WHAT ARE THE COLDEST AND THE HOTTEST OBJECTS IN THE UNIVERSE?
Absolute zero, the temperature at which thermal energy is theoretically zero and which is therefore generally considered the coldest possible temperature, is -273.15°C Celsius (or 0°K on the absolute Kelvin scale). The cosmic microwave background radiation which uniformly permeates all of space has a temperature of 2.725°K, or around -270°C.
Within the Solar System, the average temperature on Pluto is around -235°C, on Neptune around -220°C, on Uranus -210°C, on Saturn -184°C and on Jupiter -153°C. The temperature on Mars varies between about -87°C and -5°C, with an average of around -46°C. The lowest natural temperature on Earth (recorded at Vostok, Antarctica in 1983) is -89°C; the highest surface temperature on Earth (recorded at Al 'Aziziyah, Libya in 1922) is 58°C; the mean overall temperature on Earth is 14°C.
Water at standard pressure on Earth freezes at 0°C, and boils at 100°C. Lead melts at around 328°C, iron at 1,535°C, titanium at 1,668°C, and carbon in the range of 3,550°C to 3,675°C depending on the type. The temperature of an incandescent light bulb is round 2,200°C. A lightning bolt can reach 28,000°C. The temperature in a working fusion reactor is around 100 million °C. The highest man-made temperature, about 2 billion °C, was generated by the so-called Z-Machine at the Sandia National Laboratories in Albuquerque, New Mexico.
Continuing through the Solar System, the mean daytime temperature on the Moon is 107°C, while the mean nighttime temperature is -153°C. The temperature on Venus is a relatively uniform 462°C. The surface temperature on Mercury varies between 466°C on the sunward side and -184°C on the other side. The surface of the Sun has a temperature of about 5,700°C, and the core of the Sun about 15 million °C (although the temperature in the Sun’s corona can rise to over 2 million °C).
Red dwarf and red giant stars typically have surface temperatures in the range of 2,500°C to 3,500°C. Blue supergiant and hypergiant stars have surface temperatures ranging anywhere from 3,500°C to 35,000°C. The explosion of a supernova can generate temperatures in excess of 100 billion °C. The Planck Temperature is the temperature of the universe at 1 Planck Time after the Big Bang, and is considered the de facto maximum possible temperature. It has been calculated to be approximately 1.4 × 1032°C (140,000,000,000,000,000,000,000,000,000,000°C).