NASA's Webb Redefines Dividing Line Between Planets, Stars

Where is the dividing line between stars and the most massive planets? Scientists think it may depend on how they formed. Was it from a bottom-up approach, gradually growing larger over time, or a top-down approach in which a large collection of gas and dust fragments into smaller, planet-sized bits?

To answer these questions, astronomers used the James Webb Space Telescope to study an object weighing about 15 times as much as Jupiter, which puts it right on the dividing line between the two processes. They found that the object, called 29 Cygni b, likely formed from the bottom up rather than the top down. In other words, it formed like a planet, not a star.