CAIE Physics I GCSE Topic 6: Space Physics - Vocabulary Flashcards

Vocabulary flashcards that cover all key definitions from CAIE Physics IGCSE Topic 6: Space Physics.

An invisible line around which an object rotates or spins.

Axis

Hemisphere

One of the two equal halves of Earth when it is divided horizontally—northern and southern.

Orbit

A repeating circular (or nearly circular) path taken by one body around another.

Orbital period

The time required for an object to complete one orbit.

Periodic

Describes a phenomenon that occurs at regular intervals.

Planet

A sphere of rock or gas that orbits a star and has enough gravity to pull in nearby objects.

Waxing

The phase during which the illuminated portion of the Moon’s visible surface is increasing.

Waning

The phase during which the illuminated portion of the Moon’s visible surface is decreasing.

Accretion

Growth by the gradual accumulation of matter.

Asteroid

A small rocky object, mainly found in the belt between Mars and Jupiter, that orbits the Sun.

Artificial Satellite

A human-made object placed into orbit around a planet, e.g., the International Space Station.

Comet

A body of dust and ice that orbits the Sun on a highly elliptical path that can extend beyond the Solar System.

Elliptical

Describes an oval-shaped orbit; some objects follow more elliptical paths than others.

Minor Planet

A body that orbits the Sun but lacks sufficient gravity to clear its orbital neighborhood.

Natural Satellite

A naturally occurring body that orbits a planet, such as a moon.

Solar System

A star and all the objects gravitationally bound to it; Solar Systems orbit within galaxies.

The Sun

The star at the center of our Solar System.

Electromagnetic spectrum

The full range of electromagnetic wavelengths or frequencies.

Infrared radiation

Radiation with wavelengths longer than visible red light and shorter than microwaves; perceived as heat.

Nuclear fusion

The process in which two light nuclei combine to form a single heavier nucleus.

Star

A massive ball of gas, primarily hydrogen and helium, held together by gravity.

Ultraviolet radiation

Radiation with wavelengths shorter than visible light but longer than X-rays; causes skin to darken.

Visible radiation

Electromagnetic waves with wavelengths between ultraviolet and infrared, detectable by the human eye.

Astronomical distance

The separation between celestial objects, commonly expressed in light-years (9.5 × 10¹⁵ m).

Galaxy

A vast collection of stars, each with its own Solar System; the Sun resides in the Milky Way galaxy.

Nebula

A massive cloud of gas and dust from which stars form.

Protostar

A collapsing cloud of gas and dust that is not yet hot enough to emit light like a star.

Stable star

A star in equilibrium where gravity balances the outward gas pressure from nuclear fusion (e.g., the Sun).

Big Bang Theory

The theory that the Universe began ~13.8 billion years ago from a hot, dense state and has been expanding since.

Cosmic microwave background radiation (CMBR)

Microwave radiation of specific frequency present throughout space, predicted by the Big Bang Theory.

The Hubble Constant

The ratio of a galaxy’s recessional speed to its distance from Earth.

Recede

To move farther away.

Redshift

The observed increase in wavelength of electromagnetic radiation emitted by an object moving away.

Universe

All of space, containing all galaxies and their Solar Systems.