Temperature of Space

[stevo247]

What is the temperature of space just beyond the earths atmosphere?

[Phi for All]

What is the temperature of space just beyond the earths atmosphere?

If you mean the temperature of space with no influence from planetary matter, I believe it's just under 3 degrees Kelvin. There's always some background radiation giving some warmth.

[D H]

What is the temperature of space just beyond the earths atmosphere?

The answer is "it depends". First, it depends on what you mean by "just beyond the earth's atmosphere". Second it depends on what you mean by "temperature".

 

The standard definition of the boundary between the Earth's atmosphere and outer space is the "Kármán line" (wikipedia article here), or 100 km above the surface of the Earth. There is still some air up there, very very thin air, but air. This chart shows the temperature of the molecules/ions that form the upper reaches of the atmosphere. Note that the temperature starts climbs from 300K to over 1200K as altitude increases. The Earth's atmosphere effectively ends at around 10,000 km above the Earth. This is still not empty space. The heliosphere (diagram here) extends from the surface of the Sun to the 60 to 150 AU from the Sun. The heliosphere is even hotter than the Earth's upper atmosphere. What's outside the heliosphere? The solar system appear to be in a "cool" bubble (~ 7000 K) embedded in very hot bubble (millions of kelvins) of space (reference here).

 

So space (at least local space) is "hot". I earlier said the answer depends on what you mean by temperature. I answered with the temperature of the plasma that forms the Earth's upper atmosphere, the heliosphere, and the local interstellar medium. Those temperatures are more than a bit misleading. A spaceship will not get nearly as hot as the surrounding medium because that medium is so incredibly thin. If the spacecraft is shielded from sunlight, it will cool to around 2.7 kelvins. There is very, very little heat transfer from the thin exoatmosphere to the spacecraft. There is even less heat transfer from the interplanetary or interstellar medium. In this sense, space is very, very cold.

[swansont]

Technically there's no temperature of space, there's isotropic radiation in it that looks thermal, and appears to be from a source that's at a temperature of 2.7 K. Near the earth there is going to be addition radiation from the earth, a source that's around 300 K, and the sun. These two sources are not isotropic.

 

What you might ask is "what temperature would an object reach if placed in space" and that would be "about 63 ºC, depending on details" if it's due to the sun, near the orbit of the earth. It gets about 1.4 kW/m^2 of energy, and re-radiates that (with twice the area, if it's a sheet) according to the Stefan-Boltzmann equation. Geometry, and other details, will matter.

 

http://en.wikipedia.org/wiki/Stefan-Boltzmann_law

[D H]

Technically there's no temperature of space

Cosmologists would strongly disagree with this statement. They model the "stuff" that occupies interplanetary, interstellar, and intergalactic space as an atmosphere. A very, very thin atmosphere, but an atmosphere nonetheless. It has a non-zero density and the individual ions have a non-zero random component to their velocities (i.e., temperature). The medium can even conduct sound (very low frequency sound).

 

The key problem with calling this temperature is that it might lead one to think that some macro-sized object will eventually come into thermal equilibrium with the surrounding medium. That doesn't happen, of course. The temperature of a macro-sized object in space depends on the thermal radiation of the object and on how much energy it receives from sunlight. The temperature of the medium itself plays almost no part in the temperature of some macro-sized object. Thinking that it might play a part does not invalidate the concept of "temperature" in outer space. Thinking in such a way is yet another demonstration of the faults that result from extrapolating our earth-based intuitions to regimes far removed from those intuitions. We similarly get in trouble if we apply our earthly intutions to regimes of very high velocity, very large mass, or very small scale.

[stevo247]

What is the "temperature of the medium" beyond the reaches of the earths atmosphere (about 11,000 to 12,000 miles away from earth)?

[swansont]

Cosmologists would strongly disagree with this statement. They model the "stuff" that occupies interplanetary, interstellar, and intergalactic space as an atmosphere.

