It is hypothesized that carbon and silicon could form the “backbone” of DNA. Using the figure below, which of the following scenarios might lead to a star system that has more silicon than carbon?

Question

BlackTom AI · Accepted Answer

To tackle this question, let's think about how elements like carbon and silicon get into the interstellar medium from generations of stars.
Option 1: 'It formed near low-mass stars, but no high-mass stars.' Low-mass stars do contribute carbon later in their lifetimes, but the absence of high-mass stars means fewer supernovae that synthesize and eject silicon; this would not strongly favor silicon over carbon. So this choice is unlikely.
Option 2: 'It formed in proximity to many high-mass stars, but few low-mass stars.' High-mass stars end their lives in core-collapse supernovae, producing and dispersing alpha-process elements like silicon (Si) along with oxygen and magnesium. If a forming system is enriched by many such explosions and has few low-mass stars contributing carbon-rich material, the environment would accumulate more silicon relative to carbon. This aligns with the hypothesis about silicon enrichment.
Option 3: 'It is a binary star system.' Merely being a binary doesn't dictate the chemical makeup of the surrounding nebula; without information about the masses of the progenitors or their nucleosynthetic contributions, this doesn't explain silicon dominance.
Option 4: 'It formed from “raw” material from the Big Bang.' Big Bang material is mostly hydrogen and helium with trace lithium; it lacks significant amounts of silicon or carbon, so this would not yield a silicon-rich system.
Option 5: 'It formed near a large number of exploding white dwarf stars.' Exploding white dwarfs (Type Ia supernovae) mainly produce iron-peak elements rather than silicon in large excess relative to carbon, so this would not preferentially boost silicon over carbon. Therefore, this choice is not the best explanation for a silicon-rich backbone.
Overall, the reasoning points to Option 2 as the scenario that would likely result in a star system with more silicon than carbon due to enrichment from high-mass star supernovae and relatively less carbon input from low-mass stars.

EESC1120.01|.02 Summer 2025 Our Home Amongst the Cosmos [Kruckenberg] Week 6 Quiz

It is hypothesized that carbon and silicon could form the “backbone” of DNA. Using the figure below, which of the following scenarios might lead to a star system that has more silicon than carbon?

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