Types of Stars

Stars are categorized by their temperature, color, mass, and life stage. Here are the main types of stars:

1. Spectral Types (O–M Classification)

Stars are grouped by surface temperature and color using the Morgan–Keenan (MK) system, from hottest to coolest:

• O-type: Blue, extremely hot (>30,000 K), very rare, short-lived (e.g., Zeta Puppis)

• B-type: Blue-white, hot (10,000–30,000 K), luminous (e.g., Rigel)

• A-type: White, 7,500–10,000 K (e.g., Sirius)

• F-type: Yellow-white, 6,000–7,500 K (e.g., Procyon)

• G-type: Yellow, 5,200–6,000 K (e.g., our Sun, G2V)

• K-type: Orange, 3,700–5,200 K (e.g., Arcturus)

• M-type: Red, <3,700 K, most common (e.g., Proxima Centauri)

2. By Size and Brightness

These categories apply to different phases and masses:

• Main Sequence Stars: Like the Sun, fuse hydrogen in their cores.

• Giants: Stars that have expanded late in life, cooler but very large.

• Supergiants: Massive stars, extremely bright, often end as supernovae.

• White Dwarfs: Hot, dense remnants of stars like the Sun.

• Neutron Stars: Ultra-dense cores left after supernovae; often pulsars.

• Black Holes: Collapsed remnants of very massive stars.

3. Special Types

• Brown Dwarfs: "Failed stars" too small to sustain hydrogen fusion.

• Variable Stars: Change brightness due to internal or external factors (e.g., Cepheid variables).

• Binary and Multiple Star Systems: Stars that orbit a common center of mass.