An embryonic planet still in the first stages of formation has been discovered enclosed in a “womb of gas” around a young star, British astronomers will announce today.

The protoplanet, known as HL Tau b after its parent star, HL Tau, could be just a few hundred years old, which would make it the youngest to have been observed. It is likely to grow into a gas giant, similar to Jupiter and Saturn, and it will offer fresh insights into the way that planets form discs of dust and gas around stars.

Jane Greaves, of the University of St Andrews, who led the Anglo-American team that found it, said: “The planet will probably take millions of years to settle down into its final form of something like Jupiter. We really are seeing it very early – even a bit like the first cells that make up a human embryo in the womb.”

The discovery, to be presented today at the Royal Astronomical Society annual conference in Belfast, was made while the research team was studying HL Tau, a star about 520 light years from Earth in the constellation of Taurus.

Observations with telescopes at the Very Large Array in New Mexico, US, indicated that dust in a disc around HL Tau was starting to condense into a planet. This was confirmed by observations at Jodrell Bank in Cheshire, which is threatened with closure because of a funding shortfall.

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