A "Hot Jupiter" is a type of exoplanet that is similar in size and composition to Jupiter, but orbits very close to its parent star. This proximity results in extremely high surface temperatures, often exceeding 1,000 degrees Celsius. Hot Jupiters are gas giants, primarily composed of hydrogen and helium, and they typically have short orbital periods, completing a full revolution around their star in just a few days. These planets challenge traditional theories of planet formation, as they are found in orbits much closer than what was previously thought possible for such large bodies. The discovery of Hot Jupiters has led to new insights into planetary migration and the dynamics of solar systems.