What is the hottest part of the solar system?

Answer 1

The hottest part of the solar system would certainly be within the sun. The core of the sun is estimated to exist at a temperature around 15,000,000 K. The solar envelope surrounding the core averages more around 4,000,000 K. The photosphere (the layer we get out light from) is a much cooler 6000 K. The next layer out, the chromosphere is actually hotter - around 7000 K due to the energy it absorbs. The outermost layer, the corona, varies from 1,000,000 K to 3,000,000 K - hotter than the photosphere and chromosphere, but still cooler than the core and solar envelope.

The hottest part of each of the planets is at their core. None of the planets have cores at temperatures approaching that of the core of the sun. For example, the core of the Earth is estimated to be only 5700 K - not even as hot as the coolest part of the sun). Jupiter may be around 24,000 at its core, Saturn around 12,000 K, and Uranus and Neptune around 5000 K.

Despite being closest to the sun, temperatures on the surface of Mercury only rise to a (compared to solar temperatures) balmy 427 °C (700 K) at closest approach to the sun on the side facing the sun. Venus actually has higher surface temperatures - close to 735 K due to the thick atmosphere and runaway greenhouse effect.