cosmic energy called gamma ray bursts saw a signal in the Andromeda galaxy, our home galaxy's nearest large galactic neighbor.

Here's Robert Rutledge, an astrophysicist studying neutron stars at McGill University in Montreal:

Hmm... a gamma ray burst (image trigger - so low significance) just came at us from M31 -- The Andromeda Galaxy. About 5 minutes ago.... — Robert Rutledge (@rerutled) May 27, 2014

Gamma ray bursts are among the most powerful and mysterious events in our universe. The bursts consist of short pulses of intense radiation that can travel billions of light years and still be observable from Earth.

If a gamma ray burst were to happen in our galaxy, and be pointed directly at us, it would probably wipe out our ozone layer and cause a mass extinction. Fortunately, all the bursts we've seen, including this one, are far enough away that they are harmless to life on Earth.

Gamma ray bursts were first noticed by Cold War satellites designed to detect Soviet nuclear tests. The bursts that we have observed happened in galaxies billions of light years away. The majority of gamma ray bursts last for a few seconds and appear to be the result of the collapse of enormously massive stars dozens of times the size of our sun.

Some gamma ray bursts shine for only a fraction of a second and have more mysterious origins. One theory is that the short gamma ray bursts are caused by the collision of two neutron stars: the incredibly dense and magnetically powerful remnants of supernovas. Scientists on twitter are hypothesizing that this new one could have been one of those rare collisions. If it was here's how that would look:





Gamma ray bursts are generally seen in galaxies that are billions of light years away. What makes this burst exciting is that it's happening in the Andromeda Galaxy, only about two and a half million light years away. This could be one of the closest ever recorded.

The actual event causing the burst happened about two and a half million years ago, but the light and radiation from that burst just flew past our home planet in the last few hours.

The burst could give astronomers and physicists an enormous amount of data on the origins of these huge explosions. You can follow along with the astronomers' excitement on twitter with the hashtag #GRBM31.

Until they fully analyze the data, we can't know for sure that this is a gamma ray burst. Some have suggested it could be an "Ultraluminous X-ray Source," which would actually be even more fascinating because we don't know what causes them. Caltech astrophysicist Christian D. Ott thinks this might be a soft gamma repeater, or SGR, a weaker type of burst given off by a neutron star with a strong magnetic field:

OK folks, #GRBm31 is exciting, but it for sure wasn't energetic enough to be a GRB from a neutron star collision or stellar collapse. SGR? — Christian D. Ott (@hypercott) May 28, 2014

However this works out, this is an exciting moment in astrophysics.