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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?"
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.
NASA's page on the heliosphere
Dogma - "let's just say we'd like to avoid any empirical entanglements."
actually, kinda... it's the sound of a deep bass, which the human ear can't hear... they found out because they noticed it shifted planets and stars along it's wave... check it out here: space.com
What's the range of communications for the probe? When will we lose our connection (if we haven't already)?
No one knows for certain. A number of factors enter in, including the ability of Voyager to keep its antenna pointed at Earth, the amount of power left in the radiothermal generator, the size of radio telescope available for communicating with it on Earth, and possibly unknown effects from the heliopause.
"They redundantly repeated themselves over and over again incessantly without end ad infinitum" -- ibid.
90 AUs (Distance from the Sun to the Earth)
*
8 minutes (Time it takes light to reach Earth from the Sun)
=
720 Light Minutes
/
60
=
12 Light Hours.
We're quite a ways away from the Light Year.
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.
The fuel is for communicating, not for moving.
There's no friction in space. It can travel forever in its current direction. When the fuel runs out in 2020, we won't be able to hear from it.
There are no trails. There are no trees out here.
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.
(going from water to air is a speed increase, and I'm guessing its some function of density)
That's backward, sound travels much faster through water than through air. It does relate to density but not directly. The quantities that influence the speed of sound are the temperature and something called "bulk modulus" which describes how the material density changes as the pressure changes. Temperature is more important at very low densities. At higher densities as in solids the bulk modulus is the primary factor.
The spacecraft in question wasn't Voyager, but PIONEER 10. My point stands however, that having probes in the far reaches of space away from the solar system will be extremely valuable in the study of theories of gravity. Here's a link to a good place to start. A good Google search is "pioneer anomalous acceleration"
Near the end of the article I linked, they explain that this effect is not observed with Voyager because of the way Voyager is stabilized by boosters (as opposed to spin-stabilization for Pioneer). If the effect is occurring with Voyager it is completely swamped by the booster accelerations. They also indicate that (obviously) the best way to continue studying this is to launch another probe outside of the solar system.
If you spend any time researching this, you'll find groups of people all over the place who claim to have explained it. But none of them agree with each other. I think it's accurate to say that nobody REALLY knows what's happening.