sciencetech-blog

comments

A recent image from deep space is the first time we've seen planet formation in action, a team of researchers has claimed.

The image shows what appears to be a disk of dust and gas surrounding a star, but debate had raged over whether worlds could actually form in the system.

But now the scientists say they have proof that the circular gaps in the disk are in fact made by forming planets.

University of Toronto scientists say a famous image of a 'disk' 450 light-years away shows planet formation in action. Debate had raged as to whether it was showing planets forming. But now they say it is stable enough to support five separate worlds. Shown is the image of HL Tau

The research was led by Dr Daniel Tamayo from the Centre for Planetary Science at the University of Toronto, Scarborough, and the Canadian Institute for Theoretical Astrophysics. 

The image in question, of the star HL Tau, was taken in October 2014 by the Atacama Large Millimetre/submillimetre Array (Alma) in Chile's Atacama Desert.

The system is 450 light-years from Earth and 22 billion miles (35.8 billion km) across.

By comparison, ours is about 6.6 billion miles (nine billion km) across, when measured to the outermost planet, Neptune.

While those who observed the original image claimed that planets were most likely responsible for carving the gaps, some remained skeptical. 

It had been suggested that the gaps, especially the outer three, could not represent forming planets because they are so close together.

It was argued that planets massive enough to carve such gaps should be scattered violently by the force of gravity and ejected from the system early on in its development.

But Dr Tamayo's study is the first to suggest the gaps are evidence of planetary formation because the gaps are separated by amounts consistent with what's called a special resonant configuration.

In other words, these planets avoid violent collisions with each other by having specific orbital periods where they miss each other, similar to how Pluto has avoided Neptune for billions of years despite the two orbits crossing one another.

The system can be much more stable in a resonant configuration and it's a natural state for planets in the HL Tau system to migrate to, said Dr Tamayo. 

The video below shows where the planets would orbit in the system

The image in question, of the star HL Tau, was taken in October 2014 by the Atacama Large Millimetre/submillimetre Array (Alma), pictured, in Chile's Atacama Desert

HL Tau is a relatively young system, and as it is shrouded in a thick cloud of gas and dust it can't be observed by visible light.

Instead, Alma resolves that issue by using an array of telescopes 9.3 miles (15km) apart, to observe the system in longer wavelengths.

The result is unprecedented access to high resolution images that can continue to revolutionise the study of planet formation.

'We've discovered thousands of planets around other stars and a big surprise is that many of the orbits are much more elliptical than those found in our solar system,' said Dr Tamayo.

This and future Alma discoveries may be the key to connecting these discovered planets to their original birth locations.

Young stars are known to have disks of dust and gas in their vicinity, giving rise to planets, but until now no system had been spotted undergoing planet formation. Studying systems like HL Tau could help reveal if our own habitable solar system is unique or commonplace

While the HL Tau system remains stable in its relatively young age, Dr Tamayo says over billions of years it will act as a 'ticking time bomb.'

Eventually the planets will scatter, ejecting some and leaving the remaining bodies on elliptical orbits like the ones found around older stars.

Our solar system does not seem to have undergone such a dramatic scattering event, notes Dr Tamayo.

Future observations could also go a long way in determining whether our solar system is typical of others, or an oddity ideally suited for life.

'If further observations show these to be the typical starting conditions around other stars, it would reveal our solar system to be a remarkably special place,' said Dr Tamayo. 

The findings are due to be published in the Astrophysics Journal.