Astronomy and Cosmology

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.

According to Kepler's third law of planetary motion, planets closer to the Sun have shorter orbital paths and experience stronger gravitational pull, resulting in faster orbital speeds and shorter orbital periods. Mercury is the closest planet to the Sun, so its year is much shorter than Earth's.

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.

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

When a star exhausts its hydrogen fuel, the core contracts and heats up, causing the outer layers to expand and cool, transforming the star into a giant or supergiant.

Stars spend the majority of their lives in the main-sequence stage, during which they fuse hydrogen into helium in their cores. Protostars are still forming, while giants and white dwarfs are later stages of stellar evolution.

A sun-like star begins as a protostar, enters the main-sequence, expands into a giant or supergiant, and finally collapses into a white dwarf. This sequence follows the standard model of stellar evolution for stars of this mass.

The core of a star is characterized by extreme heat, high pressure, and fast-moving atoms undergoing fusion. Blueish-yellow is a description of surface temperature or color, not a physical property of the core itself.

The term 'planet' comes from the Greek word for 'wanderer'. Ancient observers noticed that these objects moved relative to the background of fixed stars.

Shooting stars are not actual stars; they are meteors, which are small particles of dust or rock that burn up upon entering Earth's atmosphere.

Hairy stars is an archaic term for comets, referring to the appearance of their tails as they approach the Sun.