Astronomy Test (Homework)

Celestial Sphere/ Celestial Equator and Ecliptic

The celestial sphere is an imaginary sphere surrounding Earth used as a model of the sky. The celestial equator is Earth's equator projected onto the sky. The ecliptic is the Sun's apparent yearly path through the stars

rotation and revolution

Rotation is an object's spin around its own axis. Revolution is an object's motion around another object.

Seasons

Earth's 23.5° axial tilt combined with its revolution around the Sun causes the seasons. The tilt changes the amount and intensity of sunlight and the length of daylight received by each hemisphere during the year.

If Earth's orbit were a perfect circle, would we still have seasons? Why or why not?

Yes. We would still have seasons because they are caused by Earth's axial tilt, not changes in Earth's distance from the Sun.

Why does the Sun look slightly larger in January than it does in July?

Earth is closer to the Sun in January (perihelion) and farther away in July (aphelion), so the Sun appears slightly larger in January.

Why does the Moon look larger when it is near the horizon than when it is high at its zenith?

This is called the Moon illusion. The Moon isn't actually larger; it appears larger near the horizon because the brain compares it with familiar objects such as trees and buildings.

The average distance from Earth to the Sun is 1 AU, or roughly 1.5 × 10⁸ kilometers. If a planet is 5.2 AU from the Sun, what is its distance in kilometers?

5.2 × 1.5 × 10⁸ km = 7.8 × 10⁸ km, or 780,000,000 km.

The angular diameter of the full Moon is about 0.5 degrees. How many arcminutes is this?

1° = 60 arcminutes.
0.5 × 60 = 30 arcminutes.