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.
NASA Spacecraft Sees Giant Wall At Edge Of Solar System?
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.
Read more at www.iflscience.com
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jerry krause
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Hi John O’Sullivan (Editor of PSI),
Who is Jonathan O`Callaghan? The reason I ask is the curious mix of quotes and what appear to be non-quotes of information about this giant wall at the edge of the solar system in his posting.
There is a quote of a co-author of the paper (article) which is the focus of this posting. “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.
And then, without quotes I read: 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 th it’s being scattered by the wall.
Who is we? It seems ‘we’ must include Jonathan or, if ‘we’ is someone else, shouldn’t there have been quotes and an explanation of whom we are?
Just wondering what the journalist writing standards of PSI might be. Maybe you can clarify: “Beyond the wall there’s more ultraviolet light compared to in front of it”. Maybe I am nitpicking, but I am confused as to whether there is more ultraviolet light in the solar system than in the space beyond our solar system or if it is vice-versa or if at the wall there is more ultraviolet light than either in the solar system or in the space beyond the wall. I want to guess that it is the latter case but consider this does not really make sense because we ‘know’ that solar radiation is the source of the ultraviolet light within the solar system so I have to ask what is the source of the ultraviolet light of space. Now that I reason this far, I know the universe contains billions and billions of stars (suns) so these must be the source of the ultraviolet light of ‘space’. And this leads to a question: We (I) have outgoing ultraviolet light and incoming ultraviolet light and at the ‘wall’ where these two ultraviolet lights ‘meet’, should not there be a greater density of ultraviolet light?
I like to ponder to things and I know as a scientist i can never be absolutely certain. Of course, there are some cargo-cult scientists who believe they can be absolutely certain and they seem to consider that anyone who is uncertain must be mentally deficient.
Have a good day, Jerry
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jerry krause
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Hi John and Readers,
As I ponder Jonathan’s posting and its beginning I must admit it is very good introduction to the posting and that I had ignored the information of this introduction.
Particularly the statement: “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.”
There are very fundamental scientific ideas involved in this information which were not being considered by humans much more than 2000 years ago when some Greek philosophers began to consider that matter could be composed of tiny, individual, particles they termed atoms. But than for nearly 2000 years this idea was forgotten until mental midgets know as alchemists began doing experiments whose observed results forced the apparent conclusion that matter was composed of tiny, individual, particles they termed atoms. But before this happened these alchemists had done experiments whose results forced the conclusion that elemental matter was not air, water, earth, and fire. But elemental matter which was given names like hydrogen, oxygen, and carbon, to name just three of the more than 100 atoms of elemental matter now observed to exist.
After, the alchemists discovered by experimental results that elemental atoms of different tiny masses existed. The electrical nature of atoms and their internal structures had to be discovered by experiments (observations) of a community of scientists. That this discovery was a slow process is important because we can only imagine the tiny, tiny, tiny particles which are the composition of atoms.
The hydrogen atom is the atom of least mass. It is most commonly composed of a nucleus (one proton which has a positive electrical charge) and one electron (a negatively charged particle whose mass is about 1/1837th that of the proton. However, it is the electron which defines the volume occupied by the hydrogen atom even though the volumes of both proton and electron are very, very, very much less than the volume of the hydrogen atom.
Galileo and Newton, the founders what we today call physical science, probably imagined there were atoms but had no observable evidence of their existence. I doubt if either imagined these atoms might be composed of the charged electron and proton particles.
I review this fundamental background because I consider it is necessary to to begin to understand the information that Jonathan reviews in the remainder of his posting.
The central feature of this posting is: the ‘wall’. Which Jonathan precisely described (defined): “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. … 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.”
Here Jonathan introduces a fundamental physical phenomenon–scattering–which is not commonly considered at an elementary level of scientific understanding. So while the word scattering might be familiar; its explanation by physicists is not.
So I state without explanation that a charged hydrogen atom (which is actually a positive proton) cannot scatter radiation because it has no electrons but a uncharged hydrogen atom does and therefore can scatter ultraviolet radiation.
However, while Jonathan precisely define the ‘wall’ it is poor choice of a word because to most people a wall is a plane and not a volume of space.
I have written all these words to illustrate what a scientist must do as one ponders and attempts to understand (explain) the consequences of what maybe has been observed as one observes at the limits of one’s ability to observe.
Have a good day, Jerry
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Dan Morrow
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Thank you for the story links to NASA, fantastic stuff, great to see science in action, actually reaching and monitoring the edge of our solar system. I wonder what is on the other side?
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