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-------------------- 2525 - SUN - new discoveries with the solar probe
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- Also see Review 2489 about facts you won’t believe about the Sun. This Review is about some of the latest new discoveries.
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- The Parker Solar Probe’s intimate observations will untangle basic conundrums in solar physics and could help us better predict harmful solar outbursts aimed at Earth. Called coronal mass ejections, these dangerous clouds of extremely energetic particles produce shimmering auroras that can bedazzle even mid-latitude skies, but they can also knock out communication satellites, take down power grids, and could be lethal for astronauts.
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- Over its seven-year mission, the spacecraft will orbit the sun 24 times. Its trajectory also takes it close to the planet Venus. These flybys decrease the probe’s orbital speed and will ultimately allow it to sail within four million miles of the sun, or eight times closer than any previous spacecraft.
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- Solar-probe measures speed, density, and temperature of solar wind. Thermal shield Protects the probe from temperatures nearing 2500°F. The carbon-carbon composite shield is eight feet wide and just 4.5 inches thick.
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- Carrying four instruments, the spacecraft is flying through the sun’s corona, taking measurements of the solar atmosphere and trying to sniff out the origin of the solar wind, or clouds of speedy energetic particles that the sun endlessly exhales. Getting so close to the Sun is crucial, since the probe can sample the raw, pristine solar wind that we can’t easily study from Earth.
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- Already, scientists know that the gustier, supersonic breaths originate from cold, magnetic holes in the solar corona. But the denser, slower solar wind’s origin is a mystery. So, too, is the sun’s unfathomably hot atmosphere. While the star’s face burns at a relatively cool 10,000 degrees Fahrenheit, the upper corona burns at more than a million degrees.
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- The most stunning among the initial observations are dramatic magnetic waves that sweep through the solar atmosphere, instantly increasing wind speeds by as much as 300,000 miles an hour and, in some cases, causing a complete reversal of the local magnetic field.
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- During its first two passes, the Parker Solar Probe encountered maybe a thousand of these waves, which are mammoth locally but too small to detect from Earth. They last for seconds to minutes, would completely confuse a normal compass, and have no obvious source.
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- The team calls these features switchbacks, and some scientists suspect that if the waves are depositing energy, they could be playing a role in superheating the solar corona. But it’s not yet clear what is launching these kinks or if they will become stronger or more numerous as the spacecraft snuggles closer to the sun.
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- Also perplexing is the sideways speed of the solar wind. The Sun spins on its axis once every 24.5 Earth days, and as it spreads its barrage of particles initially rotates along with it. By the time the solar wind reaches Earth, it’s traveling radially, or streaming outward like water from a rotating lawn sprinkler.
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- When the Parker Solar Probe swung low over the sun’s southern hemisphere, it measured the solar wind’s rotational speed and found that the wind is whipping around the star much faster than anyone thought possible at such a distance.
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- Overly speedy winds can affect the rate at which stars evolve; newborn stars spin quickly and slow down over eons, losing energy in the form of these winds. While it’s not looking like our sun will burn out any faster than anticipated, these strangely fast winds hint that our star may slow its rotation rate more quickly as it ages.
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- The surprising rotational speed could also be affecting predictions about the trajectories and arrival times of coronal mass ejections, the solar spasms that can take out power on Earth.
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- As the mission continues, the Parker Solar Probe will undoubtedly reveal even more surprises. For one, the spacecraft is on the verge of detecting a long-hypothesized but never-seen area around the sun where it’s so intensely hot that “no dust can survive.” This dust-free area has evaded detection since its prediction in 1928 even during solar eclipses, when the near-sun environment is much easier to see from Earth.
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- And as the solar cycle begins to ramp up from its 11-year-minimum, scientists are expecting the mission to get even more exciting. Ultimately, the team hopes that the Parker Solar Probe will stare down the barrel of a monster coronal mass ejection, an event that will become increasingly more likely as the sun awakens from its slumber.
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- December 5, 2019 2525
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--------------------- Monday, December 16, 2019 --------------------
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