We can measure where and how water formed based on hydrogen isotopes. Normal hydrogen has no neutrons in its nucleus while heavy hydrogen or deuterium has one neutron in its nucleus. Water molecules that contain heavy hydrogen are also known as heavy water. Heavy water is formed in different conditions from normal water.
Here on Earth, some traces of water reach comets because the isotope ratio of water is similar to that of heavy water. In this way, water can be collected in comets and asteroids and then transferred to planetary masses; But how water enters comets has not yet been fully explained. Tobin and his team have solved this mystery by examining the star V883 Orionis. Tobin says:
According to Tobin, the star V883 Orionis is like a missing link. The composition of water in the disk is very similar to the composition of water in the comets of the solar system. This evidence supports the hypothesis that water in star systems formed in interstellar space billions of years before the Sun, and that both comets and Earth inherited it relatively unchanged.
V883 Orionis is a special star due to its high growth rate and hotter than usual temperature. Most of the water in accretion disks around protostars is frozen and is only visible as vapor near the star. The sharp increase in activity of V883 Orionis has caused its freezing point to reach a point further than usual. Any water closer to that freezing point is in vapor form.