8/31/2023 0 Comments His solar orbiterBut the probe never got closer than 1.2 astronomical units. Two decades ago, ESA and NASA’s Ulysses probe flew outside the ecliptic plane in which the planets orbit and found surprising uniformity across the Sun’s global magnetic field. (Latitude on the Sun is referred to as heliographic latitude, with 0° at its equator and 90° at its north pole.) To determine the relationship between the dynamo and the interior, researchers need details about the movement of material beneath the Sun’s surface at different latitudes on the star. Currently, astronomers believe the dynamo lies in a 12,000-mile-deep (19,300 km) shear zone between the radiative and convective regions of the Sun’s interior, where rotational velocities shift markedly. One such enigma is the solar dynamo - an elusive mechanism thought to induce the Sun’s global magnetic field. NASA’s Solar Dynamics Observatory sharpened our awareness of how this magnetism is created, stored, and released.īut for all we know about our star, there are still mysteries left to unlock. Ultraviolet data from SOHO and the Japanese Institute of Space and Astronautical Science’s Yohkoh probe revealed the role of thin, magnetized loops in heating and accelerating coronal plasmas. The joint ESA/NASA Solar and Heliospheric Observatory (SOHO) and NASA’s Transition Region and Coronal Explorer showed the Sun’s energetic vigor ebbs and flows in tight lockstep with each 11-year cycle of solar activity. Spacecraft have watched the Sun from afar for five decades, spotting shock waves, flares, and coronal mass ejections (CMEs) that unleash huge quantities of plasma and internal magnetism into the bubblelike heliosphere that surrounds the planets. Temperatures cool to 5,800 kelvins (9,980 degrees Fahrenheit ) at its visible surface (the photosphere), then climb precipitously from 10,000 to 1 million-plus kelvins in its glowing corona, which appears like an effervescent veil during solar eclipses. A core more than 13 times denser than lead and 25 times wider than Earth generates temperatures of 15.6 million kelvins, hot enough to fuse hydrogen into helium and transform millions of tons of matter into energy every second. Instruments on the ground and in space have opened an insightful window into its throbbing interior. Yet only recently have astronomers and physicists come to theoretical grips with the Sun’s true nature: a broiling sphere of plasma comprising three-quarters hydrogen and one-quarter helium, and the singular reason for earthly existence. The Sun’s life-giving warmth and timekeeping beneficence objectified it for veneration from the ancient Near East to the pre-Columbian Americas. Its unwavering emergence at dawn in the east, its daily transit across the sky, and its disappearance in the west at nightfall have earned it great spiritual importance throughout history. More than 300,000 times more massive than Earth and 864,400 miles (1.4 million kilometers) in diameter, the Sun holds 99.86 percent of the mass in the solar system. A stable G-type star on the cusp of middle age, it is fast approaching the halfway point in an evolution that has seen life sprout on at least one of its planetary retinue. More than 4.6 billion years old, the Sun is the heart of our solar system.
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