Untitled Flashcards Set

Spiral Galaxy

A type of galaxy with a flat, rotating disk that contains stars, gas, and dust, along with a central bulge and spiral arms.

Elliptical Galaxy

A type of galaxy that ranges from nearly spherical to elongated shapes and contains very little gas and dust, dominated by older, redder stars.

Irregular Galaxy

A type of galaxy with no definite shape or structure, often resulting from gravitational interactions or collisions.

Hubble Tuning Fork Diagram

A classification system that categorizes galaxies into spirals, barred spirals, ellipticals, and irregulars.

Milky Way Galaxy

A barred spiral galaxy containing 100-400 billion stars, about 100,000 light-years in diameter.

Redshift

The phenomenon where light from a galaxy shifts to longer wavelengths as it moves away, indicating the expanding universe.

Blueshift

Occurs when a galaxy moves closer, causing its light to shift to shorter wavelengths.

Hubble’s Law

The law stating that the farther away a galaxy is, the faster it is moving away from us, expressed as Velocity = H₀ × Distance.

Edwin Hubble

An astronomer who discovered that 'nebulae' were other galaxies and provided evidence for an expanding universe.

Cosmic Microwave Background (CMB)

Faint radiation left over from the Big Bang, uniform across the sky, supporting the hot, dense early universe hypothesis.

Dark Matter

Invisible matter that does not emit light or energy, detected through its gravitational effects and helps explain galaxy rotation curves.

Dark Energy

A mysterious force causing the accelerated expansion of the universe, making up about 68% of it.

Age of the Universe

Estimated to be approximately 13.8 billion years, determined using Hubble's Law and cosmic background radiation data.

Dynamic Universe

The concept that the universe evolves over time, with galaxies forming, merging, and changing.

Gravity’s Role

The force that pulls gas and dust together to form stars and galaxies, determining shapes and motion.