Understanding Vapor Pressure Laws for Astrophysics

In summary, the conversation discusses a new user's struggles with understanding an equation for a vapor pressure law, which takes the form of log(pressure) = A-(B/T). The user is unsure of the units of A and B and whether the logarithm is base ten or base e. They mention using MatLab to calculate pressure and ask for help understanding the equation. A link to various vapor pressure formulae is provided for reference.
  • #1
ZachWeiner
6
0
So, I'm new to astrophys, and I'm having trouble making a model because I don't think I understand an equation. It's a vapor pressure law, and it says it takes the form of

log(pressure) = A-(B/T)

T is in kelvins, A is 10.6, and B is 13500.

Apparently pressure ends up being dynes/cm^2.

So, first off, I don't know the units of A or B, or whether log is base ten or base e.

In MatLab, I'm saying pressure = 10^(A-(B/T))

Because I don't understand the equation, I don't know if that makes sense or not! Please help!
 
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  • #2
You can find many vapor pressure formulae (for water) here:
http ://cires.colorado.edu/~voemel/vp.html
Equation [17] there looks the closest to your formula.
Then the logarithm is natural and P is measured in Pascal.
However, you may have the logarithm on the base 10 and pressure in hectoPascals.
Pressure of what are you interested in? Is it actually water?
 

Related to Understanding Vapor Pressure Laws for Astrophysics

1. What is vapor pressure and why is it important in astrophysics?

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid form at a given temperature. In astrophysics, it is important because it helps us understand the conditions of the atmosphere and temperature of celestial bodies, as well as the evaporation and condensation of substances in space.

2. How do vapor pressure laws differ in astrophysics compared to on Earth?

Vapor pressure laws in astrophysics follow the same principles as on Earth, but they can vary greatly depending on the composition and temperature of a particular celestial body. For example, the vapor pressure of water on Earth is much higher compared to the vapor pressure of water on Mars due to the difference in atmospheric conditions.

3. Can vapor pressure be used to determine the composition of a planet's atmosphere?

Yes, vapor pressure can provide valuable information about the composition of a planet's atmosphere. By studying the vapor pressure of different substances present in the atmosphere, scientists can determine the relative abundance of these substances and gain insight into the planet's atmospheric composition.

4. How does vapor pressure change with altitude in a planet's atmosphere?

Vapor pressure generally decreases with altitude in a planet's atmosphere, as the temperature and pressure decrease with increasing altitude. However, there may be exceptions depending on the specific composition of the atmosphere and other factors.

5. Are there any other factors that can affect vapor pressure in astrophysics?

Yes, in addition to temperature and pressure, the presence of other substances and radiation can also affect vapor pressure in astrophysics. For example, the presence of certain gases in a planet's atmosphere can influence the vapor pressure of other substances, and radiation from the sun can also impact the evaporation and condensation processes in space.

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