Astronomy and Cosmology

A typical galaxy, such as our Milky Way, contains anywhere from tens of billions to hundreds of billions of stars. Dwarf galaxies may have hundreds of millions, while giant galaxies can have trillions, making 'billions' the best general estimate.

The Sun is a medium-sized star (a yellow dwarf) and is far from being the largest star in the universe. It only appears much larger and brighter than other stars because it is incredibly close to Earth compared to the next nearest stars.

Shooting stars are meteors burning up as they enter Earth's atmosphere. This friction and burning typically occur in the mesosphere, which is dense enough to cause friction but high enough for meteors to first encounter significant resistance.

Distances in space are so vast that everyday units like miles or kilometers are too small to be practical. Astronomers use light-years, which is the distance light travels in one year (about 5.88 trillion miles).

Shooting stars, or meteors, burn up in the mesosphere as they enter Earth's atmosphere. The friction with the gas molecules in this layer creates enough heat to vaporize the meteors, making them visible.

A constellation is a recognizable pattern or group of stars in the night sky that forms an imaginary outline or picture. These stars are often far apart in space but appear close together when viewed from Earth.

Polaris, also known as the North Star, is positioned almost directly above Earth's geographic North Pole. Because of this alignment, it appears nearly stationary in the night sky while other stars seem to rotate around it.

The IAU definition of a planet requires that the object orbits a star, has sufficient mass for a round shape, and has cleared its orbital neighborhood of other debris.

The Solar System consists of the Sun, the eight planets, their moons, and various smaller bodies like asteroids and comets that are gravitationally bound to the Sun.

Volume is the measure of the amount of three-dimensional space an object occupies.

The Milky Way galaxy is part of the Local Group, which is itself a member of the Virgo Supercluster.