So when nine-year-old Daniel Smith read in a Telegraph astronomy guide last month that Neptune, the most distant of the eight planets, was a mere 4.5 million km from our closest star he instantly recognised that something didn't add up.

A little sleuthing around the relative location of the other planets soon confirmed his suspicion and brought about an explanation an unfortunate typo by the Daily Telegraph.

Our guide, one of two astronomy booklets released last month, should in fact have said 4.5 billion miles, rather than million a fact which Daniel picked up but several pairs of grown-up eyes did not.

Daniel, who lives in New Zealand with his family, explained his reasoning in a letter to his grandfather Don Smith, a Telegraph reader from Felixstowe, Suffolk, who had sent him the books as a present.

He wrote: "Dear grandad, I really liked the solar system books you got us. They were very interesting! But I noticed a mistake.

"It said Neptune was 4.5 million km when mercury was 57.9 million km. I found the problem by looking at the other planets. It turns out that Neptune was supposed to say 4.5 billion km from the Sun."

He signed off the letter "Love, Daniel," adding: "PS, give grandma a kiss from me!"

Mr Smith forwarded the note on to the Telegraph noting how impressed he was that a child had digested the "quite intelligent" booklets so thoroughly that he picked up on the miscalculation.

We quite agree, and would like to thank Daniel for reading our booklets so thoroughly.

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Astronomy mistake picked up by nine-year-old