Heliopause
From Slackerpedia Galactica
Contents |
Definition
he-leo-paws NOUN The sorta kinda imaginary boundary when the solar wind of a given solar system becomes nigh indistinguishable from the other interstellar debris, dust, and atoms flying between stars.
Not a terribly useful term if you're just observing the night sky, but will become practical for cosmologists and the poor engineers who will have to confront the unprecedentedly beyond Herculean task of designing non-fictional spaceships that can deal with aforementioned solar winds, gamma radiation, cosmic rays, interstellar mishmash, dark matter, possible dark energy, and just about everything else, which is more intelligently referred to as the interstellar medium.
Theoretical Shape
This semi-theoretical semi-confirmed barrier is made more theoretical by the fact that it may be 100 AU to 200 AU since the heliopause's shape may in fact resemble that of a comet's tail, influenced here, by the Milky Way Galaxy's interstellar medium. Coupled with the Sun's relatively slow speed (A snail's pace of 250 kilometers per second, uh, relatively^), the actual size will probably fluctuate by as much as several dozen AU.
The general idea is that the big miasma of solar crap emanating from the Sun will culminate in a termination shock, somewhat like a tidal wave that begins to rise out of the ocean and crest3. In the case of the solar system, the area where this starts is called the heliosheath, something that will go lazily undefined. Now imagine this wave of "water" starting to get more massive and visible as the ocean depth decreases because the rocks start getting higher and higher. The proximity and size of the rocks cause the water to become larger and larger waves as it nears the beach. Following so far? Then SMACK! The ocean floor comes out onto the beach and the waves crash into land. Confused? Sorry about that.
Now imagine that the ocean is a three-dimensional sphere of water smacking not into land, but a gigantic current of OTHER liquid WHILE the "sphere" of water is moving at supersonic^^ speeds INTO this gigantic alien current. At this point, imagining a drop of water moving through a drop of water trillions of times larger that itself is hurtling through an empty vacuum propelled by other gigantic drops might be an apt visual analogy. But that's just more confusing, right? Sorry about that. Now imagine how the astronomers and cosmologists trying to solve this feel. (See Related Links for these suicidal people's websites.)
The "galactic wind shear" as well as the actual (or even approximate) locale of our heliopause will lend clues about how solar systems can successfully form and the role that both this confusin' barrier and Kuiper Belt Objects play in protecting life on a given inhabited planet, to say nothing of the implications when we start conquering, er, colonizing other solar systems.
Oort Clouds, Kuiper Belts, and Alpha Centauri! Oh my!
Whereas the Kuiper Belt is made of more meatier chunks of debris such as Pluto, Eris, and the more familiar comets and is closer (see Diagram 5), the Oort Cloud until recently has been composed of fairy dust. And not good fairy dust, scientific fairy dust. More recent efforts have finally yielded three potential candidates7. That's 3 maybes down and 3 billion to go The Oort Cloud's propensity for being as light-averse as dark matter or a vampire on PCP, its distance from our eyes, not to mention its distance from reality all present a wild card that may not be settled in relation to this big boring heliopause thing until we actually, to put it simply, get our keisters out there.
Real Observation?
As astronomy attempts to observe the puzzle away and cosmology tries to extrapolate it away, engineering may yet have the last nicotine-induced laugh. Specifically the ones at NASA. The four deep space probes sent out during the 70's (the 130 pound svelte Pioneer and more voluptous 360 pound Voyager twins) are at the cusp of encountering this inscrutable heliopause thing. In fact, the Voyager 1 probe has actually left the heliosphere (another one of these helio- words that means the space INSIDE the heliosheath, which itself is inside the heliopause).9 Put simply, Voyager 1 is now riding the wave hanging ten as it crests. This terminal shock will chuck Voyager 1 (Space porn plaque and all) into the heliopause by 2015.
No astronomer or cosmologist knows what happens when probe and shockwave meet heliopause. Three hundred pounds of scientific instruments (most of it when we measured processing speed in single digits) hitting the barrier should produce some kind of visible effect, assuming the creaky 38-year old's power system is still functioning in 2015. (The UV spectrometer already stopped in 2003 around the time it hit the heliosheath.^^^) The small amount of data already received will help paint a more dependable picture of our solar system's outer limits. The other 3 interstellar probes are a different story. Voyager 2 is not due for a full escape velocity outside the heliosphere, having not even breached the heliosheath. At a distance of 80 AU (20 AU behind its sibling), there is a more slim chance of meaningful data but one can hope.
Pioneer 10 and Pioneer 11 both stopped transmitting any real and substantive data by 2003 and 1995 respectively. The last hope rests with the fittingly named New Horizons probe recently launched. On a fast-track course to reach Jupiter in a year or less followed by the demoted Pluto, it is expected to be fully functional when it hits the heliopause around 2037. With preliminary data from Voyager 1 and follow-up details from the trailblazin' buffalo-shootin' New Horizons, a more realistic and pretty picture of the heliopause can be attained at long last.
Sources
1Seriously, why are you even clicking?
2Animated model of a heliopause
3Thanks to Wikipedia for the idea for this silly analogy
4That math
5Just click the link, kay?
6Havard and the British spoil the heliopause party
7Some possibly non-theoretical Oort Cloud objects
8NASA projection of interstellar probes
9Voyager 1 hits 100 (AU not age)
Related Links
University of Iowa's estimate at heliopause distance
A serious attempt to extrapolate heliosheath and heliopause distance
Attempts to the Kuiper Belt's outer limit
Heliopause movie just in case you missed the first time
Official Voyager Insterstellar Mission Webpage
Footnotes
^Compared to what, you're probably better off not knowin'.
^^Yes, we know supersonic doesn't matter in any atmosphere-lackin' medium. Stop editing it.
^^^It's unclear if the part failed or if it was shut down by NASA to cut costs at the time "this article hit press"
