Note4Students
From UPSC perspective, the following things are important :
Prelims level: Iron Inside the Sun
Why in the News?
Recent findings have revealed that iron’s opacity inside the Sun may be much higher than previously predicted, challenging current solar models.
Iron Inside the Sun:
- Iron makes up approximately 0.14% of the Sun’s mass, which is significantly less than hydrogen (~74%) and helium (~24%).
- Despite its small percentage, iron plays a crucial role in the Sun’s opacity. In the Sun, opacity influences how energy moves from the core to the surface.
- The higher the opacity, the more energy is trapped, impacting the Sun’s temperature, density, and fusion rates.
Highlights of the New Study:
- A 2025 study published in Physical Review Letters revealed that iron’s opacity in the Sun’s interior is 30-400% higher than previously predicted by models.
- Researchers exposed a thin iron sample to X-rays and used spectrometers to measure the shadow cast by the sample.
- By analyzing how strongly the iron absorbed the radiation, they were able to infer the element’s opacity.
- Significance:
- This discovery has important implications for how solar models are constructed.
- By correcting the opacity of iron, models of the Sun’s temperature profile, fusion rates, and energy distribution may need to be revised.
- This will lead to a more accurate understanding of stellar behaviour and energy transfer.
Back2Basics: Composition of the Sun
- The Sun primarily comprises hydrogen and helium, but other elements such as oxygen, carbon, neon, and iron also play significant roles.
|
Element |
Composition by Mass (%) |
Key Role |
| Hydrogen (H) | 74% | The primary fuel for nuclear fusion in the Sun’s core. It undergoes fusion to form helium, releasing energy that powers the Sun. |
| Helium (He) | 24% | A byproduct of hydrogen fusion, helium helps maintain the Sun’s stability and supports continued fusion processes. |
| Oxygen (O) | ~0.8% | Oxygen contributes to the Sun’s opacity, assisting in the transport of energy within the star. It also plays a role in nucleosynthesis, where heavier elements are formed in the Sun’s core. |
| Carbon (C) | ~0.3% | Carbon is involved in nucleosynthesis and plays a significant role in determining the Sun’s opacity and energy transport mechanisms. |
| Neon (Ne) | ~0.2% | Neon is found in the Sun’s atmosphere and is involved in the absorption of radiation, affecting the Sun’s energy output and behavior. |
| Iron (Fe) | ~0.14% | Although small in mass, iron significantly impacts the Sun’s opacity, scattering and absorbing radiation, which influences energy transfer. Iron’s opacity affects the Sun’s temperature, density, and fusion rates. |
| [UPSC 2002] Which one of the following statements is correct with reference to our solar system?
(a) The Earth is the densest of all the planets in our solar system (b) The predominant element in the composition of Earth is silicon (c) The Sun contains 75 per cent of the mass of the solar system (d) The diameter of the Sun is 190 times that of the Earth |
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