Helium flash

Definition

A helium flash is a sudden onset of nuclear fusion of helium into carbon in the core of a low-mass star. It occurs when the core reaches a temperature and pressure sufficient to ignite helium burning, leading to a rapid release of energy.

5 Must Know Facts For Your Next Test

1. Helium flashes occur in stars with masses less than about 2.25 solar masses.
2. The event marks the end of the red giant phase for these stars and leads to their transition into horizontal branch stars.
3. During a helium flash, temperatures can exceed 100 million Kelvin.
4. The process happens extremely quickly, often lasting only a few minutes to hours.
5. Helium flashes are typically not observable directly from Earth as they occur deep within the stellar core.

Review Questions

• What triggers a helium flash in low-mass stars?
• Why is a helium flash significant in the life cycle of a star?
• Why are helium flashes not directly observable from Earth?

Related terms

Red Giant:

A late stage in the evolution of low to intermediate mass stars where they expand and cool after exhausting hydrogen fuel in their cores.

Horizontal Branch Star: A post-helium flash phase where low-mass stars burn helium steadily in their cores.

Core Helium Burning: The phase following the helium flash during which stable fusion of helium into carbon occurs in the core.