Disk migration occurs when a newly formed planet interacts with the gas and dust disk that surrounds its parent star. The planet's gravity can exert a drag on the disk, causing it to spiral inward toward the star. As the planet moves closer to the star, it heats up due to the increased radiation it receives.
This heating can cause the planet's atmosphere to expand, making it more susceptible to further heating. In some cases, the planet's atmosphere can become so hot that it begins to glow, making it visible to telescopes.
Another possibility is that hot Jupiters form through a process called tidal heating. Tidal heating occurs when a planet's orbit is eccentric (i.e., not circular). As the planet moves closer to and farther from its parent star, its gravitational pull on the star changes. This changing gravitational pull can cause the star to deform, which in turn generates heat. This heat can be transferred to the planet, causing it to become hot.
A combination of both inward migration and tidal heating is also a possible mechanism for the formation of hot Jupiters.
So, while it's not a simple answer, the most widely accepted theory is that hot Jupiters form through a combination of disk migration and tidal heating, resulting in a planet that is very close to its star and extremely hot.