 

And that would be the stuff "in" space, not "space" itself. (The "technically" part was implying I was about to get pedantic)

[D H]

What is the "temperature of the medium" beyond the reaches of the earths atmosphere (about 11,000 to 12,000 miles away from earth)?

At around 1AU the interplanetary medium is very hot: around 100,000 kelvins. It varies a lot (plus or minus 50,000 kelvins) with changes in the solar wind. This high temperature "gas" has very little heat content (yes, I know this is an abuse of terminology, so don't pounce on me, swan), meaning that a macro-sized object such as a spacecraft will not warm up to 100,000 kelvins because of contact with the gas. Thermal radiation and absorption of electromagnetic radiation are almost all that matters when it comes to predicting temperature variations of a macro-sized object.

[swansont]

And accounting for the solar radiation, as I said before, if you plopped a flat panel in space, facing the sun, it would heat up to about 60-65 ºC. Beyond that level of detail, you'd need to specify the object and its orientation, geometry, etc.

[thedarkshade]

What is the temperature of space just beyond the earths atmosphere?

This does not refer to 'just beyond' but I've read that the average temperature of the universe is -270 C...the cold death... and IIRC due to expansion of the universe this is expected to continue decreasing.

 

So will absolute zero be reached in a natural way?... I don't know... perhaps, but thermodynamics still says it can't!

[stevo247]

If you could freeze a moment in time, and draw a straight line from the earth to the sun; would it be possible to determine the temperature change from the earth, through the atmosphere, into space, and then as close to the sun as possible, using the typical spacecraft that can fly to mars, etc. if an object is needed to determine temperature? Where would the big temperature changes take place?

[Daecon]

This high temperature "gas" has very little heat content

I don't understand what that means.

 

How can something have a temperature of 100,000 K but not be hot?

[swansont]

I don't understand what that means.

 

How can something have a temperature of 100,000 K but not be hot?

 

Very energetic, but very few molecules. The heat capacity is small.

 

If you could freeze a moment in time, and draw a straight line from the earth to the sun; would it be possible to determine the temperature change from the earth, through the atmosphere, into space, and then as close to the sun as possible, using the typical spacecraft that can fly to mars, etc. if an object is needed to determine temperature? Where would the big temperature changes take place?

 

I'm not sure if I understand the question.

 

Temperature change in space is something for which satellites have to be designed, so you could try and look that up. The moon swings between about 125 ºC and -145 ºC. The minimum temperature for something shielded from the sun is going to be even lower.

[stevo247]

I think I need to re-examine my understanding of “temperature” and “heat”. On earth you can take a thermometer to the north pole and get an objective reading, and that reading would correspond to your subjective impression. You could then go to the equator and the objective reading on the thermometer would also correspond to your subjective impression. But it seems difficult to determine the objective temperature of space relative to our sensory impressions.

 

What I am trying to determine, is the temperature change from the sun to the earth. For example, the sun is really hot (I think). Does it radiate heat for x amount of miles into space? Then, is there a great distance in space where it is relatively cold? Then, when the suns light interacts with the earths atmosphere, does the temperature increase? And then, descending through the earths atmosphere, does the temperature start to decrease?

[Klaynos]

Most temperatures you will see on earth are temperatures in the shade... this is an important note...

 

I think the intensity of the sun drops off as 1/r² but I'm not 100% sure...

[Realitycheck]

I think I need to re-examine my understanding of “temperature” and “heat”. On earth you can take a thermometer to the north pole and get an objective reading, and that reading would correspond to your subjective impression. You could then go to the equator and the objective reading on the thermometer would also correspond to your subjective impression. But it seems difficult to determine the objective temperature of space relative to our sensory impressions.

 

What I am trying to determine, is the temperature change from the sun to the earth. For example, the sun is really hot (I think). Does it radiate heat for x amount of miles into space? Then, is there a great distance in space where it is relatively cold? Then, when the suns light interacts with the earths atmosphere, does the temperature increase? And then, descending through the earths atmosphere, does the temperature start to decrease?

