http://www.newsweek.com/cow-explosion-at2018cow-neil-gehrels-swift-observatory-atlas-data-supernova-1288442

Something highly unusual was picked up by the Asteroid Terrestrial Impact Last Alert System (ATLAS) on June 16, 2018. The discovery of a strange flare in the sky—brightening and fading—was reported in an astronomical telegram, which then alerted scientists. The source was named AT2018cow—based on a naming convention for transient sources where the last three letters are randomly assigned. Understandably, though, scientists quickly nicknamed it “the Cow”.

Astronomers all around the world started watching the Cow, which is one of the strangest and most observed objects recently discovered. Measurements of its brightness and wavelength suggest that it is located close to 200 million light years away, far outside our own galaxy. This means that the explosion would have been extremely bright to have been detected at all, producing as much energy as the sun radiates in 1,700 years.