Thermite and Sunspots
- A Temperature That Should Not Be Ignored
- What Is a Sunspot, and How Cold Does It Get?
- What Is Thermite, and Why Does Its Temperature Matter?
- Iron, Nickel, and Silicon: The Dominant Elements
- Boiling and Evaporation Points as Stability Windows
- A Surface Full of Oxides and Halides
A Temperature That Should Not Be Ignored
When a sunspot reaches its coldest point, something remarkable happens. The temperature lands right in the middle of a range that chemists know very well — the range where some of the most powerful fire-based reactions on Earth take place. That overlap is not a coincidence. It might be telling us something important about what the Sun is actually made of.
What Is a Sunspot, and How Cold Does It Get?
Sunspots are dark patches that appear on the surface of the Sun. They look dark because they are cooler than the blazing surface around them. The average sunspot is still incredibly hot — around 7,000 to 8,000 degrees Fahrenheit (roughly 3,900 to 4,400 degrees Celsius). But the very darkest, coldest centers of the largest sunspots — a region called the umbra — have been measured as low as approximately 3,500 Kelvin, which is about 5,840°F or 3,227°C.
What is a Kelvin? Scientists measure extreme temperatures in Kelvin (K) instead of Fahrenheit or Celsius. Zero Kelvin is absolute zero — the coldest anything can possibly be. To convert Kelvin to Celsius, subtract 273. So 3,500 K is about 3,227°C, or roughly 5,840°F. It is still extraordinarily hot by everyday standards, but in solar terms it is the coolest observable point on the Sun’s surface.
In the Liquid-Star Model, this 3,500 K minimum is not just a curiosity. It is treated as a boundary marker — the point where the condensed, liquid-metallic surface of the Sun becomes briefly visible through a gap in the overlying plasma. In other words, sunspot floors may be giving us a direct temperature reading of the actual surface beneath the Sun’s glowing atmosphere.
What Is Thermite, and Why Does Its Temperature Matter?
Thermite is a mixture of iron oxide (rust) and aluminum powder. When it is ignited, it produces one of the most intensely hot chemical reactions ever studied. The reaction is so energetic that it can melt through steel, which is why it has been used in welding, metalworking, and military applications.
Exothermic reaction: A chemical reaction that releases heat into its surroundings. “Exo” means outward, and “thermic” refers to heat. When thermite burns, it is not just glowing — it is releasing stored chemical energy in the form of intense heat and light. The temperature it reaches is a direct result of how much energy is packed into the bonds between its atoms.
Standard aluminum-iron oxide thermite burns at temperatures between roughly 2,500 K and 3,500 K (approximately 4,040°F to 5,840°F). The peak flame temperature of a classic thermite reaction sits right around 2,500 K to 3,000 K, though the molten iron it produces can remain near 3,000 K for a brief period. More advanced thermite mixtures — those using different oxides such as iron(III) oxide combined with magnesium or silicon — can push reaction temperatures higher, into the 3,000–3,500 K range.
Now look at those two numbers side by side: thermite peaks at up to 3,500 K, and the coldest sunspot floors bottom out at approximately 3,500 K. The ranges do not merely touch — they converge at exactly the same point.
🔥 The Overlap at a Glance
Coldest sunspot umbra: ~3,500 K | Thermite peak reaction temperature: ~2,500–3,500 K. These two independently measured values share the same upper boundary. In the Liquid-Star Model, that is not a coincidence — it is a chemical fingerprint.
Iron, Nickel, and Silicon: The Dominant Elements
The Liquid-Star Model proposes that the Sun’s outer surface is a molten mixture dominated by iron, nickel, and silicon — the same heavy metals found in Earth’s core and in stony-iron meteorites. At around 3,500 K, these elements are not just present. They are actively interacting with oxygen, and those interactions are deeply exothermic.
Iron (Fe)
Iron is the most important element in this picture. Iron boils at approximately 3,134 K under normal pressure. That means at 3,500 K, iron is not quietly sitting in the melt — it is right at or just past its boiling point. Iron vapor is rising off the surface and immediately reacting with any available oxygen to form iron oxide in an exothermic burst. This is essentially a natural thermite precursor reaction happening continuously at the sunspot boundary.
