Jupiter has been contracting and cooling down since its birth 4.6 billion years ago. It was once an incredible 700,000km (435,000 miles) in diameter — over five times its present size. Jupiter shrinks by around 2.5cm (1 in) each year, and as it does so, it generates an enormous amount of heat. Scientists now know that Jupiter gives out more heat than it receives from the Sun.
A feature that makes Jupiter interesting is that it radiates almost twice as much heat as it receives from the sun; this is possible only because it produces its own heat. Although Jupiter has almost enough hydrogen to qualify as a small star, the mysterious excess heat has another explanation: The planet is warmed by energy left over from its formation 4.6 billion years ago.
Jupiter is five times farther from the sun than the Earth is; at this great distance, it receives a fraction of the sun’s warming rays, keeping the planet very cold. Based on the energy Jupiter receives from the sun, astronomers expected it to have a temperature of 105 kelvins (minus 271 degrees Fahrenheit). But an analysis of the infrared light and radio waves received from Jupiter revealed its temperature to be 125 kelvins (minus 235 degrees Fahrenheit). To account for the difference, Jupiter must be generating its own heat at a rate comparable to what it receives from the sun.
During the solar system’s earliest years, Jupiter and the other planets formed through the force of gravity; clouds of gas and dust particles contracted under their own weight, eventually becoming solid bodies with atmospheres. Unlike most of the planets, Jupiter, whose volume is mostly gas, is still contracting. As its material falls toward the planet’s center, it releases stored gravitational energy, eventually becoming heat.
Picture Credit : Google
