Free Astronomy Magazine May-June 2023

20 MAY-JUNE 2023 ASTRO PUBLISHING J. Tobin, an astronomer at the Na- tional Radio Astronomy Observa- tory, USA and lead author of the study published in Nature . This discovery was made by studying the composition of water in V883 Orionis, a planet-forming disc about 1300 light-years away from Earth. When a cloud of gas and dust col- lapses it forms a star at its centre. Around the star, material from the cloud also forms a disc. Over the course of a few million years, the matter in the disc clumps together to form comets, asteroids, and even- tually planets. Tobin and his team used ALMA, in which the European Southern Observatory (ESO) is a partner, to measure chemical signa- tures of the water and its path from the star-forming cloud to planets. Water usually consists of one oxygen atom and two hydrogen atoms. Tobin’s team studied a slightly heav- ier version of water where one of the hydrogen atoms is replaced with deuterium — a heavy isotope of hydrogen. Because simple and Missing link for water in the Solar System found by ESO - Juan Carlos Muñoz Mateos U sing the Atacama Large Mil- limeter/submillimeter Array (ALMA), astronomers have de- tected gaseous water in the planet- forming disc around the star V883 Orionis. This water carries a chemical signature that explains the journey of water from star-forming gas clouds to planets, and supports the idea that water on Earth is even older than our Sun. “We can now trace the origins of water in our Solar System to before the formation of the Sun,” says John