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NASA's Solar Probe Plus mission is moving ahead with its daring 2018 launch to study the sun's super-heated atmosphere.
The surface of the sun is almost 10,000 degrees Fahrenheit. That’s really hot. But the sun’s corona is over 200 times hotter—millions of degrees Fahrenheit. That’s like the actual flame of a fire being 200 times colder than the air around that fire.
Why would the area around a hot burning mass be hotter than something that is actually closer to the source of heat? And if the corona is so hot, then why doesn’t it heat up the sun’s surface to a similar temperature?
Well, the truth is that nobody knows for sure.
I wonder how close it can come to the sun before evaporating .
Solar Probe Plus will study the streams of charged particles the Sun hurls into space from a vantage point where the processes that heat the corona and produce solar wind actually occur. At closest approach Solar Probe Plus will zip past the Sun at 125 miles per second, protected by a carbon-composite heat shield that must withstand up to 2,500 degrees Fahrenheit and survive blasts of radiation and energized dust at levels not experienced by any previous spacecraft.
APL is designing and will build the spacecraft, on a schedule to launch no later than 2018. The compact, solar-powered probe would weigh about 1,350 pounds; preliminary designs include an 8-foot-diameter, 4.5-inch-thick, carbon-carbon carbon foam solar shield atop the spacecraft body. The solar arrays will retract and extend as the spacecraft swings toward or away from the Sun during several loops around the inner solar system, making sure the panels stay at proper temperatures and power levels. At its closest passes the spacecraft must survive solar intensity more than 500 times what spacecraft experience while orbiting Earth. Solar Probe Plus will use seven Venus flybys over nearly seven years to gradually shrink its orbit around the Sun, coming as close as 3.7 million miles (5.9 million kilometers) to the Sun, well within the orbit of Mercury and about eight times closer than any spacecraft has come before.
Good use of the ol' Noggin "TrueBrit" you may be on to something there!
originally posted by: TrueBrit
a reply to: swanne
Something strikes me. The Suns gravity and electromagnetism are less strongly felt, the further one tends to be from the sun, correct? Could it be, therefore, that the corona is hotter than the surface, because the corona is further from the centre of these crushingly powerful forces, meaning that particles in the corona are free to move around at a much higher speed, resulting in a much higher temperature, than particles closer to, or on the surface of the sun, which are compressed by magnetism and gravity far more strongly, slowing them down some?
Solar Probe Plus will use seven Venus flybys over nearly seven years to gradually shrink its orbit around the Sun, coming as close as 3.7 million miles (5.9 million kilometers) to the Sun,