In the article, K stands for Kelvin, which is one of the units to measure temperature. The relation between K and °C is: K = °C + 273.15 Temperature is one of the most important property of celestial objects that can be used to study the characteristics of the objects. The Space itself is vacuum and is very cold. There are a variety of objects in Space, some hot and some cold. This video will give an insight about how cold or how hot the objects in Space can get!
Planck temperature was only achieved once, i.e few seconds after the big bang. At ‘0’ Kelvin level, all molecular motion ceases down and this temperature can never be achieved.
Man has been successful in creating some of the lowest and highest temperature other than absolute zero and Planck temperature.