Astronomy Quiz-9th

Galaxy

A large system of stars, gas, dust, and dark matter bound together by gravity. Galaxies can contain billions of stars and may be spiral, elliptical, or irregular in shape.

Black Hole

A region in space where the gravitational pull is so strong that nothing, not even light, can escape from it. Black holes are formed when massive stars collapse under their own gravity at the end of their life cycle.

White Dwarf

A small, dense star that is the remnants of a low to medium mass star after it has completed its nuclear fusion stages. White dwarfs are usually hot and gradually cool over time.

Red Giant

A late stage in the life cycle of a star, characterized by expansion and cooling as it exhausts its nuclear fuel. Red giants are typically larger and brighter than the main sequence stars from which they evolve.

Super Red Giant

An even larger and more luminous phase of a red giant star, formed from massive stars that extend the process of hydrogen burning before going through more complex fusion processes. Super red giants ultimately evolve into supernovae, marking the end of their life cycle.

Planetary Nebula

A ring-shaped nebula formed by the explosion of a dying star, where outer layers are expelled during the red giant phase. It often surrounds a white dwarf at the center.

Super Nova

A cataclysmic and luminous stellar explosion that occurs during the final stages of a massive star's life or when a white dwarf is triggered into runaway nuclear fusion. During this event, a star can briefly outshine an entire galaxy, radiating as much energy as the Sun is expected to emit over its entire life span.

Neutron Star

A incredibly dense celestial object composed almost entirely of neutrons, resulting from the gravitational collapse of a massive star after a supernova.

Main Sequence Star

A star in the stable stage of its life cycle, characterized by the nuclear fusion of hydrogen (HH) into helium (HeHe) in its core. During this phase, the star achieves hydrostatic equilibrium, where inward gravitational pressure is balanced by outward thermal pressure.

Big Bang

The leading physical theory that explains the origin of the universe, suggesting it began as a near-infinite density and temperature approximately 13.813.8 billion years ago and has been expanding ever since.

Doppler Shift

The change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. In astronomy, it is used to measure the radial velocity of stars and galaxies.

Red Shift

A specific type of Doppler shift where the light from an object moving away from the observer is shifted toward longer, redder wavelengths. This phenomenon is a key piece of evidence for the expansion of the universe.

Lunar Eclipse

An astronomical event that occurs when the Earth passes between the Sun and the Moon, casting its shadow (the umbra) on the Moon. This can only happen during the full moon phase.

Solar Eclipse

An event that occurs when the Moon passes between the Sun and the Earth, partially or fully blocking the Sun's light from reaching Earth. This can only occur during the new moon phase.

Inner Planets

The four terrestrial planets closest to the Sun: MercuryMercury, VenusVenus, EarthEarth, and MarsMars. They are characterized by solid, rocky surfaces and relatively small sizes compared to the outer planets.

Outer Planets

The four planets furthest from the Sun: JupiterJupiter, SaturnSaturn, UranusUranus, and NeptuneNeptune. These are large planets primarily composed of gases and ices, often possessing many moons and ring systems.