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
13/07/2020
This sight was worth getting out of bed early. Comet C/2020 F3 (NEOWISE) has been rising before dawn during the past week to the delight of northern sky enthusiasts awake that early. Up before sunrise, the featured photographer was able to capture in dramatic fashion one of the few comets visible to the unaided eye this century, an inner-Solar System intruder that might become known as the Great Comet of 2020. The resulting video details Comet NEOWISE from Italy rising over the Adriatic Sea. The time-lapse video combines over 240 images taken over 30 minutes. The comet is seen rising through a foreground of bright and undulating noctilucent clouds, and before a background of distant stars. Comet NEOWISE has remained unexpectedly bright, so far, with its ion and dust tails found to emanate from a nucleus spanning about five kilometers across. Fortunately, starting tonight, northern observers with a clear and dark northwestern horizon should be able to see the sun-reflecting interplanetary snowball just after sunset. Notable Images of Comet NEOWISE Submitted to APOD: || July 12 || July 11 || July 10 & earlier ||