Some constellations, such as Ursa Minor, are visible in the sky year-round; other constellations appear for only part of the year. Explain why this happens.
could it be the axis tilt of Earth doesn't always point the same way at night? Think about that.
facepalm
The visibility of constellations throughout the year is influenced by two main factors: the rotation of the Earth on its axis (daily motion) and its orbit around the Sun (annual motion).
First, let's consider the daily motion of the Earth. As the Earth rotates on its axis, different parts of the sky become visible to us at different times. This means that throughout the night, various constellations will rise above the horizon, move across the sky, and eventually set below the horizon. This daily rotation of the Earth causes the appearance of constellations to change in the sky.
Now, let's discuss the annual motion of the Earth around the Sun. As the Earth orbits the Sun, the position of the Sun in our sky changes over the course of a year. This apparent movement of the Sun creates our seasons. As the Earth travels around the Sun, we observe different constellations at different times of the year because our perspective changes. For example, when the Earth is on the opposite side of the Sun compared to a specific constellation, that constellation will not be visible in our night sky because it is blocked by the glare of the Sun.
Combining the daily and annual motions, we can understand why some constellations are visible year-round while others have limited visibility. Constellations that are visible all year round, such as Ursa Minor (which contains the North Star, Polaris), are located near the celestial North Pole or celestial South Pole. These constellations appear stationary as they are positioned close to the Earth's axis of rotation. Therefore, they can be seen from the same location throughout the year, regardless of the Earth's position in its orbit around the Sun.
On the other hand, constellations that have limited visibility are located closer to the Sun's path in the sky known as the ecliptic. Since the Earth's orbit is inclined relative to the equator, the Sun's apparent path in our sky also appears to be inclined compared to the celestial equator. As a result, constellations located near the ecliptic are only visible during specific times of the year when they are not hidden by the Sun's glare. An example of such a constellation is Orion, which is a prominent winter constellation in the Northern Hemisphere.
Overall, the combination of the Earth's rotation and its orbit around the Sun determines the visibility and appearance of constellations throughout the year.