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Last Updated: Thursday, 27 May, 2004, 21:26 GMT 22:26 UK
Telescope spies 'youngest' planet
Artist's impression of a young planet, Nasa/JPL-Caltech/R. Hurt (SSC-Caltech)
An impression of what it might be like in the CoKu Tau 4 system
Nasa's Spitzer telescope has found evidence around a distant star for a planet that may be less than one million years old.

The infrared space observatory studied five stars in the constellation Taurus, about 420 light-years away.

All had dusty discs around them in which new planets are presumed to be forming out of accreting material.

And for the star CoKu Tau 4, Spitzer saw a clearing in the disc which could have been swept clean by a new world.

Life's necessity

Nasa is excited by the latest findings from its $2bn space telescope launched last August.

It cannot see objects the size of planets directly, but its infrared detectors can penetrate the dusty clouds around very young stars probing the regions in which planets are forming.

Click here to find out more about Nasa's new infrared telescope

Spitzer has now detected significant amounts of icy organic materials sprinkled throughout these "planetary construction zones".

These materials - icy dust particles coated with water, methanol and carbon dioxide - may help explain the origin of icy bodies like comets, the US space agency says.

Scientists believe such comets may have deposited on the primitive Earth water and many other chemicals that became the building blocks of life.

"These early results show Spitzer will dramatically expand our understanding of how stars and planets form," said Dr Michael Werner, Spitzer project scientist at Nasa's Jet Propulsion Laboratory in California.

Earth comparison

The Spitzer finding of a clear path in the CoKu Tau 4 disc - like a vacuum leaving a cleared trail on a dirty carpet, as Nasa described it - is intriguing.

Spitzer is able to reveal more about the structure of such gaps in stellar discs than has been previously possible.

Infographic   BBC
Because CoKu Tau 4 is thought to be only about one million years old, the possible planet would be even younger. Compare this with the Earth which is thought to be more than 4.5 billion years old.

The CoKu Tau 4 planet must therefore be in the earliest stages of its formation and this will help astronomers understand the formation of planets such as our own.

Common process

Spitzer has also discovered two of the faintest and farthest planet-forming discs yet observed.

They surround two of more than 300 newborn stars seen in a dusty stellar nursery called RCW 49, which is about 13,700 light-years distant.

Astronomers believe that the formation of dusty discs around stars is a common phenomenon indicating that planets - which form from the disc - are widespread in the cosmos.

"By seeing what's behind the dust. Spitzer has shown us star and planet formation is a very active process in our galaxy," says Dr Ed Churchwell of the University of Wisconsin, US.

The BBC's Alison Whisson
"A toddler in planetary terms"

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