'Eye of Sauron' image reveals disc forming around alien planet

The striking image offers astronomers the opportunity to observe a system featuring both newly-forming planets and moons at the same time.

Friday 23 July 2021 15:51, UK

The 'Eye of Sauron' circumstellar disc around PDS 70. Pic: ESO
Image: The 'Eye of Sauron' circumstellar disc around PDS 70. Pic: ESO
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Scientists have captured an image of a circumstellar disc, and within it a planet with a moon-forming disc, that looks like the Eye of Sauron from the Lord of the Rings cinematic franchise.

Observations of the system, nearly 400 light years away in the constellation Centaurus, reveal a planet within the circumstellar disc called PDS 70c that has another disc around it, approximately 500 times larger than Saturn's.

The exoplanet was first directly imaged using infrared wavelengths in 2019, but a new observation from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile has revealed the construction in even more detail.

This image, taken with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, shows a close-up view on the moon-forming disc surrounding PDS 70c, a young Jupiter-like gas giant nearly 400 light-years away. It shows this planet and its disc centre-front, with the larger circumstellar ring-like disc taking up most of the right-hand side of the image. The dusty..circumplanetary..disc is as large as the Sun-Earth distance and has enough mass to form up to three satellites the size of the Moon.
Image: A close-up view on the moon-forming disc surrounding PDS 70c. Pic: ESO

The European Southern Observatory (ESO) has clarified that the ring visible in the "Eye of Sauron" image is not the new planetary disc, which is only visible as a spot of light in the image above.

PDS 70c is one of two Jupiter-like planets orbiting the star, but until recently astronomers were unsure whether the gas giants had discs forming around them or not.

"Our work presents a clear detection of a disc in which satellites could be forming," explained Dr Myriam Benisty, who led the research published in The Astrophysical Journal Letters.

"Our ALMA observations were obtained at such exquisite resolution that we could clearly identify that the disc is associated with the planet and we are able to constrain its size for the first time," Dr Benisty added.

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To date astronomers have discovered more than 4,000 exoplanets - planets orbiting distant stars - but all of them have been detected in mature systems.

The two planets, PDS 70b and PSD 70c, are the first to be discovered that are still in the process of being formed - meaning they offer astronomers insight into planet formation as well as how moons are made.

Radio telescope antennas of the ALMA (Atacama Large Millimeter/submillimeter Array) project, in the Chajnantor plateau, Atacama desert, some 1500 km north of Santiago, on March 12,2013. The ALMA, an international partnership project of Europe, North America and East Asia with the cooperation of Chile, is presently the largest astronomical project in the world. On Wednesday March 13 will be opened 59 high precision antennas, located at 5000 of altitude in the extremely arid Atacama desert. AFP PH
Image: ALMA's radio telescopes are perched high in Chile's Atacama desert

Planets are believed to form in the dusty discs surrounding young stars, carving out cavities in these discs as they gobble up material to grow.

In doing so, the planets can acquire their own discs which contributes to their growth by regulating the amount of material falling on to it.

"At the same time, the gas and dust in the circumplanetary disc can come together into progressively larger bodies through multiple collisions, ultimately leading to the birth of moons," explained ESO, although these processes are not yet fully understood.

The PDS system "offers us a unique opportunity to observe and study the processes of planet and satellite formation," explained ESO Research Fellow Stefano Facchini.