The Sun
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
APODs including "The Sun"
Calm Waters and Geomagnetic Storm
09/09/2017
Very recognizable stars of the northern sky are a backdrop for calm waters in this moonlit sea and skyscape off Cape Cod, Massachusetts. Taken on September 7, the photo also records a colorful display of northern lights or aurora borealis triggered by a severe geomagnetic storm. Visible crossing the Sun, the giant solar active region responsible, AR 2673, is much larger than planet Earth. It has produced the strongest flare of the current solar cycle and and the Earth-directed coronal mass ejection in the last few days.