An alternate possibility is a relatively recent burst of star formation in the inner galaxy, probably within the last 10 million years. (scientificamerican.com)
The team that observed this most recent burst said it believes the burst came from a point 5.5 billion light - years away though it has no idea what caused it. (ibtimes.com)
In most instances, they detected radiation levels up to a million times fainter than those produced during recent bursts. (discovermagazine.com)