Astronomers have discovered a new link between water and planetary formation

Researchers have discovered water vapor in the disk surrounding a young star, specifically in the region where planets might form. In addition to being an essential element for life on Earth, water is also thought to play an important role in planetary formation. However, until now, we have never been able to map how water is distributed in a cool, stable disk, the type of disk that provides the most favorable conditions for planets to form around stars. The new results were obtained with the help of the Atacama Large Millimeter/submillimeter Array (ALMA), of which the European Southern Observatory (ESO) is a partner.

says Stefano Facchini, an astronomer at the University of Milan in Italy, who led the study published today in the Journal of Natural Astronomy. Observations reveal that there is at least three times more water than all of Earth's oceans in the inner disk of HL Tauri, a young, Sun-like star located 450 light-years from Earth in the constellation Taurus.

“It is truly remarkable that we can not only detect, but also obtain detailed images and spatially resolve water vapor at a distance of 450 light-years,” adds co-author Leonardo Testi, an astronomer at the University of Bologna in Italy. ALMA's “spatially resolved” observations allow astronomers to determine the distribution of water in different regions of the disk. “Participating in such an important discovery in the famous HL Tauri disk was much more than I expected in my first research experience in astronomy,” adds Mathieu Vander Doncht from the University of Liège in Belgium, who was earning his master's degree when he participated in this research. a job.

A large amount of water has been found in the region where there is a known gap in the HL Tauri disk. These ring-shaped voids are “sculpted” into gas- and dust-rich disks by young planet-like objects orbiting their parent star as they accrete material and grow. “Our recent images reveal a large amount of water vapor at a great distance from the star, including the space where a planet may currently be forming,” Facchini says, suggesting that this water vapor could affect the chemical composition of the planets in which they live. It is formed in these areas.

Observing water with a telescope placed on the Earth is not an easy task, as water vapor, which is abundant in the Earth's atmosphere, leads to the analysis of astronomical signals. Hey spirit, operated by ESO with its international partners, is a network of telescopes installed in the Chilean Atacama Desert, at an altitude of about 5,000 metres, which were built in a high and dry environment specifically to reduce this degradation to a minimum, and provide the conditions for exceptional observation. “So far, ALMA is the only infrastructure we have capable of spatially resolving water in a cold, planet-forming disk,” says co-author Wouter Flemmings, a professor at Chalmers University of Technology in Sweden.

“It's really exciting to see directly, in the image, water molecules being released from icy dust particles,” says Elizabeth Humphreys, an astronomer at the European Southern Observatory who was also involved in this study. The dust grains that make up the disk are seeds Planetary formationThey collide and clump to form larger objects orbiting the star. Astronomers believe that in places cold enough, where water freezes on dust grains, molecules stick together more efficiently, an ideal place for planets to form. “Our results show how the presence of water can influence the evolution of a planetary system, as happened about 4.5 billion years ago in our solar system,” Facchini adds.

with Ongoing updates at ALMA With the Very Large Telescope (Elt) When the European Southern Observatory becomes operational before the end of this decade, planetary formation and the role that water plays in that formation will become clearer than ever before. In particular, the instrument Metis(Mid-infrared ELT Imager and Spectrograph), will give astronomers an unparalleled view of the interior regions of planetary disks, the places where planets like Earth form.

European Southern Observatory