Observable Characteristics and Properties of Stars

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.