The colder the temperature, the less motion. Absolute absence of heat is measured as zero on the Kelvin scale. The coldest regions of interstellar space are believed to reach a minimum of 3 degrees K.
The monstrous blizzard that swept the united States this past week, spreading snow and ice from the Midwest to the Northeast, tests the endurance of many of us with memories of warmer temps seeming to be so distant. Yet it could always be worse –– at least we are on Earth.
It’s a cold time out there in the universe. Oh, if you venture anywhere near a star, it gets mighty hot, but the vast expanse between stars is frigid beyond our common understanding of cold.
Ice can be found in the dark recess of the lunar poles, on mars and covering some moons of the outer giant planets. Comets, made largely of dusty ice, inhabit the far reaches and occasionally swoop close by the sun in a burst of glory.
We now know the famous ring system of Saturn is made of ice. Before, astronomers thoguht the rings were made up of rocky debris, either from a moon that ventured too close and broke asunder, or debris left over from the formation of the planet.
Our knowledge of the Saturnian system has abounded since Cassini spacecraft arrived in orbit in 2004 and is still exploring the planets and its family of moons seven years later. The average temperature on Saturn is minus 300 degrees. If you go out as far as Neptune, the temperature dips to minus 370.
How cold is space? Temperature is a measure of heat, shown by the vibration of molecules. The colder the temperature, the less motion. Absolute absence of heat is measured as zero on the Kelvin scale. The coldest regions of interstellar space are believed to reach a minimum of 3 degrees K. That equates to minus 454 degrees.
The hottest part of our solar system is obviously the sun, our source of heat and light and our beacon of energy that makes our planet so hospitable. The outer visible layer of the sun, known as the photosphere, is 11,000 degrees. Sunspots, which continuously form and dissipate, are relatively chilly at 7,000 degrees.
Our sun, a great churning ball of gas made of 98 percent of the mass of the solar system and big enough to hold 1.3 million Earths, is hot to the very core. In the center, the temperature is believed to be 27 million degrees. The pressure in the sun’s core, by the way, is believed to be 340 billion times the air pressure on Earth at sea level.
Stars vary widely in temperature. Our sun is about in the middle of the extremes. Blue stars are the hottest as their surfaces can reach 90,000 degrees. Red stars are the coolest, with surface temperatures of around 5,000 degrees. Stars are believed to develop through stages as they use up their fuel and change in color, luminosity and size.
Stars are so hot, yet they are so incredibly far apart that most of the universe is in deep freeze. Temperature will vary across the interstellar medium where stars warm particles of dust and gas and collisions of shock waves are emitted when material is ejected from a star.
Earth turns out to be not so bad, after all. Mercury, closest to the sun, bakes at 870 degrees, however, its dark side descends to minus 300 degrees. Venus averages 850 degrees. Mars, our nearest neighbor, can reach above the freezing point of water but is mostly well below that point, reaching minus 190 degrees. We can be glad for our friendly abode, though at times the weather can seem extreme.
First quarter moon is on Feb. 11. Keep looking up!
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