High-mass stars are incredibly hot, with surface temperatures ranging from 25,000 to 50,000 Kelvin (K). This is significantly hotter than our Sun, which has a surface temperature of about 5,500 K.

Here's a breakdown:

* Surface temperature: This is the temperature of the star's visible surface, which we can measure directly using spectroscopy.

* Core temperature: The core of a high-mass star is even hotter, reaching millions of Kelvin. This extreme heat is what drives the nuclear fusion processes that power the star.

Key points to remember:

* High-mass stars are much hotter than low-mass stars.

* Their high temperatures are a direct result of their large mass and the intense nuclear fusion occurring within their cores.

* The temperature of a star influences its color, with hotter stars appearing bluer and cooler stars appearing redder.

Let me know if you have more questions about high-mass stars or other celestial objects!