Astronomer Sir Patrick Moore, host of The Sky at Night, is to be fitted with a pace-maker after suffering heart problems, his agent said.
Stargazer Sir Patrick Moore is a self-taught musician and composer
The 83-year-old was admitted to St Richard's Hospital in Chichester, West Sussex, on Tuesday.
His agent, Robert Voice, said Sir Patrick would have a pacemaker fitted on Thursday in a routine operation.
"There's nothing to be concerned about; it wasn't an emergency," said Mr Voice, adding Sir Patrick was in "good form".
He is expected to be released from hospital in a few days' time.
Sir Patrick, who was knighted in 2001, has presented The Sky at Night, the UK's longest-running TV show, since it began on the BBC in 1957.
He also won a Bafta for his services to television in 2001 and became a fellow of the Royal Society.
Sir Patrick is listed in the Guinness Book of Records as the longest-serving TV presenter.
He has taken part in TV coverage of events such as the first pictures of the far side of the Moon in 1959, the Apollo Moon landings of 1969 and the UK's total solar eclipse in 1999.
Away from the TV screen, he is a well-respected astronomer and was involved in the lunar mapping before the Nasa Apollo missions.
He met many of the 20th Century's most famous scientists, such as rocket pioneer Wernher von Braun, who masterminded the V2 missiles and the post-war American space programme.
Sir Patrick recently recalled that among his favourite memories was playing piano in accompaniment to Albert Einstein on violin.
He was a well-known author of astronomy books when he was chosen as presenter of The Sky at Night.
Sir Patrick has written more than 60 books on astronomy
He became fascinated by astronomy from the age of six, when he picked up a book on the subject belonging to his mother.
By the age of 11, Sir Patrick was elected to the British Astronomical Association. 50 years later, he became its president.
In 2004, Sir Patrick missed presenting The Sky At Night for the first time in 47 years after being struck by food poisoning.
His other TV credits include the role of Gamesmaster in the 1990s computer games show of the same name.