Our an­gry star

The Sun in­ter­acts with the So­lar Sys­tem in many dif­fer­ent ways

All About Space - - Hole In The Sun -

mag­netic struc­tures than near the Earth. “In par­tic­u­lar, we be­lieve that the gamma-ray emis­sion is pro­duced sev­eral hun­dred kilo­me­tres deep within the Sun’s pho­to­sphere, which is a re­gion that’s par­tic­u­larly hard to probe,” Lin­den says.

Fi­nally, from the pho­to­sphere we go all the way out to the Sun’s ex­tended outer at­mos­phere, the corona, for the strangest fea­tures of all. The fact that the corona is up to 500-times hot­ter than the Sun’s sur­face isn’t new. The coro­nal heat­ing prob­lem has been known about since the 19th cen­tury, and many the­o­ries try to ex­plain it. The eerie-look­ing corona, which can be viewed from Earth dur­ing a to­tal so­lar eclipse, or by space­craft such as NASA's So­lar and He­lio­spheric Ob­ser­va­tory (SOHO), is a mil­lion-times dim­mer than the Sun’s sur­face, but be­cause Earth’s sur­face at­mos­phere is around two bil­lion bil­lion-times as dense – the corona be­ing up to only ten atoms per cu­bic cen­time­tre – there’s very lit­tle heat in the corona, despite its tem­per­a­ture.

What hasn't been known un­til now is that the Corona has a hid­den struc­ture. Dr Craig DeFor­est from the South­west Re­search In­sti­tute and his team ‘de­noised’ im­ages of the up­per, cooler parts of the so­lar corona us­ing NASA‘s So­lar Ter­res­trial Relations Ob­ser­va­tory (STEREO). He adds, “The work we did in­volves the corona at quite high al­ti­tudes, well above where most of the coro­nal heat is.” By look­ing at this re­gion the team un­cov­ered some­thing.

“By re­veal­ing that the outer corona is very highly struc­tured, we be­lieve we’ve found an en­ergy reser­voir large enough to ex­plain a re­lated heat­ing prob­lem – the so­lar wind heat­ing prob­lem.” The so­lar wind near the Earth can be be­tween 100,000 to 1,000,000 de­grees Cel­sius (180,032 to 1,800,032 de­grees Fahrenheit) when it should be closer to 2,500 de­grees Cel­sius (4,532 de­grees Fahrenheit). DeFor­est says that the most ex­cit­ing thing will be see­ing how this large-scale struc­ture will com­pare with the fine de­tail that will be mea­sured by NASA's Parker So­lar Probe, which launched on 12 Au­gust.

“We be­lieve we’ve found

an en­ergy reser­voir large enough to ex­plain a re­lated heat­ing prob­lem”

Craig DeFor­est

8. The outer boundsAt about 120-times the Earth-Sun dis­tance, the so­lar wind stops abruptly. De­tected by NASA’s Voy­ager 2 probe, this ter­mi­na­tion shock is con­sid­ered the start of in­ter­stel­lar space. 5. Shine bright like a flare So­lar flares are bursts of elec­tro­mag­netic ac­tiv­ity that may be ac­com­pa­nied by coro­nal mass ejec­tions. If one oc­curs in a coro­nal hole there’s noth­ing to stop the ma­te­rial fir­ing into space. 7. Cause a co­nun­drumAs the clos­est planet to theSun, Mer­cury’s or­bit can’t be ex­plained by New­ton’s physics. It takes Ein­stein's gen­eral the­ory of rel­a­tiv­ity to of­fer a so­lu­tion. 3. Man­gled mag­netic mix The Sun’s mag­netic field traps plasma, but can also con­tort un­til it ‘snaps’, send­ing charged ma­te­rial fly­ing into space as a coro­nal mass ejec­tion. This causes au­ro­rae.

6. WindsweptA con­stant stream of su­per­sonic, charged par­ti­cles from the corona – the so­lar wind – gives comets their tails, and once eroded away Mars's at­mos­phere. 2. Source of all lifeThe Sun, as a sta­ble source of heat and light, keeps Earth’s oceans liq­uid and makes the vast ma­jor­ity of life pos­si­ble (the ex­cep­tion be­ing life around deep sea vents). 1. Know your placeThe Sun’s heat ini­tially de­ter­mined what types of plan­ets formed and where. Rocky plan­ets like Earth are close by, while gaseous ones like Jupiter (made of volatile mol­e­cules) are more dis­tant. 4. There’s a hole in my out­er­most layerThin re­gions of the so­lar corona, with open mag­netic lines, look black in X-rays, look­ing like 'holes'. Th­ese coro­nal holes let ionised ma­te­rial stream out into space.

Data from Fermi showed an un­usual pat­tern of gamma-ray emis­sions pro­duced by the Sun

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