The Origin of Water in Planetary Systems: Evidence from V883 Orionis
V883 Orionis, a star located 1,300 light-years away from Earth, may have just uncovered one of the secrets of the Solar System.
This young star is surrounded by a vast disk of material that will eventually come together to form orbiting planets. In this disk, scientists have detected water vapor, swirling around with other dust and gas that will become part of an alien world.
This discovery implies that the water present in the Solar System, including the water on Earth, was already present in the gaseous environment where the Sun was born. In other words, water was present before the Sun and played a role in the formation of our planet.
Although water is common in the Universe, it is particularly important to Earth. It exists in various forms, such as vapor in the atmosphere, rivers, lakes, and oceans. Water is essential for almost all chemical processes required for life.
Water also plays a crucial role in planet formation. Stars originate from clouds of dust and gas in space. When a dense clump of material collapses under gravity and begins spinning, it pulls in more material from the surrounding cloud to form a disk that eventually feeds into the baby star.
After a star has stopped growing, the remaining material in the disk forms the other features of the planetary system. Dust particles come together and form larger clumps through electrostatic forces until gravity takes over.
Water is believed to be an important factor in this process. At the snowline, where water vapor freezes, it coats dust particles as ice. This provides an additional adhesive force that helps particles stick together during the initial stages of planetary formation.
Scientists can determine where and how water forms by examining the isotopes of hydrogen. Hydrogen without neutrons is called normal hydrogen, while hydrogen with one neutron is called heavy hydrogen or deuterium. Heavy water, which includes heavy hydrogen, forms under different conditions than normal water.
The similarity in the water-to-heavy water isotope ratios of comets and Earth suggests that comets and asteroids may have delivered water to Earth. However, the origin of the water in comets was previously unknown. By studying V883 Orionis, Tobin and his team have been able to fill in that gap.
Tobin explains that tracing the path of water through the Universe is like following a trail, and they wanted to trace it back to its origins. Prior to this discovery, they could link Earth to comets and protostars to the interstellar medium, but they couldn’t link protostars to comets. V883 Orionis has changed that and demonstrated that water molecules in the system and the Solar System have similar hydrogen isotope ratios.
V883 Orionis is still young and growing, surrounded by a vast disk. By examining the light emitted by the disk, scientists have identified the spectral signature of water vapor and the hydrogen isotope ratios.
V883 Orionis is an important discovery because it helps to fill in a gap in our understanding of how water forms in the Universe. By studying the spectral signature of the star’s surrounding disk, scientists have found unambiguous evidence of water vapor in the material that will eventually coalesce into planets. This discovery suggests that the water in our Solar System, including that on Earth, was present in the gaseous cradle from which the Sun was born, and helped our planet grow.
Water is important for life on Earth, and also plays a significant role in the formation of planets. Dust grains in the disk surrounding a young star stick together to form larger clumps until the object is massive enough for gravity to take over. Water vapor freezes beyond the snowline and coats dust grains as ice, giving them an additional stickiness that helps particles cling together in the early stages of planetary growth.
Isotopes of hydrogen can help us trace the origins of water in the Universe. By studying the water-to-heavy water isotope ratios, scientists can determine where and how water forms. The water-to-heavy water isotope ratios in comets are similar to those on Earth, suggesting that water can be bound up in comets and asteroids and delivered to planetary bodies. V883 Orionis has helped fill in the gap in our understanding of how water gets into comets.
The composition of the water in V883 Orionis’s disk is similar to that of comets in our own Solar System, providing confirmation that water in planetary systems formed billions of years ago, before the Sun, in interstellar space, and has been inherited by both comets and Earth, relatively unchanged. V883 Orionis is special because it’s been undergoing a burst of accelerated growth, which has pushed its snowline out to a point much farther from the star than usual, making it easier to detect and analyze the water vapor in its disk. The researchers have found over 1,200 times the volume of Earth’s oceans drifting as vapor around V883 Orionis.
The research findings show that water in a planetary system primarily comes from the clouds where its star forms. The team of researchers concluded that the water in large icy bodies like comets originates from the star-forming cloud and is incorporated without significant changes. The specific method of how water arrived on Earth, whether through comets or asteroids, is still being debated, but the hydrogen isotope ratio discovered in V883 Ori proves that water molecules in our Solar System originated in the cold interstellar medium before the Sun’s formation. Therefore, it is essential to observe water in young planet-forming disks to understand the connection between the water reservoir and the formation of terrestrial planets.
The research has been published in Nature.
https://www.nature.com/articles/s41586-022-05676-z
