Voyager 2 Detects Peculiar Solar System Edge 272
ClickOnThis writes "CNN reports that Voyager 2 has detected evidence of the magnetic edge of the solar system (aka the heliopause) at 76 AU (1 AU = 93 million miles), much closer to the Sun than the location of 85 AU found by Voyager 1. From the article: 'This implies that the heliosphere, a spherical bubble of charged low-energy particles created by our Sun's solar wind, is irregularly shaped, bulging in the northern hemisphere and pressed inward in the south. [...] The researchers think that the heliosphere's asymmetry might be due to a weak interstellar magnetic field pressing inward on the southern hemisphere.'"
Re:