Venetia Phair, 87, was 11 when she chose the name Pluto, the Roman god of the underworld, after the planet was discovered by Clyde Tombaugh in 1930.

An instrument aboard Nasa's New Horizons spacecraft heading to Pluto has been named in tribute to her, according to Johns Hopkins University of Baltimore, where the craft was designed and built.

The gadget has been formally called the Venetia Burney Student Dust Counter (VBSDC), or "Venetia" for short.

The role of Venetia is to count and measure dust particle  impacts as the spacecraft travels towards Pluto.

Asteroids

The grains give an indicator of the population of comets, which shed dust as they loop around the Sun, and of asteroids, which lose debris when they collide.

As the dust is too fine to be detected with telescopes, the Johns Hopkins team has placed a screen about the size of a shoebox lid outside the spacecraft.

When dust hits this detector, data is sent to an electronics box on the inside the craft which then calculates the dust's speed and mass.

New Horizons was launched from Cape Canaveral on January 19. It is due to arrive at Pluto in July 2015.

Classical mythology

Phair, nee Burney, was a schoolgirl with an interest in classical mythology when Pluto was discovered.

Her grandfather, a retired librarian at Oxford University, saw a newspaper article about the discovery and read it to the girl, who suggested the name Pluto.

The grandfather was so taken with it that he mentioned it to a friend who was a professor of astronomy at Oxford and who, in turn, campaigned for Pluto to become the official name.

Pluto is the ninth and outermost acknowledged planet of the Solar System, although this status may be scrapped at a meeting in Prague next month of the International Astronomical Union (IAU), which vets claims of new celestial sightings and approves names proposed for them.

Downgraded

Some astronomers say that Pluto is so small and its orbit so unusual that it should be downgraded to the status of a rock, rather than a planet.

And if it is a planet, its role as the farthest from the Sun could be supplanted by another object which was spotted in July last year.

The so-called Planet X has been provisionally named Xena by its discoverers. If the IAU accepts their claim, Xena is likely to be given a classical name.

New Horizons website: http://pluto.jhuapl.edu/news_center/news/062906.html