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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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Troy (Ancient Greek: Τροία, Troía, Ἴλιον, Ílion or Ἴλιος, Ílios; Latin: Troia and Ilium; Hittite: ???? Wilusa or ???? Truwisa; Turkish: Truva or Troya) was a city in the northwest of Asia Minor (modern Turkey), southwest of the Çanakkale Strait, south of the mouth of the Dardanelles and northwest of Mount Ida. The location in the present day is the hill of Hisarlik and its immediate vicinity. In modern scholarly nomenclature, the Ridge of Troy (including Hisarlik) borders the Plain of Troy, flat agricultural land, which conducts the lower Scamander River to the strait. Troy was the setting of the Trojan War described in the Greek Epic Cycle, in particular in the Iliad, one of the two epic poems attributed to Homer. Metrical evidence from the Iliad and the Odyssey suggests that the name Ἴλιον (Ilion) formerly began with a digamma: Ϝίλιον (Wilion); this is also supported by the Hittite name for what is thought to be the same city, Wilusa. According to archaeologist Manfred Korfmann, Troy's location near the Aegean Sea, as well as the Sea of Marmara and the Black Sea, made it a hub for military activities and trade, and the chief site of a culture that Korfmann calls the "Maritime Troja Culture", which extended over the region between these seas.The city was destroyed at the end of the Bronze Age – a phase that is generally believed to represent the end of the Trojan War – and was abandoned or near-abandoned during the subsequent Dark Age. After this, the site acquired a new, Greek-speaking population, and the city became, along with the rest of Anatolia, a part of the Persian Empire. The Troad was then conquered by Alexander the Great, an admirer of Achilles, who he believed had the same type of glorious (but short-lived) destiny. After the Roman conquest of this now Hellenistic Greek-speaking world, a new capital called Ilium (from Greek: Ἴλιον, Ilion) was founded on the site in the reign of the Roman Emperor Augustus. It flourished until the establishment of Constantinople, became a bishopric, was abandoned, repopulated for a few centuries in the Byzantine era, before being abandoned again (although it has remained a titular see of the Catholic Church).