450P/LONEOS observed transforming from a frozen centaur into an active comet

Astronomers have observed the first direct transformation of a frozen celestial body, known as a “centaur,” into an active comet. The object, identified as 450P/LONEOS and discovered in 2004, orbits between Jupiter and Neptune.

Orbital analysis indicates that the object's trajectory changed in 1992 after passing approximately 4.6 million kilometers from Saturn. The gravitational influence of the gas giant pushed the object into a tighter orbit closer to the Sun. As it approached the Sun, the increasing heat caused frozen layers on its surface to sublimate.

Observations from the Gemini North Telescope in Hawaii and data from the James Webb Space Telescope revealed a cloud of gas and dust forming around the core. Scientists determined that because of the object's distance from the Sun, water vapor was not present; instead, the comet-like activity was triggered directly by the release of carbon dioxide gas and crystallized ice particles. This discovery provides critical insights into the evolution of primitive icy bodies that have remained largely unchanged since the formation of the solar system 4.5 billion years ago.