Stars don't actually move across the sky in the way we perceive them to. The apparent movement is due to the Earth's rotation.

Here's a breakdown:

* Earth's Rotation: Our planet spins on its axis, completing one rotation roughly every 24 hours. This rotation causes the apparent movement of celestial objects, including stars, across the sky.

* Angular Speed: The apparent speed of a star's movement depends on its declination (its angular distance from the celestial equator). Stars near the celestial equator appear to move faster than stars further north or south.

* Approximate Speed: A star near the celestial equator will appear to move about 15 degrees across the sky each hour. This is because the Earth rotates 360 degrees in 24 hours, which translates to 15 degrees per hour.

Important Note: This is just an approximation. The exact apparent speed of a star's movement across the sky can vary slightly based on its declination and the observer's location on Earth.