From 4,300 °C to -223 °C: The Most Extreme Planets Discovered by Science

Written by Jefferson Augusto

Published on 09/02/2026 at 16:14

Updated on 09/02/2026 at 16:15

KELT-9b é o planeta mais quente já identificado, com temperaturas superiores a 4.300 °C, mais altas que as de muitas estrelas.

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Astronomical Discoveries Reveal Worlds That Vaporize Metals, Freeze Atmospheres, and Have Survived Since the Dawn of Cosmos

Modern astronomy has been revealing a Universe that is far more extreme than previously thought.
With the advancement of telescopes and observation methods, scientists identify planets outside the Solar System that challenge known physical limits.

Furthermore, these discoveries expand the understanding of the formation and evolution of planetary systems.
At the same time, they show that the diversity of worlds is much greater than previously believed.

The information was originally published by the site The Conversation, based on data from NASA and international observatories.
Next, learn about some of the most extreme planets ever discovered, each representing an impressive record in science.

ARTICLE CONTINUES BELOW

The Hottest Planet Ever Recorded Exceeds 4,300 °C and Rivals Stars

Among all known extreme planets, KELT-9b ranks first when it comes to temperature.
This exoplanet orbits the star KELT-9 (HD 195689), which is 2.5 times more massive than the Sun.

Moreover, the star has a surface temperature close to 10,000 °C.
Due to its extreme proximity to it, KELT-9b reaches temperatures exceeding 4,300 °C during the day.

This value surpasses the temperature of many known stars.
It is only about 1,100 °C below the surface of the Sun, which registers 5,500 °C.

As a result, metals like iron and titanium vaporize in the planet’s atmosphere.
Therefore, KELT-9b behaves more like a cosmic furnace than a traditional planet.

From Almost Absolute Zero to the Largest Planet Ever Cataloged by NASA

On the opposite extreme, the exoplanet OGLE-2005-BLG-390Lb is the coldest ever identified.
Its temperature reaches –223 °C, just 50 degrees above absolute zero.

Although it has 5.5 times the mass of Earth, it orbits a low-energy red dwarf star.
As a result, almost all gases in its atmosphere have solidified on the surface.

Not surprisingly, researchers have nicknamed it “Hoth”, in reference to the icy planet from Star Wars.

Meanwhile, the largest known planet is DENIS-P J082303.1-491201 b.
It has 28.5 times the mass of Jupiter, according to NASA’s exoplanet archive.

This value is so high that scientists are debating whether it can still be classified as a planet.
Curiously, its host star is also a brown dwarf.

The Smallest Detected Planet and the Oldest Known in the Universe

The smallest exoplanet ever discovered is Kepler-37b.
It is only slightly larger than the Moon and smaller than Mercury.

Because it orbits very close to its star, the planet has high temperatures.
Thus, it cannot maintain liquid water on its surface.

The oldest known planet is PSR B1620-26 b.
It has an estimated age of 12.7 billion years.

This means it formed when the Universe was still young.
It’s worth noting that the total age of the cosmos is calculated at 13.8 billion years.

Additionally, the planet orbits a rare system composed of a pulsar and a white dwarf.
This configuration challenges traditional models of planetary survival.

Conclusion

Together, these planets demonstrate how extreme and unpredictable the Universe is.
Some burn like failed stars, while others freeze completely.

Moreover, there are worlds that have existed since almost the beginning of the cosmos.
Each discovery pushes the boundaries of scientific knowledge.

At the same time, these observations raise new questions about the origin of planets.

In the face of such extreme planets, how far do you think science can go in discovering new worlds?

From 4,300 °C to -223 °C: The Most Extreme Planets Discovered by Science

Astronomical Discoveries Reveal Worlds That Vaporize Metals, Freeze Atmospheres, and Have Survived Since the Dawn of Cosmos

The Hottest Planet Ever Recorded Exceeds 4,300 °C and Rivals Stars

From Almost Absolute Zero to the Largest Planet Ever Cataloged by NASA

The Smallest Detected Planet and the Oldest Known in the Universe

Conclusion

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From 4,300 °C to -223 °C: The Most Extreme Planets Discovered by Science

Astronomical Discoveries Reveal Worlds That Vaporize Metals, Freeze Atmospheres, and Have Survived Since the Dawn of Cosmos

The Hottest Planet Ever Recorded Exceeds 4,300 °C and Rivals Stars

From Almost Absolute Zero to the Largest Planet Ever Cataloged by NASA

The Smallest Detected Planet and the Oldest Known in the Universe

Conclusion

A Chinese factory in Guangdong is assembling a humanoid robot every 30 minutes while Tesla, Figure, and Boston Dynamics still struggle to deliver 10 thousand per year.

Seven world powers including the US, China, and Russia are spending €22 billion on a reactor in the south of France that aims to confine plasma at 150 million degrees Celsius, ten times the temperature of the Sun’s core, using a magnetic field capable of lifting an entire aircraft carrier.

Secret chamber sealed 4,500 years ago found in the Pyramid of Khufu, and Hawass announces its opening to the world in 2026

A public school student single-handedly created a machine capable of treating water for up to 50 people using only solar energy. It was awarded third place at one of the most important science fairs in the world.

China has begun the second phase of energy assistance to Cuba with a 120 MW solar generation plan, and the first result is a photovoltaic park with batteries that regulates voltage, controls frequency, and provides local autonomy to an island suffocated by chronic blackouts.

Germany installed vertical solar panels on a lake in Bavaria, and the result broke conventional logic: instead of producing energy at midday peak, the plant generates more early in the morning and in the evening, exactly when families turn on appliances and factories are in full swing.

While countries lose water in the heat and dispute land for energy, India places solar panels over irrigation canals to generate electricity, shade the water, and transform agricultural infrastructure into a clean power plant.

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