How Cold Is It In Outer Space?

Have you ever looked up at the night sky, perhaps at the moon, and thought to yourself, I could fit that in my mouth.

How Cold Is It In Outer Space

If not, don’t get judgy. We’ve all wondered weird things about space.

Perhaps the least weird thing that we’ve all wondered about it, is just how cold is it in space?

How Cold Is Outer Space?

We know for certain that space must be cold. This is because of two reasons:

  1. Space is a complete vacuum.
  2. The second reason why we know that the universe is cold is simply because the laws of physics dictate that what goes up must come down. And when something comes down, it gets colder (this includes objects like stars, planets, asteroids, comets etc).

To determine just how cold it is out there, NASA has launched unmanned satellites to measure temperatures in our solar system.

Using these measurements, scientists have worked out a rough estimate of how cold the rest of the known universe is.

The best estimate of how cold space is, according to Scientific, is -270 degrees Celsius (-451 degrees Fahrenheit).

But a more scientific unit of measurement for temperatures this low is Kelvin, and outer space is roughly 2.7 Kelvin, which is just shy of absolute 0.

To put that in a bit of context, the coldest place on planet Earth is the East Antarctic plateau, which often plummets to -148 degrees Fahrenheit, which is more than three times warmer than the temperature of deep space.

But you’d be surprised to know that space isn’t cold everywhere. The universe is huge. Inevitably, some areas are a lot warmer than expected.

How Hot Is It In Outer Space?

How Hot Is It In Outer Space

Well, it turns out that the answer to that question depends on what part of space you are talking about.

Scientists have done studies into different types of space and have determined that there are four zones within the Universe where the temperature fluctuates between roughly below -200 degrees and almost 142 nonillion kelvins, which is a fancy measurement for a butt load of heat.

Hot Jupiters – A Hot Jupiter is a planet that orbits very close to its star, typically within 0.05 AU (1 million km) of the star.

The term was coined by astronomers in 1995 when they discovered 51 Pegasi b, which has an orbital period of only 3 days and completes one orbit every 1.5 years.

The temperature of a Hot Jupiter is much higher than Earth’s because it receives more energy from its parent star.

In addition to being huge, Hot Jupiters are also very hot.

They receive enough heat from their stars to be significantly hotter than other exoplanets.

One of these is WASP-12b, which is the hottest planet ever discovered and has a surface temperature of around 2200 degrees Celsius.

Super-Earths and Sub-Neptunian Planets – Super-Earths are larger than Earth These are bigger versions of Earth and orbit their parent star much closer than Jupiter does.

They also often experience more intense radiation due to being so close.

On such planets, the main source of warmth is radioactive decay caused by the elements Uranium, Thorium and Potassium.

According to the BBC, “Atoms of these elements become unstable inside the body, emitting particles that cause the surrounding material to radiate away the energy.”

So basically, if you were standing next to one of these distant worlds, you would feel very warm.

But if you were standing on top of it, you would be freezing.

Kuiper Belt Objects – Also called Trans Neptunian Objects, these are similar to regular Neptunes but further out, orbiting the sun outside Neptune’s orbit.

Like super-Earths, these bodies receive heat from radioactivity, but unlike super-Earths, Kuiper belt objects do not have any sort of molten core inside them.

So it isn’t possible for these planets to have internal radiative cooling systems.

Instead, as explained in Discovery News, “Most of them consist of icy rocks, boulders, pebbles and specks — and there’s nothing to absorb most of the sunlight that shines onto them,” says planetary scientist David Jewitt of the University of California, Los Angeles.

“That means it takes some time before they get too hot.”

However, in the summertime, the Sun’s rays can be strong enough to melt some of this ice.

Hence, the reason why some of the Kuiper belt bodies are known to be geologically active.

This activity includes water erosion, plate tectonics and even meteorite impacts.

Interstellar Space – Interstellar space refers to all that space that we see between the stars, planets, galaxies, and any other astronomical bodies out there.

It’s the floating black space that we see. Though tricky, it is possible to measure the temperature of an object in interstellar space.

The temperature of interstellar space is about 3 kelvins, according to NASA.

However, since interstellar space is essentially empty, there aren’t many things to interact with.

Therefore, the temperature doesn’t change much over time.

Interstellar space is one of the few consistent temperatures in the universe because of the vacuum and lack of interaction.

Outer Space And Temperature

Outer Space And Temperature

Outer Space itself has a different temperature in most different places.

Outer space has no atmosphere, meaning that everything in outer space absorbs light equally.

In contrast, landmasses like earth and Mars reflect light back into space while absorbing light instead of reflecting it.

For example, when the planet Mercury passes through its superior conjunction (the point where it lies directly behind the Sun), the planet reflects less light than it normally would, which causes the planet to appear dimmer than normal.

Similarly, during inferior conjunction, the planet appears brighter than normal.

This phenomenon occurs because the air around the surface of our planet acts as an insulator, preventing incoming photons from getting absorbed or reflected.

This process increases the temperature of these planets, and likewise, there are similar processes that decrease temperatures.

Therefore, you can see that outer space varies in temperature because of all these different phenomena and processes occurring all at once.

We often forget that everything in space is happening all at the same time.

It’s kind of like a huge party going on up there, and we know as much as we can about it, but finding out how hot or cold air is let off helps us know an awful lot more.

Final Thoughts

Like here on earth, space is both hot and cold. The laws of the universe always call for a balance.

Earth can balance the two temperatures perfectly and work in harmony because the Sun heats it and the planet cools it off.

Earth’s temperature ranges from 12°C to 50°C. Average temperature for Earth is 33.2 degrees Celsius and 0.9 degrees Fahrenheit.

Earth’s temperature ranges from 12°C to 50°C. Average temperature for Earth is 33.2 degrees Celsius and 0.9 degrees Fahrenheit.

The average temperature on the whole Earth’s surface is considered to be 17°C to 25°C depending on if it’s summer or winter, whether it’s day or night, etc.

And people who live in much colder areas would interject about the average temperature being so high.

Whereas the average temperature of space is 3 kelvin, which is almost -270 degrees Celsius.

But don’t worry, if you were to strip away the atmosphere, we wouldn’t get anywhere near that!

Though there are still loads we don’t know about space, you have to admit that the stuff we do know is pretty cool.

So just imagine how awesome and interesting the stuff we still have yet to learn is!

Gordon Watts