This is an image from the computer simulation of HL Tau and its surrounding disc. In the model the dense clump (seen here at top right) forms with a mass of about 8 times that of Jupiter at a distance from the star about 75 times that from the Earth to the Sun. Image: Greaves, Richards, Rice & Muxlow 2008).

The youngest planet ever to be seen has been captured in its earliest stage of formation in a disc of gas and rocky debris around a star 520 light years away.

Using the MERLIN and Very Large Array radio observatories in the UK and US respectively, a team of astronomers lead by Dr Jane Greaves of the University of St Andrews studied the disc of gas and rocky particles surrounding the extremely young star HL Tau and identified a 'clump' of material at a distance of about 65 AU from the parent star, twice as far from HL Tau as Neptune is from our Sun.

VIDEO Dr Jane Greaves of the University of St Andrews speaks with Astronomy Now Web Editor Emily Baldwin about her discovery of the youngest forming planet yet seen.   PLAY

"This star is probably less than 100,000 years old," says Greaves, "and we see a distinct ball of gas and dust orbiting around it, which is exactly how a protoplanet should look." The protoplanet is made up of dust grains and fist-sized rocks, and could form a planet about 14 times as massive as Jupiter.

Using computer simulations, team member Dr Ken Rice of the University of Edinburgh showed that a massive protoplanet of around 8 Jupiter masses could condense out of a disc into a self-constrained structure at a distance comparable to that observed by the radio telescopes. "The simulations show that the gravitational instability model really does work," comments Greaves. "This is the first image of a protoplanet that has ever been made and we've also captured the environment in which the planet is forming."

The team hope to use the eMERLIN telescope array to make similar observations of other protoplanetary discs, which may be able to resolve Earth-sized exoplanets.