Sun vs Neptune - Comparison

<p>The Sun is the star at the center of the Solar System. </p>It is a sphere of plasma, with inner convective movement that generates a magnetic field by means of a dynamo process. It is by far the main source of energy for life on Earth. Its diameter is about 1.39 million kilometers (864,000 miles), or 109 times that of Earth, and its mass is about 330,000 times that of Earth. It accounts for about 99.86% of the total mass of the Solar System. Roughly three quarters of the Sun's mass is composed of hydrogen (~73%); the remainder is mostly helium (~25%), with much smaller amounts of heavier elements, including oxygen, carbon, neon, and iron.The Sun is a G-type main-sequence celebrity (G2V) based on its spectral class. As such, it's informally rather than completely accurately referred to as a yellow dwarf (its light is closer to white than yellow). It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Whereas the remainder flattened into an orbiting disk that became the Solar System, most of this matter gathered in the center. The central mass became dense and so hot that it initiated nuclear fusion. It is believed that almost all stars form by this process.

The Sun fuses about 600 million tons of hydrogen into helium every second, converting 4 million tons of matter into energy every second. This energy, which may take 170,000 and between 10,000 years to escape from its core, is the origin of the Sun's light and heat. When hydrogen fusion in its core has diminished to the point where the Sun is no more in hydrostatic equilibrium, its core will undergo a marked increase in density and temperature while its outer layers expand, eventually transforming the Sun into a red giant. It is calculated that the Sun will become sufficiently large to engulf the orbits of Venus and Mercury, and render Earth uninhabitable -- but not for about five billion years. After this, it will shed its outer layers and become a dense type of cooling star called a white dwarf, and no longer produce energy by fusion, but still glow and give off heat from its previous fusion. The Sun on Earth's effect has been recognized since ancient times, and some cultures as a deity have seen the Sun. Its orbit around the Sun and the synodic rotation of Earth will be the basis of solar calendars, among which is the calendar in use today.

Source: Wikipedia

<p>Neptune is the eighth and farthest known planet from the Sun in the Solar System. </p>In the Solar System, it is the fourth-largest planet by the third-most-massive planet diameter, and the densest giant planet. Neptune is 17 times the mass of Earth, slightly more massive than its near-twin Uranus. Neptune is physically smaller than Uranus and thicker because its mass causes gravitational compression of its atmosphere. Neptune orbits the Sun once every 164.8 years at a mean distance of 30.1 AU (4.5 billion km; 2.8 billion mi). It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune's trident. Neptune is not visible to the unaided eye and is the only planet in the Solar System found by forecast as opposed to by empirical observation. Changes in the orbit of Uranus directed Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation. The position of Neptune was calculated from Bouvard's observations by John Couch Adams and Urbain Le Verrier following his death. Neptune was observed with a telescope on 23 by Johann Galle within a degree of the position predicted by Le Verrier. Though none of the remaining 13 known moons of the planet were located before the 20th century its largest moon, Triton, was discovered soon thereafter. The distance from Earth of the planet gives it a very small apparent size, which makes it challenging to research with Earth-based telescopes. Voyager 2 visited neptune, when it flew by the planet on 25 August 1989; Voyager 2 remains the only spacecraft to visit Neptune.

The advent of the Hubble Space Telescope and large ground-based telescopes with adaptive optics has allowed for further observations from afar. Like Jupiter and Saturn, Neptune's atmosphere is composed primarily of hydrogen and helium, together with traces of hydrocarbons and possibly nitrogen, even though it includes a higher proportion of"ices" such as water, ammonia and methane. However, similar to Uranus, its interior is primarily composed of ices and rock; Uranus and Neptune are normally considered"ice giants" to emphasise this distinction. Traces of methane in the outermost areas in part account for the world's blue appearance.In contrast to the hazy, relatively featureless atmosphere of Uranus, Neptune's atmosphere has visible and active weather patterns. For example, in the time of the Voyager 2 flyby in 1989, the world's southern hemisphere had a Great Dark Spot comparable to the Great Red Spot. These weather patterns are driven by the strongest sustained winds of almost any planet in the Solar System, with recorded wind speeds as high as 2,100 km/h (580 m/s; 1,300 mph). Due to its great distance from the Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures in its cloud tops approaching 55 K (−218 °C; −361 °F). Temperatures in the world's centre are approximately 5,400 K (5,100 °C; 9,300 °F). Neptune has a faint and fragmented ring system (labelled"arcs"), which was discovered in 1984, then afterwards confirmed by Voyager 2.

Source: Wikipedia