The Sun is composed primarily of the chemical elements hydrogen and helium, which account for 74.9% and 23.8% of the mass of the Sun in the photosphere, respectively. The energy of this sunlight supports almost all life on Earth by photosynthesis, and drives Earth’s climate and weather. The mean distance of the Sun to Earth is approximately 1 astronomical unit or AU (150,000,000 km/93,000,000 mi), though this changes due to variations in Earth’s orbit.Īt this average distance, light travels from the Sun to Earth in about 8 minutes and 19 seconds. The Sun is by far the brightest object in the sky, with an apparent magnitude of -26.74, which is about 13 billion times brighter than the next brightest star (Sirius, which has an apparent magnitude of -1.46). And then at the high point of the cycle, solar maximum, there are the most sunspots and the greatest amount of solar activity. At the low point, called solar minimum, there are few, if any sunspots. The amount of activity on the Sun rises and falls over an 11-year cycle. Sunspots appear in cycles and sometimes there are none visible at all.Ĭoronal mass ejections and solar flares occur when these magnetic field lines snap and reconfigure. The darker sunspots – cooler areas which last for a few months and vary greatly in size – are created when magnetic field lines pierce through the Sun’s photosphere. It has north and south magnetic poles like the Earth, and the magnetic field lines create the activity we see on the surface. Within the center, temperature are estimates to be as high as 15.7 million K (15,699,726.85 million ☌/28,259,540.33 million ☏), while the Corona experiences temperatures of about 5 million K (4,999,726.85 ☌/ 8,999,540.33 ☏), and the visible surface (photosphere) reaches an effective temperature of 5778 K (5504.85 ☌/9940.73 ☏).īecause the Sun is made of plasma, it’s also highly magnetic. The Sun is a member of the Population I group of stars, which describes luminous, hot, and young stars that are typically found in the spiral arms of galaxies.Įstimates of the Sun’s temperature also vary the closer one gets to its core. Our Sun is brighter than most of the other stars in the galaxy (which are also red dwarfs) and only about 5% of stars in the Milky Way are larger than the Sun. It merely appears to be yellow because of the effect of the atmosphere. However, models of the Sun estimate that it has a density of 162.2 g/cm 3 closer to the core, which is 12.4 times that of Earth.Īlthough our Sun appears to be yellow, it is actually white. On average, it has a density of 1.408 g/cm 3, which is roughly one-quarter that of Earth. With a diameter of 696,342 ± 65 km and a mass of approximately 1.988 × 10 30 kg (1.9 trillion quadrillion metric tons), the Sun is 109 times as large as Earth and 333,000 times as massive.īeing a star, the Sun’s density varies considerably between its outer layers and its core. The Sun has an absolute magnitude of +4.83, which is estimated to be brighter than about 85% of the stars in the Milky Way – most of which are red dwarfs. The Sun is a G-type main-sequence star that comprises about 99.86% of the mass of the Solar System. However, the adjectival form solar is used widely to refer to phenomena or attributes pertaining to the Sun. The Latin name for the Sun, Sol, is widely known but is not in common use. This name resulted from the Germanic interpretation of Latin dies solis, which is itself a translation of the Greek heméra helíou. The English name for Sunday stems from the Old English Sunnandæg (literally “Sun’s day”) which was in use before 700 CE. All Germanic terms for the Sun stem from the Proto-Germanic “ sunnon“, which is in turn derived from the sauelor sauol of Proto-Indo-European. Other Germanic forms of the name – ranging from sunne and sonne in Old Frisian to sunna in Old High German and Old Norse to sunno in Gothic. The name “The Sun” is a proper English noun which evolved from the Old English sunne, which may be related to the word south. But that has done nothing to diminish it’s significance. In time, our understanding of the Sun has changed and become increasingly empirical. From the Aztecs, Mayans and Incas to the ancient Sumerians, Egyptians, Greeks, Romans and Druids, the Sun was a central deity because it was seen as the bringer of all light and life. Since the beginning of history, human beings have understood the Sun’s importance to our world, it’s seasons, the diurnal cycle, and the life-cycle of plants.īecause of this, the Sun has been at the center of many ancient culture’s mythologies and systems of worship. It accounts for more than 99.86% of the mass of the Solar System and it’s gravity dominates all the planets and objects that orbit it. The Sun is the center of the Solar System and the source of all life and energy here on Earth.
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