The planet that shouldn't exist: Bizarre world orbiting its star from a staggering distance leaves astronomers baffled



The 1,500°C planet, named HD 106906 b, is 11 times Jupiter’s mass



It orbits its star at 650 times the average Earth-Sun distance

According to current planet formation theories, this shouldn't be possible

The system has also sparked interest because there is a remnant ‘debris disk’ of material left over from planet and star formation

Astronomers have found a distant planet so strange, that according to current planet formation theories, it shouldn’t even exist.

The planet is 11 times Jupiter’s mass and orbits its star at an incredible 650 times the average Earth-Sun distance.

Named HD 106906 b, the planet is unlike anything in our own solar system and doesn’t fit with any existing planet formation theories.



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The planet, whose original name is HD 106906 b, was discovered by the University of Arizona earlier this year and has been baffling scientists ever since

It is thought that planets close to their stars, like Earth, are created from small asteroid-like bodies born in the primordial disk of dust and gas that surrounds a forming star.

However, this process acts too slowly to grow giant planets far from their star.

Another proposed mechanism is that giant planets can form from a fast, direct collapse of disk material.

But primordial disks rarely contain enough mass in their outer reaches to allow a planet like HD 106906 b to be created.

Planet HD 106906 b is shown in thermal infrared light. The planet is more than 20 times farther away from its star than Neptune is from our sun

THE 'IMPOSSIBLE' PLANET

HD 106906 b is 11 times Jupiter’s mass and orbits its star at an incredible 650 times the average Earth-Sun distance. At only 13 million years old, this young planet still glows from the residual heat of its formation. It has a temperature of 2,700 Fahrenheit (about 1,500 °C) making it much cooler than its host star. It emits most of its energy as infrared rather than visible light. Earth, by comparison, formed 4.5 billion years ago and is about 350 times older.



Several alternative theories have been put forward, including formation like a mini binary star system.

‘A binary star system can be formed when two adjacent clumps of gas collapse more or less independently to form stars, and these stars are close enough to each other to exert a mutual gravitation attraction and bind them together in an orbit,’ said Vanessa Bailey, a student at Arizona University who led the research.

‘It is possible that in the case of the HD 106906 system the star and planet collapsed independently from clumps of gas.’

One problem with this scenario is that the mass ratio of the two stars in a binary system is typically no more than 10-to-1.

‘In our case, the mass ratio is more than 100-to-1,’ she explained. ‘This extreme mass ratio is not predicted from binary star formation theories – just like planet formation theory predicts that we cannot form planets so far from the host star.’

The team was able to confirm that the planet is moving together with its host star by examining Hubble Space Telescope data taken eight years prior for another research programme

This system has also sparked interest because researchers can still detect the remnant ‘debris disk’ of material left over from planet and star formation.

‘Systems like this one, where we have additional information about the environment in which the planet resides, have the potential to help us disentangle the various formation models,’ said Ms Bailey added.

‘Future observations of the planet's orbital motion and the primary star's debris disk may help answer that question.’

At only 13 million years old, this young planet still glows from the residual heat of its formation.

It has a temperature of 2,700 Fahrenheit (about 1,500°C) making it much cooler than its host star. It emits most of its energy as infrared rather than visible light.

Earth, by comparison, formed 4.5 billion years ago and is about 350 times older than HD 106906 b.

The team was able to confirm that the planet is moving together with its host star by examining Hubble Space Telescope data taken eight years prior for another research programme.