'So many questions' about Comet Ison
Astronomers say some part of Comet Ison may have survived its close encounter with the Sun.
It was thought the giant ball of ice and dust had been destroyed by the Sun's heat and gravitational pull.
But US naval astrophysists say something re-emerged two hours after the comet disappeared from view.
Karl Battams is an astrophysicist at the US Naval Research Laboratory in Washington DC and has been watching for the comet from the solar telescope control room at Kitt Peak Observatory in Arizona.
- BBC News