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The faint young Sun paradox or faint young Sun problem describes the apparent contradiction between observations of liquid water early in Earth's history and the astrophysical expectation that the Sun's output would have been only 70 percent as intense during that epoch as it is during the modern epoch. [1]
Once the Sun changes from burning hydrogen within its core to burning hydrogen in a shell around its core, the core will start to contract, and the outer envelope will expand. The total luminosity will steadily increase over the following billion years until it reaches 2,730 times its current luminosity at the age of 12.167 billion years.
The Sun's luminosity will have increased by 35–40%, causing all water currently present in lakes and oceans to evaporate, if it had not done so earlier. The greenhouse effect caused by the massive, water-rich atmosphere will result in Earth's surface temperature rising to 1,400 K (1,130 °C; 2,060 °F), which is hot enough to melt some ...
The expanding Sun is expected to vaporize Mercury as well as Venus, and render Earth and Mars uninhabitable (possibly destroying Earth as well). [31] [32] Eventually, the core will be hot enough for helium fusion; the Sun will burn helium for a fraction of the time it burned hydrogen in the core. The Sun is not massive enough to commence the ...
A plasma enters what scientists call the burning plasma regime when the self-heating power exceeds any external heating. [1] The Sun is a burning plasma that has reached fusion ignition, meaning the Sun's plasma temperature is maintained solely by energy released from fusion. The Sun has been burning hydrogen for 4.5 billion years and is about ...
In the spectral class label, G2 indicates its surface temperature, of approximately 5770 K ( the UAI will accept in 2014 5772 K) and V indicates that the Sun, like most stars, is a main-sequence star, and thus generates its energy via fusing hydrogen into helium. In its core, the Sun fuses about 620 million metric tons of hydrogen each second.
Instead, when it runs out of hydrogen in the core in approximately 5 billion years, core hydrogen fusion will stop, and there will be nothing to prevent the core from contracting. The release of gravitational potential energy will cause the luminosity of the Sun to increase, ending the main sequence phase and leading the Sun to expand over the ...
In the long term, the greatest changes in the Solar System will come from changes in the Sun itself as it ages. As the Sun burns through its hydrogen fuel supply, it gets hotter and burns the remaining fuel even faster. As a result, the Sun is growing brighter at a rate of ten percent every 1.1 billion years. [117]