Types of Stars in the Universe

Classification of Stars

• Stars can be classified into 7 groups based on their properties, or spectral attributes, including size, color, temperature, and stage in their life cycle.

Spectral Classification

• O-class stars:
  • Hottest stars with surface temperatures > 28,000K
  • Blue in color, very bright, and short-lived
• B-class stars:
  • Surface temperatures between 20,000-30,000K
  • Blue-white in color, very bright, and short-lived
• A-class stars:
  • Surface temperatures between 10,000-20,000K
  • White in color, relatively young, and rare in the universe
• F-class stars:
  • Surface temperatures between 7,000-10,000K
  • Whitish-yellow in color, relatively bright, and in the middle of their life cycle
• G-class stars:
  • Surface temperatures between 6,000-7,000K
  • Yellow in color, large, and with an average brightness
  • Our sun is a G-class star
• K-class stars:
  • Surface temperatures < 5,000-6,000K
  • Orange in color, relatively old, and in the later stages of their life cycle
• M-class stars:
  • Coolest stars with surface temperatures < 5,000K
  • Red in color, large, and old, with a short life cycle

Classification by Size

• Supergiant stars:
  • Largest stars with immense mass
  • Can fit over 1 million Earths
  • Short-lived, with lifespans of 10-50 million years
• Giant stars:
  • Not as large as supergiants, but still huge
  • Similar to supergiants in life span and size
  • K and M-class stars with temperatures between 3,500-5,000K
• Main-sequence white dwarf stars:
  • Small in size, but with high temperatures > 100,000K
  • Very bright, with a high density and strong gravitational pull
• Brown dwarf stars:
  • Similar in size to Jupiter, but with a higher mass
  • Create their own light, but do not shine like other stars
  • Less luminous than other stars, with a long lifespan

Classification by Life Cycle

• Protostar:
  • First stage in a star's life cycle
  • Gravity pulls in gas and dust, forming a large spherical ball
  • Takes approximately 100,000 years to reach the next stage
• T Tauri star:
  • Second stage in a star's life cycle
  • Gets energy from gravitational pressure
  • Takes 100 million years to reach the next stage
• Main-sequence star:
  • Third stage in a star's life cycle
  • Begins nuclear fusion, with a long lifespan in equilibrium
  • Lifespan depends on mass, with more massive stars burning through energy faster
• Red giant star:
  • Fourth stage in a star's life cycle
  • Hydrogen core burns out, and the star grows larger
  • Can be 100 times bigger than its main-sequence stage

Learn about different types of stars in the universe including supergiants, giant stars, and main-sequence stars. Discover their characteristics, temperatures, and lifespans.