For the first time, astronomers have reliably registered the presence of a dusty Moon-forming disc around a protoplanet in an exoplanetary system. This was done thanks to the ALMA radio telescope, which observed the system of the young star PDS 70.
How did astronomers find a Moon-forming disc in deep space?
1. The task of searching for protoplanets located in gas and dust discs around young stars is extremely important for exoplanetology since observations of such objects make it possible to refine the models of the formation and growth of both exoplanets themselves and their satellites – exomoons.
2. However, direct observations of protoplanets are quite difficult, mainly scientists find candidates for gas giants in the infrared range at large distances from stars.
3. To date, the most reliable case for detecting protoplanets in the circumstellar disc is the system of a young low-mass star PDS 70, which belongs to the T Tauri type and is located 370 light-years from the Sun.
4. In 2018, astronomers received the first-ever direct image of a protoplanet and later found the second protoplanet in the system. PDS 70b is at an average distance of 22 astronomical units from the star, and PDS 70c is 34 astronomical units from the star, both planets have masses of less than 10 Jupiter masses.
5. A group of astronomers led by Myriam Benisty of the University of Grenoble in France has published the results of observations of the PDS 70 using the ALMA radio telescope system, the purpose of which was to study the features of the system from high-resolution images. The observations were carried out at a wavelength of 855 micrometers and made it possible to distinguish details up to 2.3 astronomical units in size.
6. Scientists have found a compact radiation source located near the protoplanet PDS 70c and separated from the moon-forming disc. Its radius has been estimated at less than 1.2 astronomical units.
7. If we assume that the radiation is generated by dust grains with a size of 1 micrometer or 1 millimeter, then the mass of dust in the found source will be 0.031 or 0.007 of the Earth’s mass, respectively.
8. The researchers came to the conclusion that for the first time they are observing a circumplanetary disc, the substance in which may be enough to create three satellites of the planet.
9. Astronomers have also discovered an extended and fainter source of radiation near the protoplanet PDS 70b, which can be interpreted as a more diffuse moon-forming disc.
10. Scientists hope that further studies of the gas kinematics and the chemical composition of the PDS 70 disc will improve the models for the formation of satellites, the interaction of planets and discs, and the delivery of various substances into the atmospheres of young planets.
See the video below for a breathtaking journey through space all the way to the PDS 70 system where astronomers observed a Moon-forming disc around a protoplanet for the first time in history.
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• Dobrijevic, D. (2021, July 22). Astronomers spot 1st moon-forming disk around an alien world. Space.com.
• ESO. (n.d.). Astronomers make first clear detection of a moon-forming disc around an exoplanet.
• Phys.org. (2021, July 22). Astronomers make first clear detection of a moon-forming disc around an exoplanet.