Observable Characteristics and Properties of Stars

Basic Characteristics of Stars

Stars are gigantic, radiant spheres of plasma primarily composed of hydrogen and helium.
The apparent brightness of a star as seen from Earth is known as its magnitude. The closer a star is to us and the more luminous it is, the greater its magnitude.
Stars emit light in various colours, each indicating a specific temperature range.
The colour of a star changes through its lifetime, corresponding to changes in temperature.
The hottest stars appear blue, middle-temperature stars including our Sun appear yellow, and the coolest stars appear red.

Star Classification

Stars are classified according to the Hertzsprung-Russell (H-R) diagram, a graph that plots their temperature (or colour) against their absolute magnitude (or luminosity).
The main categories on the H-R diagram include main sequence stars, red giants, and white dwarfs.
Main sequence stars, like our Sun, are in the stage of their life where they are fusing hydrogen into helium in their cores.
Red giants are older stars in a later evolutionary stage, with cooler, outer layers that make them large and bright.
White dwarfs are the remnants of stars after they have exhausted their nuclear fuel, smaller and dimmer, but very hot.

Patterns of Star Movement

Stars exhibit regular patterns of movement in the night sky. This is due to the rotation of Earth on its axis.
The apparent path that stars take in the night sky is circular, moving from east to west. This is called the diurnal motion of stars.
Star positions also shift throughout the year due to Earth’s revolution around the Sun. This gives us different constellations in different seasons.

Star Distances

Astronomers measure vast stellar distances using a unit called the light year, the distance light travels in one Julian year.
Another method for gauging distances to nearby stars is parallax, the apparent shift in position of a nearby star, viewed from two different points.

Star Evolution

Stars evolve over billions of years, undergoing various stages such as nebula, protostar, main sequence star, red giant, and white dwarf.
Ultimately, a star’s mass will determine its fate: becoming a neutron star, a white dwarf, or a black hole.

Studying these key characteristics and properties of stars aids our understanding of the universe’s literal stars, and our own Sun’s past, present and future.