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The age of the Sun cannot be measured directly; one way to estimate it is from the age of the oldest meteorites, and models of the evolution of the Solar System. [1] The composition in the photosphere of the modern-day Sun, by mass, is 74.9% hydrogen and 23.8% helium. [2]
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 halfway through its life cycle.
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]
The Sun will spend a total of approximately 10 to 11 billion years as a main-sequence star before the red giant phase of the Sun. [135] At the 8 billion year mark, the Sun will be at its hottest point according to the ESA's Gaia space observatory mission in 2022. [136]
Specifically, using 1-D models, which represent Earth as a single point (instead of something that varies across 3 dimensions) scientists have determined that at 4.5 Ga, with a 30% dimmer Sun, a minimum partial pressure of 0.1 bar of CO 2 is required to maintain an above-freezing surface temperature; 10 bar of CO 2 has been suggested as a ...
The core contains 34% of the Sun's mass, but only 3% of the Sun's volume, and it generates 99% of the fusion power of the Sun. There are two distinct reactions in which four hydrogen nuclei may eventually result in one helium nucleus: the proton–proton chain reaction – which is responsible for most of the Sun's released energy – and the ...
Astronomers used the Hubble Space Telescope to make a landmark discovery of water vapor in the atmosphere of a planet just twice Earth’s diameter in size.
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 ...