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-------------------- 2513 - VOYAGER I , II - space explorers?
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- The Voyager discoveries is the first time that a spacecraft has directly sampled the electrically charged hazes, or plasmas, that fill both interstellar space and the solar system’s farthest outskirts. It’s another first for the spacecraft, which was launched in 1977 and performed the flybys of the ice giant planets Uranus and Neptune.
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- Launched in August and September 1977, NASA’s twin Voyager spacecraft have opened up new worlds for exploration, including Jupiter , Saturn, Uranus, and Neptune.
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- On August 17, 1981, the Voyager 2 spacecraft flew within 5.5 million miles of Saturn's rings. On January 24, 1986, it came within 50,600 miles of the ice giant Uranus. Voyager 2 completed its final planetary flyby on August 25, 1989, as it zoomed by Neptune.
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- Voyager 2’s charge into interstellar space follows that of sibling Voyager 1, which accomplished the same feat in 2012. The two spacecrafts’ data have many features in common, such as the overall density of the particles they’ve encountered in interstellar space. But intriguingly, the twin craft also saw some key differences on their way out raising new questions about our sun’s movement through the galaxy.
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- Voyagers 1 and 2 were launched “40 years ago’ on a mission to explore the outer solar system. After encountering Saturn, Voyager 1 angled upward. Voyager 2 went on to visit Uranus and Neptune before angling downward
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- To make sense of Voyager 2’s latest findings, it helps to know that the Sun isn’t a quietly burning ball of light. Our star is a raging nuclear furnace hurtling through the galaxy at about 450,000 miles an hour as it orbits the galactic center.
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- The Sun is also creates twisted, braided magnetic fields and its surface constantly throws off a breeze of electrically charged particles called the solar wind. This wind rushes out in all directions, carrying the Sun’s magnetic field with it. Eventually, the solar wind smashes into the interstellar medium which is the debris from ancient stellar explosions that lurks in the spaces between stars.
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- Like oil and water, the solar wind and the interstellar medium don’t perfectly mix, so the solar wind forms a bubble within the interstellar medium called the heliosphere.
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- Based on Voyager data, this bubble extends about 11 billion miles from the Sun at its leading edge, surrounding the Sun, all eight planets, and much of the outer objects orbiting our star. The protective heliosphere shields everything inside it, including your own fragile DNA, from most of the galaxy’s highest-energy radiation.
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- The heliosphere’s outermost edge, called the heliopause, marks the start of interstellar space. Understanding this threshold has implications for our picture of the Sun’s journey through the galaxy, which in turn can tell us more about the situations of other stars scattered across the cosmos.
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- Scientists got their first good look at the heliopause on August 25, 2012, when Voyager 1 first entered interstellar space. What they began to see left them scratching their heads.
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- For instance, researchers now know that the interstellar magnetic field is about two to three times stronger than expected, which means that interstellar particles exert up to ten times as much pressure on our heliosphere than previously thought.
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- Back in 1980, its instrument that measured the temperature of plasmas stopped working. Voyager 2’s plasma instrument is still working just fine, though, so when it crossed the heliopause on November 5, 2018, scientists could get a much better look at this border.
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- For the first time, researchers could see that as an object gets within 140 million miles of the heliopause, the plasma surrounding it slows, heats up, and gets more dense. And on the other side of the boundary, the interstellar medium is at least 54,000 degrees Fahrenheit, which is hotter than expected. However, this plasma is so thin and diffuse, the average temperature around the Voyager probes remains extremely cold.
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- Voyager 2 confirmed that the heliopause is one leaky border, and, the leaks go both ways. Before Voyager 1 passed through the heliopause, it zoomed through tendrils of interstellar particles that had punched into the heliopause like tree roots through rock. Voyager 2, however, saw a trickle of low-energy particles that extended more than a hundred million miles beyond the heliopause.
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- Another mystery appeared as Voyager 1 came within 800 million miles of the heliopause, where it entered a limbo-like area in which the outbound solar wind slowed to a crawl. Before it crossed the heliopause, Voyager 2 saw the solar wind form an altogether different kind of layer that, oddly, was nearly the same width as the stagnant one seen by Voyager 1.
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- Solving these puzzles will require a better view of the heliosphere as a whole. Voyager 1 exited near the heliosphere’s leading edge, where it collides with the interstellar medium, and Voyager 2 exited along its left flank.
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- We have no data on the heliosphere’s wake, so its overall shape remains a mystery. The interstellar medium’s pressure might keep the heliosphere roughly spherical, but it’s also possible that it has a tail like a comet, or that it is shaped like a croissant.
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- But while other spacecraft are currently outward bound, they won’t be able to return data from the heliopause. NASA’s New Horizons spacecraft is zooming out of the solar system at more than 31,000 miles an hour, and when it runs out of power in the 2030s, it’ll fall silent more than a billion miles short of the heliosphere’s outer edge.
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- Space missions need much patients. Not just to get there , but to analyze all the data and to try to make sense of what we learn. The farther we go the behinder we get. Much more to learn. Students, are you ready?
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- November 30, 2019 2513
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--------------------- Saturday, November 30, 2019 --------------------
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