The exosphere is almost a vacuum. Objects in the exosphere, like the Hubble Space Telescope (shown here), can be very hot when exposed to scorching sunlight or extremely cold when immersed in shadow.
Click on image for full size
Image courtesy NASA.

Temperature in the Exosphere

The exosphere is very nearly a vacuum. The technical definition of the temperature of a gas (even a very thin one) is related to the average speed of particles (atoms and molecules). Since most of the particles in the exosphere are moving very fast, the temperature there is technically quite high. However, objects in the exosphere don't really "feel" much heat from the particles - there are simply too few gas particles, no matter how quickly they fly about, to transfer much heat to the objects they collide with. In general, the exosphere would feel very, very cold to us.

The temperature of most objects (like satellites) in the exosphere depends on whether they are lit by sunlight or are kept dark in shade. Objects lit by the intensely bright sunlight in the exosphere can become very, very hot. However, objects (or parts of objects) in shade tend to get very, very cold.

Last modified April 6, 2009 by Randy Russell.

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Molecules

Most things around us are made of groups of atoms bonded together into packages called molecules. The atoms in a molecule are held together because they share or exchange electrons. Molecules are made...more

Rainbows

Rainbows appear in the sky when there is bright sunlight and rain. Sunlight is known as visible or white light and is actually a mixture of colors. Rainbows result from the refraction and reflection of...more

The Four Seasons

The Earth travels around the sun one full time per year. During this year, the seasons change depending on the amount of sunlight reaching the surface and the Earth's tilt as it revolves around the sun....more

Research Aircraft

Scientists sometimes travel in specially outfitted airplanes in order to gather data about atmospheric conditions. These research aircraft have special inlet ports that bring air from the outside into...more

Anemometer

An anemometer is a weather instrument used to measure the wind (it can also be called a wind gauge). Anemometers can measure wind speed, wind direction, and other information like the largest gust of wind...more

Thermometer

Thermometers measure temperature. "Thermo" means heat and "meter" means to measure. You can use a thermometer to measure the temperature of many things, including the temperature of...more

Weather Balloons

Weather balloons are used to carry weather instruments that measure temperature, pressure, humidity, and winds in the lowest few miles of the atmosphere. The balloons are made of rubber and weigh up to...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA