The temperature at the visible "surface" of the Sun (top) is about 5,800 kelvins. The Sun's atmosphere is much hotter. The bottom image shows ultraviolet emissions from the Sun's atmosphere at a temperature around 70,000 kelvins.
Click on image for full size
Images courtesy of SOHO (ESA & NASA).
Kelvin Temperature Scale Used in Astronomy
The Kelvin scale is a temperature scale that is often used in astronomy and space science. You are probably more familiar with the Celsius (or Centigrade) scale, which is part of the metric system of measures, and the Fahrenheit scale, which is used in the English system.
Why do astronomers need another temperature scale? On Earth, the temperatures we most frequently encounter are often within, or close to, the range over which water is liquid. A temperature scale that has "reasonable" numbers to represent the most common temperatures encountered makes sense for day-to-day use on Earth. For example, Earth's average temperature is around 15° C (49° F). It is convenient to be able to say that tomorrow's weather will bring a high temperature of 20° C (58° F). It would not be convenient to use a scale that had very large numbers (like 6,437°) or very small or negative numbers (like 0.052° or -147°) for the most commonly encountered situations. The Celsius and Fahrenheit scales are set so that common Earthly temperatures lie in a range that lets us use "reasonable" numbers.
In space (including on other planets and moons, inside of stars, and so on), temperatures range across much more extreme values than they do on our comfortable Earth. Comets and icy moons, for example, often have temperatures close to absolute zero. Stars, on the other hand, can have temperatures of thousands of degrees or higher. The Kelvin scale avoids negative numbers altogether, so it is much more convenient to use for extremely cold temperatures. Since the size of a degree in the Kelvin and Celsius scales is just a bit larger than half a degree in the Fahrenheit scale, really hot temperatures can be represented by smaller numbers in Kelvin and Celsius than in Fahrenheit. Thus, the Kelvin scale is often the temperature scale of choice amongst astronomers and space scientists, though people in other fields sometimes use it too.
Shop Windows to the Universe Science Store!
Our online store
includes fun classroom activities
for you and your students. Issues of NESTA's quarterly journal, The Earth Scientist
are also full of classroom activities on different topics in Earth and space science!
You might also be interested in:
How did life evolve on Earth? The answer to this question can help us understand our past and prepare for our future. Although evolution provides credible and reliable answers, polls show that many people turn away from science, seeking other explanations with which they are more comfortable....more
Liquid is one of the four common states of matter. The three others are gas, solid, and plasma. There are also some other exotic states of matter that have been discovered in recent years. A liquid does...more
Not long ago, many people thought that comets were a portent that something bad was about to happen to them. Since people did not yet understand about the objects in the solar system and how they moved,...more
Triton is by far the largest moon of Neptune, and is one of the most unusual large moons in the Solar System. The poles of Triton are especially interesting. Triton has a frozen polar cap with ice geysers....more
The butterfly effect refers to how small things can have big consequences. As an example, consider two different computer simulations of the path of a hurricane. Both of them start from some initial state,...more
The Kelvin scale is a temperature scale that is often used in astronomy and space science. You are probably more familiar with the Celsius (or Centigrade) scale, which is part of the metric system of measures,...more
Infrared (IR) radiation is a type of electromagnetic radiation. Infrared "light" has a longer wavelength than visible light. Red light has a longer wavelength than other colors of light, and infrared has...more
Magnetism is a fundamental force of nature, like the force of gravity. Like gravity, which causes objects to be attracted to each other, magnetism causes magnetized objects to be attracted to each other....more