Astronomy

The Sun's layers from inner to outer are: Core → Radiative Zone → Convective Zone → Photosphere (visible surface) → Chromosphere → Corona. The Corona is the outermost layer, visible as a pearly white crown during total solar eclipses. Photosphere (C) is the visible surface, Chromosphere (A) is the thin layer above it.

Venus rotates in the opposite direction to most other planets.

Perihelion (closest distance to Sun) occurs around January 3rd each year, when Earth is about 147 million km from the Sun. December 22nd (B) is the winter solstice (shortest day in Northern Hemisphere) but not the closest distance. June 21st (C) is the summer solstice and aphelion (farthest point).

Light year is the distance that light travels in vacuum in one year.

Mars is called the 'Red Planet' due to its reddish appearance caused by iron oxide (rust) on its surface. Jupiter (A) is the largest planet with bands, Saturn (B) is known for its rings, and Venus (D) appears white/yellow.

Tides are primarily caused by the Moon's gravitational pull, with the Sun's gravity also contributing (about 46% of Moon's effect). The combined gravitational forces of both Sun and Moon create spring tides (stronger) and neap tides (weaker). Gravitation on Earth (D) itself doesn't cause tides - it's the differential gravitational pull from celestial bodies.

Sunspots are cooler regions on the Sun's photosphere with temperatures around 3,900°C (7,000°F), compared to the surrounding photosphere at about 5,500°C (9,900°F). The temperature difference makes them appear darker. Options A (6000°C) and B (5000°C) are too hot, while C (1500°C) is too cold.

Phobos is the larger and inner of Mars' two natural satellites (moons), along with Deimos. It orbits very close to Mars, completing about three orbits per Martian day. Uranus (B) has 27 moons including Titania and Oberon, Saturn (C) has 83 moons including Titan, and Venus (D) has no moons.

Phobos and Deimos are the two natural satellites of Mars, discovered by Asaph Hall in 1877. They are named after the Greek mythological figures representing fear and dread, who accompanied Ares (Mars). Earth has one moon, Venus has none, and Saturn has 83 confirmed moons.

A white dwarf is a stellar remnant composed mainly of electron-degenerate matter - essentially the exposed core of a star that has exhausted its nuclear fuel. They are very dense but small in size (about Earth-sized) and slowly cool over billions of years. Constellations are star patterns, comets are icy bodies, and asteroids are rocky objects.

 September 23 is called autumnal equinox.

Their size varies from barely a kilometre to a few hundred kilometres.

Kepler