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ALMA reveals a disk that forms moons around a distant planet


Moon The disc formation was discovered around a distant planet

The color image of millimeter radio signals from the ALMA Observatory in Chile shows the gas and dust disk (right of the center) around the exoplanet PDS 70 c, the first observation of the circular disc type, which is believed to have been born by Jupiter more than 4 billion years ago. (Picture approved by A. Isella, ALMA (ESO / NAOJ / NRAO))

By using the strongest terrestrial spectrum of radio telescopes, astronomers made the first observations of a circular disk of gas and dust, such as those assumed to have produced Jupiter's moons.

The report, published today on the Astrophysical Journal Letters website, adds an interesting story about the planet PDS 70 c, a gaseous giant that still creates about 370 light-years from Earth and was first revealed last month in visible light images.

Using the massive 66-antenna Atacama Large Millimeter / submillimeter ArrayALMA) In Chile, the astronomer of the University of Rice, Andrea Isella and colleagues, collected radio signals of the millimeter wave that revealed the presence of dust grains throughout the star system, where PDS 70 c and its sister PDS 70 b.

"Planets are formed from disks of gas and dust around newly formed stars, and if the planet is large enough, it can shape its disc when it collects material in its orbit around the star," said Isella. "For example, Jupiter and its moons are, for example, a small planetary system in our solar system, and believe that the Jupiter's moons originated from a circular disk when Jupiter was very young."

A moon-shaping disc has been discovered

Radio astronomers using a large millimeter / submillimeter series of telescopes in Chile discovered a disc of gas and dust (left) around an exoplanet PDS 70 c, a still-formed gaseous giant that was obscured from the point of view in the infrared picture 2018 (right) which first revealed its sister planet PDS 70 b. (Picture approved by A. Isella, ALMA (ESO / NAOJ / NRAO))

But most planetary design models show that round diskettes disappear in 10 million years, which means that there are no more than 4 billion years in our solar system. To search for them elsewhere and collect observational evidence to test the theory of planet formation, Isella and colleagues are looking for very young star systems where they can directly observe disks and planets that are still formed in them. In a new study, Isella and colleagues analyzed the observations carried out by ALMA in 2017.

"There are quite a few candidate planets found on the discs, but this is a very new area that is still being discussed," said Isella. "(PDS 70 b and PDS 70 c) are amongst the most robust because they were independent observations with different instruments and techniques."

The PDS 70 is a dwarf star, which has about three quarters of the mass of the sun. Both of its planets are 5-10 times larger than Jupiter, while the deepest PDS 70b rotates about 1.8 billion miles from the star, which is about a distance from the Sun to Uranus. The PDS 70 c is a billion miles away, in the orbit of the size of Neptune.

The PDS 70 b was first disclosed in 2018 in infrared light fixtures from a planet-hunting instrument called SPHERE in the very large telescope (VLT) of the European Southern Observatory. In June, astronomers used another VLT instrument called MUSE to observe the visible wavelength of light known as H-alpha, which is emitted when hydrogen falls to a star or planet and becomes ionized.

"H-alpha gives us more confidence that these are planets, because it shows that they are still pumping gas and dust and growing," said Isella.

Observations of ALMA in millimeter wavelength provide even more evidence.

"Optical data is free and provides a completely independent confirmation that there is something," he said.

Isella said that direct observation of planets with circular disks would allow astronomers to test theories about the formation of planets.

"There is much that we do not understand about how the planets form, and now we have finally instruments for direct observation, and we begin to answer questions about how our solar system was designed and how other planets can be formed."

Isella is an assistant in physics and astronomy and earth, environmental and planetary science at Rice, and co-creator of the NASA-funded CLEVER Planets project.

The co-authors of the study are Myriam Benisty of Universidad de Chile and Université Grenoble Alpes, Richard Teague of the University of Michigan, Jaehan Bae of the Carnegie Institution for Science, Miriam Keppler of the Astronomy Max Planck Institute, Stefano Facchini of the European Southern Observatory and Laura Pérez with the Universidad de Chile.

The research was supported by the National Science Foundation, the French National Research Agency, NASA, the Chilean National Commission for Scientific and Technological Research, the Chilean National Science and Technology Fund, the Horizon of the European Union 2020 and the European Southern Observatory.

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