When thinking about the hottest things on Earth, a few contenders likely come to mind: blazing deserts, erupting volcanoes, scorching wildfires. But what is definitively the hottest naturally occurring phenomenon on our planet? Let’s examine some record-breaking extremely hot places and objects to find out.
Lava
Lava is molten rock that erupts from volcanoes at temperatures of 700°C to 1,200°C (1,300°F to 2,200°F). This makes lava the hottest natural substance on Earth’s surface. The temperature varies based on the chemical composition of the lava and the volcano it emerges from. For example, lava from the Kilauea volcano in Hawaii reaches temperatures around 1,170°C (2,140°F).
When lava first erupts from a volcano, it can be even hotter. At the point of eruption within a volcano, lava can reach 1,600°C (2,912°F). But it quickly loses heat as it flows and spreads, cooling to the lower temperatures typical of lava.
Molten Iron
At Earth’s core lies molten iron and nickel, with temperatures estimated between 4,000-5,700°C (7,232-10,292°F). This liquid outer core surrounds Earth’s solid metal inner core and enables our planet’s magnetic field. The crushing pressures of Earth’s depth keep this iron fluid molten.
While these extreme temperatures of Earth’s core aren’t directly observable, scientists calculate these values based on the melting point of iron at low pressures and analyses of seismic waves traveling through the inner core.
Boltzmann Brain
A Boltzmann brain is a hypothetical self-aware entity that arises due to random fluctuations out of a state of chaos. The idea is that if given enough time, even a system in thermodynamic equilibrium—with completely random particle movements—could randomly form a conscious, self-aware entity.
This randomly fluctuating “brain” could theoretically achieve blazing temperatures on the order of 1010 K or more. However, Boltzmann brains are considered more of a thought experiment than a real physical phenomenon.
Relativistic Jets
Relativistic jets are extremely powerful beams of plasma and particles ejected from black holes at close to the speed of light. They reach incredible temperatures of over 1012 K—that’s 10 trillion degrees Celsius!
These jets form perpendicular to the accretion disk around the black hole. Gas spinning around the accretion disk becomes heated and compressed, shooting plasma particles outward in focused jets. This produces some of the hottest sustained phenomenon in the known universe.
Solar Corona
The sun’s surface only reaches about 5,500°C. But the solar corona, the aura of plasma surrounding the sun, hits staggering temperatures of 1,000,000°C to 5,000,000°C. That’s up to 9,000 times hotter than the sun’s surface!
What makes the solar corona burn so blisteringly hot? Scientists don’t yet have a definitive answer but suggest complex magnetic fields restructure and heat plasma around the sun.
Table of Hot Solar System Objects
| Object | Temperature (Celsius) |
|---|---|
| Sun’s core | 15,000,000°C |
| Sun’s surface | 5,500°C |
| Solar corona | 1,000,000°C – 5,000,000°C |
| Lightning | 30,000°C |
| Venus surface | 470°C |
| Mercury surface | 430°C |
| Lava | 700°C – 1,200°C |
Stellar Interiors
The centers of stars reach scorching temperatures hotter than any surface phenomenon on a planet. Our own sun’s core burns at around 15,000,000°C. At these extreme interior temperatures, nuclear fusion converts hydrogen into helium and releases enormous energy.
As stars age and cool, their cores can collapse even further, driving temperatures up. For example, a neutron star—the condensed remnant of a large star after supernova—can reach core temperatures over 100 trillion degrees Celsius.
Shock Diamonds
When supersonic jets and rockets fly faster than the speed of sound, shock diamonds may form in the exhaust plumes. As engine exhaust gases interact with surrounding air, shock waves compress the gases into hot diamond-like patterns.
The gas heats up significantly within these shock diamond regions, reaching temperatures of 3,000-4,000°C. This makes shock diamonds one of the hottest phenomena created by human technology and engineering.
Fusion Reactions
Nuclear fusion, the reaction that powers stars, reaches insane temperatures of over 150,000,000°C. Hydrogen atoms fuse into heavier helium within stellar cores. The sun converts over 600 million tons of hydrogen into helium every second!
Scientists are also working to harness the power of fusion here on Earth. Experimental fusion reactors have achieved temperatures of 100,000,000°C. But so far, no reactor has been able to produce a net energy gain for electricity generation.
Table of Experimental Fusion Reactors
| Reactor | Temperature | Location |
|---|---|---|
| Joint European Torus (JET) | 150,000,000°C | United Kingdom |
| International Thermonuclear Experimental Reactor (ITER) | 150,000,000°C | France (under construction) |
| National Ignition Facility (NIF) | 100,000,000°C | United States |
| Wendelstein 7-X | 100,000,000°C | Germany |
| Experimental Advanced Superconducting Tokamak (EAST) | 50,000,000°C | China |
Lightning
A lightning bolt can heat the air it passes through to temperatures 5 times hotter than the surface of the sun. The air channels in a lightning discharge reach 30,000°C. This causes the air to rapidly expand and contract, producing booming thunder.
Lightning occurs when charge builds up between storm clouds and the ground. The rapid discharge heats up the air momentarily to scorching temperatures hotter than any human-made source.
Deserts
The world’s hottest deserts can reach blistering surface temperatures up to 70°C. Death Valley holds the record for the hottest air temperature ever recorded at 56.7°C. Meanwhile, the Lut Desert in Iran has measured earth surface temperatures over 70°C using satellites.
Why do deserts get so hot? The lack of water means there is less evaporation that would normally have a cooling effect. Dry ground heats up rapidly under constant, intense sunlight.
Table of Earth’s Hottest Deserts
| Desert | Record Temperature | Location |
|---|---|---|
| Dasht-e Lut | 70.7°C ground temperature | Iran |
| Death Valley | 56.7°C air temperature | United States |
| Sahara | 58°C ground temperature | Africa |
| Sonoran | 57.2°C air temperature | United States/Mexico |
| Mojave | 56.7°C air temperature | United States |
Lichens
Extreme heat-loving microbes called thermophiles inhabit hot springs and geothermal vents. But the hottest place these tiny creatures can thrive reaches scorching temperatures of 122°C. At thermal vents this hot, thermophilic lichens from species like Rhizocarpon manage to eke out an existence.
These hardy lichens absorb heat and obtain nutrients from the venting steam and gases. Their heat-resistant cells allow them to survive at temperatures well above the boiling point of water.
Dalton Minimum Temperatures
While not a permanent place or object, the Dalton Minimum refers to an historic period of low solar activity between 1790-1830. Sunspots became exceedingly rare during this decades-long solar minimum. Accordingly, average global temperatures on Earth dropped substantially.
Scientists deduce that temperature averages around much of the world declined by 1-2°C during the Dalton Minimum compared to periods of higher sunspot prevalence. Tree ring data and other annual growth records provide evidence of the temperature shifts.
Conclusion
From scorching deserts to smoldering lava, Earth harbors some impressively hot natural phenomena. But even these extreme temperatures can’t compare to the mind-boggling heat inside stars or experimental fusion reactions. Out of all the record-breaking blazing places and objects across the cosmos, nuclear fusion at a star’s core likely takes the prize for the hottest sustained temperature in the observable universe.