Astronomical detective work led to the stunning discovery of a large new world beyond Pluto – and hiding in plain sight. The object could be the biggest in the Kuiper belt of rocky objects that orbit the outer reaches of the solar system.

The first data made public about the object suggested the object could be up to twice the size of Pluto, but newly revealed observations indicate the object is about 70% Pluto's diameter.

The find suggests more such objects are waiting to be discovered and is likely to reignite the fierce debate about what constitutes a planet.

On Thursday, an email with the subject, "Big TNO discovery, urgent" was sent to a popular astronomy mailing list. The message described the discovery of a "very bright" object that was creeping along slowly beyond the orbit of Neptune - making it a Trans-Neptunian Object, or TNO.

If the reflectivity is as dim as most other distant, rocky objects that have been studied, the object "would be larger than Pluto," Jose-Luis Ortiz, an astronomer at the Sierra Nevada Observatory in Spain, wrote in the email. Pluto is about 2300 kilometres across.

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The reason the second one in particular may not be called a planet is the same reason that some poeple think Pluto should not be called one -- it is an overgrown Kuiper belt rocky objects. The Kuiper belt, where Pluto (not Jupiter as I said) is found apparently has many solid objects of ice and rock in it.

Anyway, we're up to at least ten if the debate doesn't squash the motion.

A