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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.
Not much really. Neither the probe nor the space it "travels through" actually required any simulation at all. We only needed to simulate the probe's signal back to earth, and the data it "generated", which was merely made up from preconceived expecations, anyway. The humans were happy, and all is right with the world.
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.
Isn't that spiff? :-)
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.
... expensive.
The Voyager probes weren't built for speed. They were coasters, zipping from gravity well to gravity well with just a few puffs from the steering jets now and then.
If there were some pressing reason to catch up, we could do it, although it would be pricey due to the current high cost of getting things into orbit. You'd need to get something up there with a motor capable of adding substantial change in velocity. A big liquid fueled motor, or perhaps one of those new-fangled ion drives powered by a really big solar collector or a small reactor.
This is one of those problems that will get easier with time, assuming even modest progress in space propulsion. If we ever get practical fusion drives (theoretical of Isp topping 100,000 seconds!) we could get out there in a couple of years.
Stefan
Stefan
Read more...
'Go for the eyes, Boo, go for the eyes, aaarrrrrrrr!' -- Minsc
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.
What is this fuel used for? Just for communicating, or does it still need acceleration? If it's just for communication, couldn't they make it last longer by increasing the intervals between each time it communicates?
I believe they are talking about the nuclear battery that's onboard to power it's 20watt transmitter. Near as I remember the decay of plutonium causes heat which keeps the craft warm and operational, and is used to generate power. Given that this was launched in 1978, this is a major accompishment.
There is no sanctuary. There is no sanctuary. SHUT UP! There is no shut up. There is no shut up.
Why is it that we can brainwash the masses into thinking that it's okay for us to spend billions on space crap while ignoring the homeless people living in the streets and at the YMCA?
You are very shortsighted. Funding technology research creates new solutions to age-old problems. One day, a technology will be invented that makes hunger obselete (as in the Star Trek future). This technology is only limited by will, means, and time.
Simply giving the money to the poor solves nothing. So they can buy pizza for their kids tonight. Big deal. It does nothing towards their ability to get pizza tomorrow or the next day.
This is why direct social programs are a waste of tax payers' money. They make the politicians feel good about themselves while saving them from having to think about real solutions that hit problems at their foundation. Socialized healthcare is an excellent example, where there are real government-caused problems that prevent the health care market from functioning, so the politicians take the easy road and create a socialized system that steals people's money against their will putting it into a bureaucracy that will kill more people than it helps.
Healthcare article at Kuro5hin
So, a supersonic velocity means the space probe is moving faster than the mean speed of the errant hydrogen atoms.
Subsonic means it's moving slower than the mean speed of the atoms, and a wave can propagate ahead of it.
In this case, the velocity of the particles from the sun slows down when they encounter interstellar particles.
from-JPL.NASA "The solar system does not end at the orbit of Pluto, the ninth planet. Nor does it end at the heliopause boundary, where the solar wind can no longer continue to expand outward against the interstellar wind. It extends over a thousand times farther out where a swarm of small cometary nuclei, termed Oort's Cloud, is barely held in orbit by the Sun's gravity, feeble at such a great distance. Voyager 1 passed above the orbit of Pluto in May 1988, and Voyager 2 will pass beneath Pluto's orbit in august 1990. But even at speeds of over 35,000 mph, it will take nearly 20,000 years for the Voyagers to reach the middle of the comet swarm, and possibly twice this long for them to pass the outer boundaries of cometary space. By this time, they will have traveled a distance of two light-years, equivalent to half of the distance to Proxima Centauri, the nearest star. "
Dunno what CPU?
(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.
Never trust the mainstream media to get a science story right!
r .html
Voyager 1 *might* have reached the Termination Shock--NOT the heliopause. The termination shock is where the solar wind--electrically charged (ionized) hydrogen atoms blown off the surface of the sun--slows from 700,000-1.5 million miles per hour, down to under 250,000 mph. This indicates it's getting nearer to interstellar space because the solar wind is getting weaker, and it's having more trouble pushing against the interstellar winds of the galaxy. The termination shock lies somewhere between 80 and 100 AU. Between the termination shock and the heliopause (the true edge of the solar system), is the "heliosheath" region--kind of the Siberia of our solar system (distant, cold, dark). The heliopause lies around 120-150 AU.
In effect, Voyager 1 may have reached the outtermost region of our solar system (which no craft has ever done before), but it still has 10-20 years to go to reach interstellar space. Here's NASA's press release. Note they say Voyager is about to reach the solar system's final frontier--not the edge of the solar system:
http://www.gsfc.nasa.gov/topstory/2003/1105voyage
for more, see Discover on tweaking the theory of gravity, and Sky & Telescope on evidence against it.
Any references I can read? astro-ph will do fine... :-)
Oh yes, there are many detections of massive astrophysical compact halo objects in our galaxy, P. Popowski et al, and there is also a lot of work going on to use the same ideas to look for similar bodies in other galaxies. In fact, the microlensing ideas were first proposed for extragalactic studies by Chang and Refsdal in an article in Nature in 1979. The funny thing about this is that it doesn't matter what kind of matter it is, as long as it is gravitating. Also, it is easier if it is clumped, but it doesn't need to be.
Shameless plug: My thesis: Gravitational Microlensing of Quasar Clouds: Detectability in a Worst-Case Scenario.
Would be cool!Employee of Inrupt, Project Release Manager and Community Manager for Solid