PARIS: Astronomers using the most advanced land telescope in the world said on Wednesday they had unlocked knowledge about how formidable "gas giant" planets such Jupiter and Saturn come into being.

These vast but uninhabitable worlds are created by gobbling up gas and dust that envelope young stars in a murky disc, they believe.

The evidence comes from observations of a youthful star called HD 142527 which is located more than 450 light years from Earth.

Stars are born from a cloud of cosmic gas and dust, which surrounds the star for millions of years after it bursts into light.

Around HD 142527, the astronomers found an intriguing gap in the dusty disc, and they believe this was carved out by newly-forming gas giants.

The planets absorb the debris into their expanding mass as they circle the star, according to the investigation, appearing in the journal Nature.

The planets also feast on gas that streams across the gap from the outer zone of the disc to the inner zone, which helps to feed the infant star.

"Astronomers have been predicting that these streams must exist, but this is the first time we've been able to see them directly," said University of Chile astronomer Simon Casassus.

Casassus' team used the Atacama Large Millimetre/Submillimetre Array, or ALMA, a hi-tech telescope still under construction at the European Southern Observatory's site in Chile's Atacama Desert.

By observing light at submillimetre wavelengths, ALMA is impervious to glare in the infrared or visible-light part of the spectrum.

Using it, the team spotted two dense streams of gas flowing across the gap, as well as residues of gas within the gap itself.

"We think that there is a giant planet hidden within (the gap), and causing each of these streams," said Casassus' colleague, Sebastian Perez.

"The planets grow by capturing some of the gas from the outer disc, but they are really messy eaters. The rest of it overshoots and feeds into the inner disc around the star."

The gap itself is huge. It starts at about 10 astronomical units (AUs) from the star -- meaning, 10 times the distance of our Earth from the Sun -- and ends at more than 140 AUs. The putative planets probably lie at around 90 AUs from the star.

In a separate paper, also published by Nature, astronomers using a radio telescope in Parkes, Australia said that an outpouring of gas and charged particles from the centre of the Milky Way is a byproduct of the birth of new stars.

The mysterious energy was first detected in 2010, but only now has it been mapped.

The outflow contains about a million times the energy of an exploding star, and extends 50,000 light years -- about half the diameter of our galaxy -- and may play a role in generating the Milky Way's magnetic field.

The energy blast would be lethal for life on Earth, but there is no danger as the jets are moving in a completely different direction to our home.