The stability range of liquid iron — between its melting point of about 1,811 K and its boiling point of 3,134 K — defines the window in which molten iron can exist as a calm liquid. Above 3,134 K, iron begins to evaporate. Near the sunspot floor temperature of 3,500 K, iron is actively transitioning from liquid to vapor, which releases additional energy and feeds the overlying plasma with iron ions. This is exactly what the Liquid-Star Model predicts: iron being continuously sputtered off the condensed surface into the atmosphere above.
Nickel (Ni)
Nickel behaves similarly. It melts at 1,728 K and boils at 3,186 K — almost identical to iron. At 3,500 K, nickel is also above its boiling point and evaporating into the plasma column. Nickel oxide (NiO) forms readily in the presence of oxygen and is itself a product of an exothermic reaction. The Ni II spectral lines (lines that show up when nickel loses electrons) are detected in the solar chromosphere, which is exactly where you would expect to find ionized nickel vapor rising from a hot metallic surface.
Silicon (Si)
Silicon adds a different dimension. It boils at a much higher temperature — around 3,538 K — which places it almost exactly at the sunspot floor temperature. This means silicon is sitting right at its boiling boundary at the coolest observable point on the Sun. Silicon that is in the liquid surface is on the verge of evaporating into gas.
When silicon reacts with oxygen, it forms silicon dioxide (SiO&sub2;), also known as silica, in an extremely exothermic reaction releasing around 911 kilojoules per mole. Silicon monoxide (SiO) is also produced as an intermediate step and has actually been detected in the solar spectrum as a molecular emission band in the ultraviolet — a direct observational clue that silicon oxidation is happening at or just above the surface.
Boiling and Evaporation Points as Stability Windows
One of the most useful concepts for understanding the solar surface chemistry is the idea of a stability range — the temperature window between when a substance melts and when it boils. Within that window, a material exists as a stable liquid. Below the melting point, it is a solid. Above the boiling point, it evaporates into gas or vapor.
Evaporation and boiling: Evaporation happens gradually at a liquid’s surface when some molecules gain enough energy to escape into the air. Boiling is when the entire liquid reaches the energy needed for molecules throughout the fluid to turn to gas all at once. Both processes carry molecules away from the liquid surface into the atmosphere above.
At the sunspot floor temperature of 3,500 K, different elements are at very different points in their own stability ranges. Iron and nickel are above their boiling points and evaporating. Silicon is right at its boiling point. Magnesium (boiling point ~1,363 K) is far above its boiling point and has long since vaporized into the plasma. Calcium (boiling point ~1,757 K) is similarly already in vapor form at these temperatures.
What this means physically is that the sunspot floor — the coolest visible region of the Sun — is not a quiet, stable place. It is a boundary zone where the heaviest, highest-boiling elements are just barely holding on as liquid, while lighter elements have already evaporated upward. This creates a natural chemical sorting process: the surface retains the densest metals while continuously shedding lighter ones into the atmosphere as ions and vapor.
A Surface Full of Oxides and Halides
A molten metallic surface at 3,500 K exposed to oxygen, sulfur, and other reactive species would not remain a pure metal for long. The surface of the Liquid-Star Model’s solar outer core is expected to be rich in a wide variety of compounds — many of which have direct parallels in volcanic lava and in meteorite chemistry.
|Compound|Formula|Type|Formation Reaction|Relevance| ||| Based on the Liquid-Star solar model synthesizing the work of Prof. Pierre-Marie Robitaille, Dr. Oliver Manuel, and the Birkeland / Electric Universe plasma framework. Temperature data sourced from standard spectroscopic sunspot measurements and NIST thermochemical tables. The thermite reaction temperature range (2,500–3,500 K) is well-established in the peer-reviewed chemistry literature.
This article is part of the ongoing Liquid Star series exploring alternative perspectives on stellar structure, planetary formation, and energy generation._
About the Author
Adolfo Maldonado is an independent researcher and author developing the Liquid Star Model.
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