All About Space - - The Impossible Star -

It may be one of the most fa­mil­iar ob­jects in the sky, but there is a per­sis­tent mys­tery sur­round­ing our Sun: why is its outer layer so hot?

If you start in the core of our star and work out­wards through it lay­ers, the tem­per­a­ture con­tin­ues to drop through the ra­dia­tive zone and con­vec­tive zone, out through its vis­i­ble sur­face, the pho­to­sphere, to the dark­ness of space. But that’s where things get weird. The pho­to­sphere has a tem­per­a­ture of around 6,000 de­grees Cel­sius (10,832 de­grees Fahren­heit), but by the time you reach the corona – the Sun’s ten­u­ous outer layer – it climbs again to sev­eral mil­lion de­grees. This coronal heat­ing prob­lem has stumped astronomers for decades, and they’re des­per­ate for an­swers.

The re­cently launched Parker So­lar Probe could well help, as it will fly closer to the Sun that any mis­sion be­fore it. Liv­ing up close and per­sonal with the corona could fi­nally tell us why things don’t con­tinue to cool the fur­ther you move from the core, the source of the Sun’s im­mense power.

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