The Sun is a yellow dwarf star (G2V), about 4.6 billion years old, and the dominant gravitational force in the Solar System. It has a diameter of roughly 1.4 million kilometers and contains around 99.8% of the Solar System’s mass. Nuclear fusion in its core converts hydrogen into helium, producing energy that warms the planets. Above the core lie the radiative and convective zones, followed by the visible photosphere (~5,500 °C), the chromosphere, and the much hotter corona (~2 million °C).
Source: science.nasa.gov
28/05/2024
It's back. The famous active region on the Sun that created auroras visible around the Earth earlier this month has survived its rotation around the far side of the Sun -- and returned. Yesterday, as it was beginning to reappear on the Earth-facing side, the region formerly labeled AR 3664 threw another major solar flare, again in the highest-energy X-class range. The featured video shows the emerging active region on the lower left, as it was captured by NASA's Earth-orbiting Solar Dynamics Observatory yesterday in ultraviolet light. The video is a time-lapse of the entire Sun rotating over 24 hours. Watch the lower-left region carefully at about the 2-second mark to see the powerful flare burst out. The energetic particles from that flare and associated CME are not expected to directly impact the Earth and trigger impressive auroras, but scientists will keep a close watch on this unusually active region over the next two weeks, as it faces the Earth, to see what develops.