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The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy mainly as light and infrared radiation. It is by far the most important source of energy for life on Earth. Its diameter is about 1.39 million kilometres (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 consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron.The Sun is a G-type main-sequence star (G2V) based on its spectral class. As such, it is informally and not 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. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core. It is thought that almost all stars form by this process.
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Gifu (岐阜市, Gifu-shi) is a city located in the south-central portion of Gifu Prefecture, Japan, and serves as the prefectural capital. The city has played an important role in Japan's history because of its location in the middle of the country. During the Sengoku period, various warlords, including Oda Nobunaga, used the area as a base in an attempt to unify and control Japan. Gifu continued to flourish even after Japan's unification as both an important shukuba along the Edo period Nakasendō and, later, as one of Japan's fashion centers. It has been designated a core city by the national government.
Located on the alluvial plain of the Nagara River, Gifu has taken advantage of the surrounding natural resources to create both traditional industries (including Mino washi and agriculture) and tourism opportunities such as cormorant fishing. Mount Kinka, one of the city's major symbols, is home to a nationally designated forest and Gifu Castle, a replica of Nobunaga's former castle.