Cosmic Alchemists: How Elements Form in Stars Quiz

If the early universe was extremely hot and dense but expanded rapidly, then only the lightest nuclei had time to form before temperatures dropped below the fusion threshold; therefore, the universe was left with approximately 75% hydrogen and 25% helium.

If core temperatures exceed approximately 17-20 million Kelvin, then the CNO cycle becomes the more efficient and dominant pathway for hydrogen fusion; therefore, the p-p chain is only dominant in cooler stars like the Sun.

If a star has exhausted its core hydrogen and the core contracts to reach 100 million Kelvin, then helium nuclei can overcome their mutual repulsion to fuse; if three helium nuclei are required to form carbon, the process is the triple-alpha process.

If a catalyst is a substance that facilitates a reaction without being consumed by the net process, and if the CNO cycle involves the transformation of hydrogen into helium using carbon, nitrogen, and oxygen nuclei as intermediaries, then those three elements are the catalysts.

If Lithium, Beryllium, and Boron are highly susceptible to destruction at the temperatures found in stellar interiors, and if they are not major products of common stellar fusion chains, then their cosmic abundance will remain significantly lower than elements like Carbon.

If an element has the highest binding energy per nucleon, then neither fusion nor fission of that nucleus will release energy; if the process requires an energy input (endothermic), then the star cannot use it to generate the outward pressure needed to resist gravity.

If the s-process requires a relatively low flux of neutrons and a long timeframe to allow for beta decay between captures, and if the helium-burning shells of AGB stars provide these exact conditions, then the s-process is characteristic of these evolved stars.

If nuclei with even numbers of protons are more stable due to pairing effects and if the alpha process adds two protons (helium nuclei) at a time, then even-numbered elements will naturally be more abundant.

If alpha elements are produced by the capture of alpha particles (helium nuclei with 2 protons), and if these elements have atomic numbers (Z) that are multiples of 2 starting from carbon, then Neon, Magnesium, Silicon, and Calcium qualify while Fluorine does not.

If fusion beyond iron is endothermic and cannot occur in a stable star, and if creating heavy elements requires a rapid, intense flux of neutrons (r-process), then these elements must be formed in violent events like supernovae or neutron star mergers.

If astronomers classify all matter in the universe into Hydrogen, Helium, and everything else, then any element with an atomic number greater than 2 is collectively referred to as a "metal" regardless of its chemical properties.

If a massive star has a carbon core that contracts and heats up, it begins to capture alpha particles (helium nuclei); if this sequence continues by adding 4He to existing nuclei to create O, Ne, Mg, and Si, it is known as the Alpha Ladder.

If stars inherit their composition from the interstellar medium, and if the early universe had not yet been enriched by many generations of stellar deaths, then stars formed during that era (Population II) will have a lower concentration of heavy elements.

If Lithium, Beryllium, and Boron are destroyed in stars, then they must be created elsewhere; if cosmic rays provide enough energy to shatter heavier nuclei in interstellar space, then this "spallation" process explains their existence.

If silicon burning proceeds through a complex series of rearrangements and alpha captures, and if the sequence terminates at the most tightly bound nucleus which is Iron-56, then Iron is the final product that accumulates.

If the r-process requires nuclei to capture many neutrons before they have time to beta-decay, then it requires an extremely high density of neutrons and an environment that provides this flux instantly, such as a supernova or merger.

If the Sun is a Population I star formed from a gas cloud previously enriched by older supernovae, then it will contain heavy elements like Iron that were present in the cloud at the time of its formation.

If iron fusion is endothermic and consumes energy, then the temperature and pressure in the core will drop suddenly; if the outward pressure fails to balance gravity, the core must collapse catastrophically.

If oxygen nuclei (Z=8) fuse at approximately 1.5 billion Kelvin, then the common resulting products include Silicon (Z=14), Phosphorus (Z=15), Sulfur (Z=16), and Magnesium (Z=12).

If light from a star's interior passes through its cooler outer atmosphere, and if specific elements in that atmosphere absorb specific wavelengths of light, then the resulting dark absorption lines indicate which elements are present.