Here are Hubble telescope views of the rapidly fading visible-light fireball from the most powerful cosmic explosion recorded to date. For a brief moment the light from the blast was equal to the radiance of 100 million billion stars. The initial explosion began as an intense burst of gamma rays, which happened on Jan. 23, 1999.

The blast had already faded to one four-millionth of its original brightness when Hubble made observations on February 8 and 9 [image on left]. Hubble captured the fading fireball embedded in a galaxy located two-thirds of the way to the horizon of the observable universe. The picture on the right is a close-up view of the galaxy, the finger-like filaments extending above the bright white blob of the gamma-ray fireball.