• The young star, known as HD 163296, is located 330 light-years from Earth 
  • Teams of astronomers confirmed hallmarks of planets orbiting the infant star
  • Rings mark spaces where planets are thought to have formed from dust
  • The finding gives an exciting new insight into the birth of planets 

A trio of 'baby planets' have been found orbiting a newborn star in a discovery that is 'at the frontier of science'.

Astronomers found the planets by looking at patterns of gas around the star.    

Known as HD 163296, the star is located 330 light-years from Earth in the direction of the constellation Sagittarius.

The technique astronomers used to study these worlds could be used to find other newborn planets.

Researchers say they can also use it to see how clouds of gas and dust can form solar systems like our own. 

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Astronomers have discovered a trio of infant plants around a newborn star which is just four million years old. Pictured is an artist's impression of protoplanets forming around a young star

Astronomers have discovered a trio of infant plants around a newborn star which is just four million years old. Pictured is an artist's impression of protoplanets forming around a young star

In the past several years the Atacama Large Millimetre Array (ALMA) in Chile has transformed our understanding of the gas and dust-filled planets that encircle young stars.

An international team of researchers analysed data from various ALMA observations of the young star HD 163296. 

Although researchers have not seen the planets surrounding the new star, they have found telltale signs they exist.

They did this by looking at the proplanetary disk - a rotating mass of dense gas and dust that surrounds a newly-formed star. 

'We looked at the localised, small-scale motion of gas in a star's protoplanetary disk', said Richard Teague, an astronomer at the University of Michigan and principal author on one of the papers.

'This entirely new approach could uncover some of the youngest planets in our galaxy, all thanks to the high-resolution images coming from ALMA,' said Richard Teague, an astronomer at the University of Michigan and principal author on one of the papers.

They looked at the distribution and motion of carbon monoxide (CO) throughout the disk instead of focusing on the dust.

Molecules of CO naturally emit a very distinctive millimetre-wavelength light that ALMA can observe.

Subtle changes in the wavelength of this light provided a glimpse into the kinematics – or motion – of the gas in the disk. 

If there were no planets, gas would move around a star in a very simple, predictable pattern known as Keplerian rotation.

Shifting wavelengths of the CO emission would indicate there was a massive object there.

Pictured is an ALMA image of the protoplanetary disk surrounding the young star HD 163296 as seen in dust. Subtle changes in the wavelength of this light provided a glimpse into the kinematics – or motion – of the gas in the disk

Pictured is an ALMA image of the protoplanetary disk surrounding the young star HD 163296 as seen in dust. Subtle changes in the wavelength of this light provided a glimpse into the kinematics – or motion – of the gas in the disk

WHAT IS ALMA?

Deep in the Chilean desert, the Atacama Large Millimetre Array, or ALMA, is located in one of the driest places on Earth.

At an altitude of 16,400ft, roughly half the cruising height of a jumbo jet and almost four times the height of Ben Nevis, workers had to carry oxygen tanks to complete its construction.

Switched on in March 2013, it is the world's most powerful ground based telescope.

It is also the highest on the planet and, at almost £1 billion ($1.2 billion), one of the most expensive of its kind.

Deep in the Chilean desert, the Atacama Large Millimetre Array, or ALMA, is located in one of the driest places on Earth. Switched on in March 2013, it is the world's most powerful ground based telescope

Deep in the Chilean desert, the Atacama Large Millimetre Array, or ALMA, is located in one of the driest places on Earth. Switched on in March 2013, it is the world's most powerful ground based telescope

'It would take a relatively massive object, like a planet, to create localised disturbances in this otherwise orderly motion,' said Christophe Pinte of Monash University in Australia and lead author on one of the two papers.

'Our new technique applies this principle to help us understand how planetary systems form.'

The team identified two distinctive planet-like patterns in the disk, one at approximately 80 astronomical units (AU) from the star and the other at 140 AU.

An astronomical unit is the average distance from the Earth to the Sun, or about 93 million miles (150m km).

The other team identified the third at about 260 AU from the star. The astronomers calculate that all three planets are similar in mass to Jupiter.

'Though thousands of exoplanets have been discovered in the last few decades, detecting protoplanets is at the frontier of science,' said Dr Pinte.

Pictured is a composite image of the protoplanetary disk surrounding the young star HD 163296. Researchers say they want to find out more about the gas around these planets

Pictured is a composite image of the protoplanetary disk surrounding the young star HD 163296. Researchers say they want to find out more about the gas around these planets

HOW DO PLANETS FORM?

According to our current understanding, a star and its planets form out of a collapsing cloud of dust and gas within a larger cloud called a nebula. 

As gravity pulls material in the collapsing cloud closer together, the centre of the cloud gets more and more compressed and, in turn, gets hotter. 

This dense, hot core becomes the kernel of a new star.

Meanwhile, inherent motions within the collapsing cloud cause it to churn.

As the cloud gets exceedingly compressed, much of the cloud begins rotating in the same direction. 

The rotating cloud eventually flattens into a disk that gets thinner as it spins, kind of like a spinning clump of dough flattening into the shape of a pizza. 

These 'circumstellar' or 'protoplanetary' disks, as astronomers call them, are the birthplaces of planets.

'These studies will also help us to understand how planets like those in our solar system were born,' said coauthor Francois Menard from Grenoble University in France.

Researchers say they want to find out more about the gas around these planets.

'Although dust plays an important role in planet formation and provides invaluable information, gas accounts for 99 percent of a protoplanetary disks' mass,' said coauthor Jaehan Bae of the Carnegie Institute for Science.

'It is therefore crucial to study kinematics of the gas.'

The rings mark spaces where planets are thought to have formed from dust and gas around the star. Pictured here is an artist's impression of the protoplanetary disk surrounding the young star HD 163296

The rings mark spaces where planets are thought to have formed from dust and gas around the star. Pictured here is an artist's impression of the protoplanetary disk surrounding the young star HD 163296

ALMA's high resolution enabled the researchers to measure carbon monoxide's velocity patterns throughout the disk.

'The precision is mind boggling,' said coauthor Til Birnstiel of the University Observatory of Munich.

In a system where gas rotates at about five kilometres per second, ALMA detected velocity changes as small as a few meters per second.

'This allows us to find very small deviations from the expected normal rotation in a disk,' Dr Teague said.

'Planets change the density of the gas near their orbits, which changes the gas's pressure, inducing these corresponding changes in velocity.'

'We are now bringing ALMA front and center into the realm of planet detection,' said coauthor Ted Bergin of the University of Michigan.