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Voyager 1 Reaches Interstellar Space
letxa2000 writes "CNN is reporting that Voyager 1, now some 8.4 billion miles (90 AUs) from the sun, has left the solar system and entered interstellar space by reaching the heliopause. However, whether the probe has reached the heliopause or is just coming close is the subject of two papers to be published in Thursday's Nature Magazine. The probe supposedly has enough nuclear fuel to last until 2020. Will it be able to find anything interesting outside the solar system in the next 17 years?"
Do you guys have any idea how much RAM had to be added to the Matrix to extend the simulation out that far?!
Kevin Fox
They've gone to plaid.
Life is the leading cause of death in America.
Heliopause
From Wikipedia, the free encyclopedia.
The heliopause is the boundary where our Sun's solar wind is stopped by the interstellar medium.
The solar wind blows a "bubble" in the interstellar medium (the rareified hydrogen and helium gas that permeates the galaxy). The point where the solar wind's strength is no longer great enough to push back the interstellar medium is known as the heliopause, and is often considered to be the outer "border" of the solar system.
The distance to the heliopause is not precisely known. It is probably much smaller on the side of the solar system facing the orbital motion through the galaxy. It may also vary depending on the current velocity of the solar wind and the local density of the interstellar medium. It is known to lie far outside the orbit of Pluto. The current mission of the Voyager 1 and 2 spacecraft is to find and study the heliopause.
An alternative definition is that the heliopause is the magnetopause between the solar system's magnetosphere and the galaxy's plasma currents.
Detailed answer: Yes.
Questions that can still be investigated by Voyager include a number of questions about the interaction between the solar wind, solar magnetic field, and interstellar medium, direct measurements of the interstellar magnetic field, the actual composition of interstellar gas, where exactly the heliopause lies, and how it's affected by changes in solar activity. I'm sure there are even more questions that I haven't thought of.
"They redundantly repeated themselves over and over again incessantly without end ad infinitum" -- ibid.
That's how long it takes a signal to reach us from the probe. When you consider the galaxy is 100,000 light years across, 8.4 billion miles is nothing.
Voyager uses a radioisotope thermoelectric generator for its power. This means that radioactive decay of its fuel creates heat, which is used to create power. That fuel's going to decay no matter what, so you either use the power or lose it.
I worked at JPL for the power group, so I can actually say something about this. All of the deep-space probes run on radiothermal generators. What this is basically a radioactive source surrounded by thermoelectric generators and alpha particle absorbers. Thus, both the thermal gradient established between the radioactive material and space (via heat pipes and radiators) and the alpha particles emitted by the radioactive material are able to generate power. There are two limitations on the lifetime of these generators - the lifetime of the radioactive isotope, and the durability of the thermoelectrics and alpha particle absorbers. I don't know too much about the particle absorbers, but I worked with the thermoelectrics, and there are durability runs of several years. However, Voyager is far older then any test we could ever do. My feeling in this is that barring high-heat conditions, the thermoelectrics should be able to last nearly indefinitely.
For many years I was a co-investigator on Voyager (actually, technically, I suppose that I still am; I have never been notified that the status ever changed). Anyway, the best guess when I was an active participant, throughout the 80s and half of the 90s, was more-or-less the year 2010. That was predicted to be the year at which the always-decreasing power output from the transmitter, the ever-increasing distance and the more-or-less constant sensitivity of the DSN (Deep Space Network) system combined to reduce the received signal to the point where it the bit rate at which information could be extracted was too low to be useful.
The general supposition was that funding would be eliminated before that date.
Voyager has been moving through space in ways unexplainable by physics. There is a small acceleration that can't be accounted for using known laws. It's almost like gravity doesn't work quite the way we think it does.
Of course, there is always the possibility that we just can't see the source of the acceleration, and it'll turn out to be something simple. However so far, all proposals put forth to explain it have been shown to be incorrect.
There is a deeper connection to very important issues in physics. For decades we have been studying the fabled "dark matter" which is supposed to be the cause of the anomalous rotation of the galaxy. The galaxy does not move in ways predicted by the laws of gravity. It is as if there is a huge amount of hidden mass which is influencing its rotation. So far we have not found any of this "dark matter."
But imagine the possibility. What if dark matter doesn't really exist? What if it's our understanding of gravity that is wrong? This would have profound implications throughout physics. After all our only direct experience of gravity is what happens here on Earth and within the bounds of the solar system. Except that today, we have a probe that has crossed that limit.
Perhaps the anomalous motion of Voyager will shed light on the situation. I for one would be utterly elated if it turns out we have to rewrite our physics books.
Voyager isn't useless yet!