For ten years, the Alma radio telescope network has focused its gaze on protoplanetary disks that are at most about ten million years old and surround young stars. Researchers use this information to understand the formation of exoplanets and even the formation of the solar system. For the first time, Alma observes the beginnings of planet formation around the protostar DG Tau and thus questions cosmogonic models.
This will also interest you
[EN VIDÉO] The planets of the solar system were born from cataclysms. The Earth and the other planets that revolve around the Sun were born in turmoil.
In 2013, the Atacama Large Millimeter/Submillimetre Array, one of the highest astronomical observatories on earth, was inaugurated on the Chajnantor plateau at an altitude of 5,000 meters. in the Chilean Andes. Alma is a network of radio telescopes capable of observing some of the coldest objects in the universe in the millimeter and submillimeter radiation ranges, from infrared to radio waves.
This allows Alma to explore the mysteries of planet birth in the protoplanetary disks, where planets form according to standard cosmogonic theory. These disks are initially formed by the accretion of gas and dust into a cold, dense molecular cloud that can collapse under its own gravity, forming a protostar in which the pressure heats matter to ultimately ignite thermonuclear fusion reactions.
ESOcast 69 presents the result of Alma observations that reveal exceptionally fine details never before seen in the planet-forming disk around the young star HL Tauri. This is the sharpest image ever captured in the submillimeter wavelength range. To get a reasonably accurate French translation, click on the white rectangle at the bottom right. Make sure that English subtitles are displayed and finally click “Auto translate”. Select “French”. © European Southern Observatory (ESO)
From HL Tauri to DG Tau
Alma has been providing us with images of these records at various points in their development for about a decade. As explained in the video above, the dust in the protoplanetary disks sticks together and ends up forming pebbles and boulders larger than a meter, which attract each other, thus forming small planetary bodies and embryos of planets that increase in size . This will create areas poor in gas and dust in their orbits.
But if we are to believe an international team of astronomers led by Satoshi Ohashi of the National Astronomical Observatory of Japan (Naoj), Alma has made it possible to delve deeper into the past of the formation of the solar system’s planets or the known exoplanets in the Milky Way Observation of a protostar called DG Taurus (DG Tau).
Like HL Tauri, it is located in the famous Taurus Molecular Cloud 1 (TMC-1), about 450 light-years from Earth in the constellation Taurus.
In an article published in the Astrophysical Journal, but also freely available to read on arXiv, the researchers explain that, unlike HL Tauri, the protoplanetary disk of DG Tau appears smooth and without ring structures associated with planets. This is a remarkable discovery as it has previously proven difficult to find a blank CD without such signatures.
Cosmogonic models for review
Planetary scientists specializing in cosmogony conclude that we are likely observing DG Tau’s protoplanetary disk at the very beginning of the birth of planets and that it is therefore an open window into the physical and cosmochemical mechanisms at work. “There are no signs of planet formation. We believe that this study is very important because it reveals the initial conditions of planet formation,” commented Satoshi Ohashi in a Naoj press release, which stated: “The results interestingly suggest that the outer regions of the disk of the of planet formation, which challenged previous assumptions that the inner disk was the primary starting point. Remarkably, the midplane of the disk had a high dust-to-gas ratio, suggesting that the disk would soon be ready to form planets.”
To uncover these mysteries, astronomers observed the disk at different wavelengths (0.87 mm, 1.3 mm and 3.1 mm) and examined the intensity of the radio waves and their polarization. Depending on the size and density of the dust, the ratio of the intensities of radio waves of different wavelengths and the polarization intensity of the radio waves scattered by the dust changes. The size and density distributions of the dust grains could then be estimated by comparing the results of the numerical simulation observations with different models of the size and density distribution of dust in the protoplanetary disk around the protostar.
The solar system is a laboratory for studying the formation of giant planets and the origin of life, which can be used in conjunction with the rest of the universe and observed for the same purpose. Mojo: Modeling the Origin of JOvian planets is a research project that resulted in a series of videos presenting the theory of the origin of the solar system and in particular the gas giants by two renowned specialists, Alessandro Morbidelli and Sean Raymond. To get a reasonably accurate French translation, click on the white rectangle at the bottom right. English subtitles should then appear. Then click on the nut to the right of the rectangle, then click on “Subtitles” and finally “Auto-translate”. Select “French”. © Laurence Honnorat
Did you know ?
How did the solar system form? At the beginning of the 20th century, many cosmogonic theories on this subject were already proposed by the scientific community, theories that were masterfully expounded in Poincaré’s treatise. But it was only in the 1960s to 1970s that significant progress was made in answering this question, within the framework of theories developed first and foremost by the Russian Viktor Safronov and the American George Wetherill.
This led to a scenario of planet formation based on solar system physics and chemistry that is now broadly accepted and further supported by observations of young exoplanetary systems in the process of forming. A good presentation offers a series of videos with explanations by Alessandro Morbidelli, Italian astronomer and planetary scientist from the Côte d’Azur Observatory, best known for his work on solar system dynamics, and Sean Raymond, researcher at the Bordeaux Astrophysics Laboratory, who is also known for his work in this field.