 

 

 

The further you get away from the sun, the less radiation will hit you, since it will be more widely dispersed. Being on a planet, the atmosphere absorbs much of the radiation, since it is effectively in the way. If you are out in space and in the dark, there is no radiation coming at you, or very little, hence it will be very cold.

 

I gather from swanson's statement that, at our orbit around the sun, if we were to take off our spacesuit in the sunlight in empty space, it would feel like 60 C, too hot and disregarding all kinds of harmful radiation which the earth's atmosphere would normally filter out. The further we go out, this temperature would lessen, despite this harmful radiation. The moment that we step into the shade, however, would immediately plunge us into temperatures near 3 K, since we have no atmosphere buffering the temperature.

 

Does this sound right?

[swansont]

The further you get away from the sun, the less radiation will hit you, since it will be more widely dispersed. Being on a planet, the atmosphere absorbs much of the radiation, since it is effectively in the way. If you are out in space and in the dark, there is no radiation coming at you, or very little, hence it will be very cold.

 

I gather from swanson's statement that, at our orbit around the sun, if we were to take off our spacesuit in the sunlight in empty space, it would feel like 60 C, too hot and disregarding all kinds of harmful radiation. The further we go out, this temperature would lessen, despite this extremely harmful radiation. The moment that we step into the shade, however, would immediately plunge us into temperatures near 3 K, since we have no atmosphere buffering the temperature.

 

Does this sound right?

 

Very roughly, yes. You wouldn't immediately drop to 3 K because you have a heat capacity and your ability to radiate drops with the temperature, and also because you still have radiation from the earth to consider.

 

I think I need to re-examine my understanding of “temperature” and “heat”. On earth you can take a thermometer to the north pole and get an objective reading, and that reading would correspond to your subjective impression. You could then go to the equator and the objective reading on the thermometer would also correspond to your subjective impression. But it seems difficult to determine the objective temperature of space relative to our sensory impressions.

 

What I am trying to determine, is the temperature change from the sun to the earth. For example, the sun is really hot (I think). Does it radiate heat for x amount of miles into space? Then, is there a great distance in space where it is relatively cold? Then, when the suns light interacts with the earths atmosphere, does the temperature increase? And then, descending through the earths atmosphere, does the temperature start to decrease?

 

One problem is that the situation you are asking about is like having a piece of metal with one end in the oven and the other end in a bucket of ice water, and you're asking what the temperature is. There is no good, general answer, unlike the examples you gave, because there will be a temperature gradient.

 

Radiation from the sun drops off as 1/r^2, as Klaynos indicated, as long as the sun seems like a point source. If all you have is radiation, and close to an ideal object, then you can use the Stefan-Boltzmann law to tell you what temperature you will reach. Other situations become more complicated as you add in other factors.

[antimatter]

What is the temperature of space just beyond the earths atmosphere?

 

The temperature in space varies with your location, for example, if you're near a star, then it will be extremely hot.

On average, the temperature is generally 4 degrees above absolute zero in space.

[Dark matter]

the temperature is only a little bit above absolute zero, because it is impossible to reach absolute zero. Also, it can heat up to almost 75 degrees C when facing the sun, because there is not atmosphere blocking you from the sun, yet it can become almost 273 degreed when away from the sun because there are virtually no photons or particles in the vacuum of space.

[antimatter]

the temperature is only a little bit above absolute zero, because it is impossible to reach absolute zero. Also, it can heat up to almost 75 degrees C when facing the sun, because there is not atmosphere blocking you from the sun, yet it can become almost 273 degreed when away from the sun because there are virtually no photons or particles in the vacuum of space.

 

Actually, there are many photons in space. If there were 'virtually no photons' then we wouldn't be able to see the moon, the stars, or anything else in space.