What To Know
- If it exists, Planet 9 would indeed be located at least 500 astronomical units from the sun, or about 500 times the distance from Earth to the Sun, which means that its light would be extremely weak and difficult to detect.
- Rubin Observatory is to conduct the Legacy Survey of Space and Time (LSST), a synoptic survey that will map the entire visible sky several times a night for a period of 10 years.
- By studying the extreme conditions at the outer reaches of the Solar System, astronomers could indeed better understand the mechanisms of planet formation on a galactic scale, enriching our understanding of….
The Planet 9 Hypothesis
The solar system currently has eight planets official: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. However, for several years, astronomers have been postulating the existence of a ninth world, nicknamed “Planet 9”. This hypothetical planet, which would be a gas or ice giant, would be billions of kilometers beyond Neptune and could be about seven times more massive than Earth. The Planet 9 hypothesis is based on gravitational anomalies observed as early as 2004 in the orbits of certain trans-Neptunian objects (TNOs), such as Sedna and 2012 VP113. In 2016, Mike Brown and Konstantin Batygin, astronomers at Caltech, then concluded that there was only a 2% chance that these orbits were due to chance. Their study then suggested that a massive planet could be responsible for these gravitational anomalies. Since then, several other TNOs with eccentric orbits have been discovered, adding evidence to the Planet 9 hypothesis. 
Based on its distance from the Sun, Planet 9 likely has a composition similar to Uranus (left) and Neptune (right).Credit: NASA
A needle in a huge haystack
Despite these clues, the object remains elusive. And for good reason, its tracking is compromised by several factors. Its distance from the sun is probably the most important. If it exists, Planet 9 would indeed be located at least 500 astronomical units from the sun, or about 500 times the distance from Earth to the Sun, which means that its light would be extremely weak and difficult to detect. Furthermore, astronomers only have a rough idea of the possible orbit of Planet 9. We simply know that this orbit is immense and very distant. This object could therefore be located anywhere along this trajectory, which makes its location extremely difficult. This vast region of space to explore then means that astronomers must analyze a huge portion of the sky to try to spot this hypothetical planet. Naturally, doubts also remain among the scientific community. Some researchers suggest that the observed orbital anomalies could be due to observational bias or other phenomena, such as dust disks or even a small black hole. Others think that our model of gravity could need adjustments. Still, efforts to locate this planet continue. In fact, one telescope in particular could soon change that.
See you in 2025
The Vera C. Rubin Observatory, formerly known as the Large Synoptic Survey Telescope (LSST), is an astronomical observatory under construction atop Cerro Pachón in Chile. Scheduled to begin operations in 2025, it is set to revolutionize our understanding of the Universe with its cutting-edge instruments and innovative approach to observing the sky. The Vera C. Rubin Observatory will notably be equipped with an 8.4-meter-diameter telescope and a 3.2-gigapixel digital camera, the largest ever built for an optical telescope. This camera will capture extremely detailed images of the night sky. One of the main objectives of the Vera C. Rubin Observatory is to conduct the Legacy Survey of Space and Time (LSST), a synoptic survey that will map the entire visible sky several times a night for a period of 10 years. Thanks to its ability to quickly scan vast regions of the sky, the observatory will be particularly well suited to searching for distant and faint objects like Planet 9. 
Astronomers believe that the future Vera C. Rubin Observatory in Chile will finally allow them to see Planet Nine. Credit: Olivier Bonin/SLAC National Accelerator Laboratory
The importance of Planet 9
Although they remain divided on its existence, scientists all agree on one thing: the discovery of Planet 9 would likely be the greatest astronomical discovery of the century. Beyond the surprise, its existence could challenge and deepen our understanding of the formation of giant planets like Jupiter and Saturn. Its presence would also have profound implications for models of planetary migration and solar system dynamics, providing new insights into the history of our own stellar system. Furthermore, the search for Planet 9 could provide crucial answers about the formation and evolution of exoplanets in other stellar systems. By studying the extreme conditions at the outer reaches of the Solar System, astronomers could indeed better understand the mechanisms of planet formation on a galactic scale, enriching our understanding of the diversity and distribution of exoplanets. Of course, the potential impact of the discovery of Planet 9 would not be limited to astronomical theory; It could also catalyze a new era of space exploration. Confirmation of its existence would likely spark increased interest in space missions dedicated to studying it directly. These missions could not only map its structure and composition, but also probe the secrets of its icy environment and assess its impact on the overall dynamics of the solar system. Ultimately, while the search for Planet 9 is currently shrouded in mystery and debate, its eventual discovery could open extraordinary opportunities for astronomy and space science. It could not only transform our understanding of the past and future of our solar system, but also inspire a new generation of discovery and exploration beyond the boundaries of our own planetary system. Source: space.com
