'Epic' comet Ison approaching the Sun
27 November 2013 Last updated at 23:41 GMT
Comet Ison's close encounter with the Sun could give astronomers and stargazers a visual treat to be savoured.
Described as the "comet of the century", Ison's loop around the Sun has been eagerly awaited, but scientists fear it could break up during its pass.
Rebecca Morelle reports.