A NASA Spacecraft May Have Detected A Giant Wall At The Edge Of The Solar System
March 28, 2019
NASA‘s New Horizons spacecraft has helped scientists study a mysterious phenomenon at the edge of the Solar System, where particles from the Sun and interstellar space interact.\ This region, about 100 times further from the Sun than Earth, is where uncharged hydrogen atoms from interstellar space meet charged particles from our Sun. The latter extend out from our Sun in a bubble called the heliosphere.
At the point where the two interact, known as the heliopause, it’s thought there is a build-up of hydrogen from interstellar space. This creates a sort of “wall”, which scatters incoming ultraviolet light. About 30 years ago NASA’s Voyager 1 and 2 spacecraft first detected this wall, and now New Horizons has found new evidence for it. A paper describing its findings will be published in Geophysical Research Letters.
“We’re seeing the threshold between being in the solar neighborhood and being in the galaxy,” Dr Leslie Young from the Southwest Research Institute in Colorado, one of the co-authors on the paper, told Science News.
New Horizons made the detection using its Alice UV spectrometer, taking measurements from 2007 to 2017. It found an ultraviolet glow known as a Lyman-alpha line, which is made when solar particles hit hydrogen atoms. We see this ultraviolet glow all over the Solar System. But at the heliopause, there appears to be an additional source caused by the wall of hydrogen, creating a larger glow. Beyond the wall there’s more ultraviolet light compared to in front of it, suggesting it's being scattered by the wall.
"This distant source could be the signature of a wall of hydrogen, formed near where the interstellar wind encounters the solar wind," the researchers wrote in their paper.
The theory is not definitive yet. It’s possible that another source of ultraviolet light in our galaxy could be causing this background glow. To find out for sure, New Horizons will continue looking for the wall about twice a year. At some point, New Horizons will cross the wall, if it exists, so the amount of ultraviolet light it detects will decrease. That would provide some additional evidence that the wall is really there.
Voyager 1 and 2 are both past the wall now, so they’re unable to make any further detections. But New Horizons is only 42 times further from the Sun than Earth, a distance it has taken about 12 years to achieve, and is currently on its way to explore a new target called Ultima Thule having flown past Pluto in 2015.
If our estimates are correct, then by the time the mission ends in about 10 to 15 years, it should hopefully have just about made it to the wall. At that point, we might really know for sure if it’s there or not.
http://www.sci-techuniverse.com/2019/03/a-nasa-spacecraft-may-have-detected.html
太陽系邊緣有一堵神秘的「牆」！NASA飛船探測揭開太空玄機
2018-08-17
據外媒報道稱，近日來自美國宇航局（NASA）的科學家們相信他們通過NASA的新視野號探測器已經找到一項重要的證據——在太陽系的邊緣，有一道神秘的「牆」包圍着太陽系中的所有星體。
直到現在，當新視野號飛過冥王星飛往太陽系邊緣的時候，NASA的科學家們再度發現了這一現象——新視野號通過掃描紫外線來探測這一現象，發現了大量被困在我們恆星太陽風中的氫原子。科學家們認為，新視野號的發現足以作證前面旅行者號的發現，確認太陽系邊緣確實有一道「牆」，這神秘的屏障就像是太陽系與星際空間之間的邊界，並為太陽影響的邊緣提供了標記。
根據旅行者號的數據，宇宙射線在星際空間中的含量是地球附近的4倍，天文學家們提出了一個日光層的概念，這是一個特殊的像是氣泡一樣的層，將我們太陽系的空間區域囊括起來，並且作為輻射屏障屏蔽星際空間的輻射。
NASA的科學家在宣佈這一發現時寫表示，如果觀察到的紫外線不僅是太陽系內氫原子散射太陽光的結果，而且包括遠距離來源的實質性貢獻，那麼兩組數據都能得到最佳解釋。這個遙遠的來源可能是氫的「牆」的標誌，形成於星際風遇到太陽風的地方附近或可能更遠。
普林斯頓大學的太空科學家David McComas表示，如果這些數據能夠成功將太陽系周圍的氫「牆壁」完整的挖掘出來，那毫無疑問是一個令人興奮的發現。聖安東尼奧西南研究所的Randy Gladstone表示，大家還會將繼續尋找太陽系邊緣的這堵「牆」，預計從現在開始大約10到15年。研究人員表示，如果隨着新視野號的飛行，檢測到的紫外線水平變得急轉直下，研究人員說這可能證明已經離開了這道「牆」，就像旅行者飛出了太陽系那樣。
目前新視野號仍在向着太陽系邊緣飛行，預計將於2019年飛越Ultima Thule——這是已知的太陽系中最遙遠的星體。
https://kknews.cc/zh-mo/science/5o5nky3.html
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