Life Cycle of a Star and Galaxy Classification

Star

A massive celestial body undergoing nuclear fusion.

Nebula

Cloud of gas and dust forming stars.

Gravity

Force pulling matter together in space.

Protostar

Early stage of star formation from collapsing nebula.

Nuclear Fusion

Process fusing atomic nuclei, generating star energy.

Main Sequence Star

Stable phase of a star's life cycle.

Red Giant Star

Star expanding after hydrogen fuel depletion.

Red Super Giant

Massive star in late life stage before supernova.

Planetary Nebula

Cloud of gas from dying medium-sized stars.

White Dwarf

Dense remnant of a low or medium mass star.

Black Dwarf

Cold, inactive remnant of a white dwarf.

Supernova

Explosive death of a massive star.

Neutron Star

Remnant core of a supernova, extremely dense.

Pulsar

Neutron star emitting radio waves in pulses.

Black Hole

Region with gravity so strong that light cannot escape.

Star Mass

Amount of matter determining a star's life cycle.

Life Cycle

Stages a star undergoes from formation to death.

Hydrogen Fuel

Primary fuel for nuclear fusion in stars.

Core Temperature

Heat at the center of a star during fusion.

Carbon Fusion

Process forming carbon from helium in stars.

Iron Absorption

Iron atoms absorbing energy, halting fusion.

Temperature of Supernova

Can reach up to 1 billion degrees Celsius.

Massive Star

Star with significantly larger mass than the sun.

Medium-sized Star

Star with mass similar to or slightly larger than the sun.

Life Span

Duration a star exists before dying.

Star Formation

Process involving gravity and nuclear fusion.

Galaxy

A huge collection of gas, dust, and billions of stars that are being held together by gravity.

Light-year

A unit of length used to express astronomical distances, equivalent to about 9.46 trillion km, defined as the distance that light travels in vacuum in one Earth year.

Parsec

A unit of distance equal to 3.26 light years.

Satellite Galaxies

Less massive galaxies that orbit a regular galaxy and have their own collection of stars.

Local Group

A small cluster of gravitationally bound galaxies that includes the Milky Way.

Local Supercluster

An irregular group of clusters of galaxies, between 100 and 200 million light years in diameter.

Spiral Galaxy

A rotating disk of stars and dust with a dense bulge in the center and several arms spiraling out, appearing like a pinwheel.

Elliptical Galaxy

A galaxy with a shape that varies from nearly circular to very elongated, containing little gas and dust, and older stars.

Irregular Galaxy

A galaxy that is neither disk-like nor elliptical, lacking a regular shape and containing lots of bright young stars.

Milky Way

Our home galaxy, an example of a spiral galaxy with components including a bulge, disc, and stellar halo.

Bulge

A spherical structure found in the center of a galaxy, mostly containing older stars.

Disc

A flattened region surrounding the bulge in a galaxy, made up of dust, gas, and young stars.

Stellar Halo

A loose, spherical structure located around the bulge and some of the disc of a galaxy, containing old clusters of stars.

Sagittarius A

A supermassive black hole at the center of the Milky Way with a mass of about 4 million times that of our Sun.

Globular Clusters

Old clusters of stars found in the stellar halo of a galaxy.

Supercomputers

Powerful computers used by scientists to simulate galaxy formation and study the early universe.

Dwarf Galaxies

Galaxies containing as few as 100 million stars.

Giant Galaxies

Galaxies with more than a trillion stars.

Orion's Arm

The location of the Sun, about 8 kpc from the center of the Milky Way.

Large Magellanic Cloud

The largest satellite galaxy to the Milky Way, easily spotted with the naked eye from the Southern Hemisphere.

Small Magellanic Cloud

A smaller satellite galaxy to the Milky Way, also visible from the Southern Hemisphere.