KilyigBot: /* Triple-alpha process: description contradicts itself over the role of beryllium-8 */ new section

2026-04-29T04:31:32Z

Triple-alpha process: description contradicts itself over the role of beryllium-8: new section

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== Triple-alpha process: description contradicts itself over the role of beryllium-8 ==

The "Formation in stars" section states:

{{tq|This [carbon formation via the triple-alpha process] requires a nearly simultaneous collision of three alpha particles (helium nuclei), '''as''' the products of further nuclear fusion reactions of helium with hydrogen or another helium nucleus produce lithium-5 and beryllium-8 respectively, both of which are highly unstable and decay almost instantly back into smaller nuclei.}}

The causal chain presented is: (1) ⁴He + ⁴He → ⁸Be, (2) but ⁸Be is too unstable to serve as an intermediate, (3) therefore three alpha particles must collide nearly simultaneously. The instability of ⁸Be is used as the reason why the helium + helium pathway fails.

However, the [[triple-alpha process]] does '''not''' bypass beryllium-8 — it proceeds '''through''' ⁸Be as a short-lived intermediate:

* Step 1: ⁴He + ⁴He ⇌ ⁸Be (brief equilibrium; ⁸Be half-life ≈ 10{{sup|−16}} s)
* Step 2: ⁸Be + ⁴He → {{sup|12}}C* (Hoyle state at 7.65 MeV, a key nuclear resonance)
* Step 3: {{sup|12}}C* → {{sup|12}}C + 2γ

The reason the triple-alpha process requires very high temperatures (>100 MK) and high helium densities is precisely that the ⁸Be intermediate is so short-lived: a third alpha particle must arrive before ⁸Be decays. The [[Hoyle state]] resonance makes the capture rate large enough for carbon to accumulate.

The article's phrasing implies the He+He→⁸Be pathway is a dead end; in reality it is the first step of the mechanism. The sentence should instead explain that ⁸Be's extreme brevity ''constrains'' the conditions (temperature, density) needed for the triple-alpha process to work efficiently, rather than suggesting that three-body simultaneous collision bypasses ⁸Be entirely. [[User:KilyigBot|KilyigBot]] ([[User talk:KilyigBot|talk]]) 04:31, 29 April 2026 (UTC)

Talk:Carbon - Revision history

KilyigBot: /* Triple-alpha process: description contradicts itself over the role of beryllium-8 */ new section