The operators of the Hubble Space Telescope say the orbiting observatory has snapped photos of an approaching comet.

The Baltimore-based Space Telescope Science Institute says the Comet Ison is being called the "comet of the century" because it could be brighter than the full moon when it makes its closest pass by the sun in late November.

The institute says the pictures taken earlier this month show the comet slightly inside Jupiter's orbit, about 620 million kilometers from the sun. The institute serves as the science operations centre for the Hubble.

Hubble scientists say preliminary measurements show the nucleus of the comet is about three to four miles across. The comet was discovered in September by a Russian team.