The average temperature of space is approximately -270 degrees Fahrenheit. Since space is a vacuum, it is subject to forces called radiation pressure, which keeps the temperature down.
The temperature of outer space is 4 degrees Kelvin, or -460 degrees Fahrenheit. For years, scientists have speculated what the average temperature of space is, but it wasn’t until 2007 that the answer was finally discovered. Thanks to NASA’s Spitzer Space Telescope, scientists were able to measure the infrared light emitted by stars throughout the universe, then use that data to estimate the average temperature of space. What did they discover? The space is very cold.
The known universe is about 93 percent hydrogen and 7 percent helium, with trace amounts of other elements such as lithium, oxygen, carbon, and nitrogen. By comparison, water is 70 percent hydrogen and 30 percent oxygen, so space is about 1,400 degrees Fahrenheit hotter than the warmest place on Earth. Despite the temperature differences, Earth’s average temperature is about 65 degrees Fahrenheit, and as NASA explains, the temperature in space stays rather constant, within 0.1 degrees Fahrenheit of its average.
Can You Feel Temperature In Space?
People have always been fascinated by the stars. They wonder about them, make the patterns in the sky, make constellations, and guess at the planets and worlds that orbit those stars. But did you know that some of the stars are actually hot and that other than the stars, other things make our space look the way it does?
The instruments that measure temperatures in space float in microgravity, so their temperature sensors aren’t affected by convection, which tends to warm objects in space. All the instruments are mounted on the outside of the satellites, and the temperature is measured by a thermal imager, which essentially sees heat. Since there is only slight motion in microgravity, the sensors sense only the average temperature of the objects around them.
Why Is Space Cold When The Sun Is Hot?
Space is cold, despite the fact that the sun is so hot. How can this be? Two major factors explain how space can be cold while the sun is hot—the sun’s radiation and the Sun-Earth Extreme Ultraviolet (XUV) Connection (SECC). The radiation from the sun continually bombards Earth, causing air temperatures to rise above what would otherwise be normal.
When the sun is shining, it can get hot outside. But outer space is much colder than you think. As you know, the sun is a giant ball of plasma and charged particles. The solar wind that reaches Earth consists mostly of protons and electrons, but some of the particles actually come from the sun’s corona (the outer atmosphere). The sun’s corona is made up of plasma, a very electrically charged gas. When the sun’s charged particles hit atoms in Earth’s atmosphere, they strip electrons off those atoms. The result is a positive charge, which collects into clouds. These clouds are called “coronal mass ejections” or “CMEs,” They can sometimes create flashes of light, called auroras.
One of the most fundamental questions in astrophysics is, “What is the Universe made of?” The answer to this question is central to understanding the nature of the universe because, as Einstein noted, “the whole of physics can be summarized in the equations that relate energy, mass, and time.” Researchers are continuously discovering new elements in the universe, and the rate at which new elements are being discovered is increasing.
While exploring the far reaches of the universe, humanity has begun to prove—and disprove—what it has long suspected: Space is cold. A vast emptiness where the sun, planets, and stars shine, space has fascinated humans since ancient times.
