## Gravity Wiki

771pages on
this wiki

Surface temperature(Ts) is dependent on the heat flow from inside and other astonomic object. Heat flows through thermal conduction and radiation from inside and through radiation from outside.

## Physical quantityEdit

It is important to check physical meaning of $M_i T_s /T_0$ which is  gravitational mass.  The value is proportional to the pressure for ideal gas.

The Physical quantity is proportional to the radiational pressure for solid.

## In interplanetary space Edit

Radiation pressure is about 10-5 Pa at Earth's distance from the Sun[1] and decreases by the square of the distance from the Sun.

For example, at the boiling point of water (T = 373.15 K), the pressure only amounts to 3 micropascals (about 2 pounds force per square mile). If the radiation is directional (in interplanetary space, the overwhelming proportion of the energy flux comes from the Sun alone), the radiation pressure is tripled, to σT4/c; if the body is a perfect reflector, the pressure can be doubled again, to 2σT4/c. A solar sail at the distance where the equivalent radiation temperature is the boiling point of water could thus achieve about 22 µPa, or nearly 13 lbf/sq mi. Such feeble pressures are, nevertheless, able to produce marked effects upon minute particles like gas ions and electrons, and are important in the theory of electron emission from the Sun, of cometary material, and so on (see also: Yarkovsky effect, YORP effect).