Hear the Sounds of Planet 9 in New Symphony

In 2016, Caltech planetary scientists Konstantin Batygin (PhD '12) and Mike Brown proposed evidence for a new planet five to 10 times the size of Earth and lurking over 20 billion miles from the Sun (10 times farther than Neptune's orbit). The duo called the unseen body "Planet 9."

On May 17 and 18, the public can hear a symphony inspired by the Planet 9 hypothesis. Composed by Miami Symphony conductor Eduardo Marturet and performed by the Caltech orchestra, the piece features a guitar solo played by Batygin.

Marturet and Batygin met in 2017 after both received awards from the Genius 100 Foundation. They struck up a friendship, and Marturet was inspired by Batygin's research to write an extension of Gustav Holst's classic 1918 symphony The Planets, which features seven movements inspired by the solar system, to include Planet 9.

"The symphony masterfully portrays the intellectual tug-of-war inherent in theoretical work—exploring the gravitational dynamics of our solar system with both struggle and exultation," remarks Batygin. "It also embraces a more avant-garde narrative, reflecting the thrill of the hypothesis evolving beyond its origins, almost taking on a life of its own."

The emotional roller coaster of joy and sorrow has been palpable. In the eight years since Brown and Batygin first proposed the hypothesis, the quest for Planet 9 has intensified. Researchers have refined the original evidence and bolstered it with sophisticated numerical models of the underlying physical mechanisms. Despite these efforts, Planet 9 has evaded direct discovery.

However, this month, Batygin and Brown, along with Alessandro Morbidelli at Collège de France and David Nesvorny at the Southwest Research Institute, have demonstrated a new line of evidence for Planet 9's existence—and it is the most statistically significant evidence to date. In a new paper titled "Generation of Low-Inclination, Neptune-Crossing TNOs by Planet Nine," the team predicted that if Planet 9 exists at its proposed mass and orbit, its gravitational influence must give rise to a distinct population of long-period trans-Neptunian objects, bodies whose orbits cross through the orbit of Neptune. By comparing the observed census of 17 such objects with the most advanced Planet 9 simulations to date, the team demonstrated that these objects' orbits could not be attributed to other effects, such as the galactic tide or passing stars. The compelling alignment of observational data with the theoretical predictions of the Planet 9 hypothesis, on the other hand, robustly supports the object's presence in our solar system.

"[Konstantin's] expertise and passion for exploring the cosmos infused the composition with a sense of wonder and curiosity," says Marturet. "His contributions serve as a reminder of the boundless creativity and innovation that emerge when different disciplines intersect."

The two performances of the Planet 9 symphony are free and open to the public. More information can be found here: /campus-life-events/calendar/caltech-orchestra-17 and /campus-life-events/calendar/caltech-orchestra-18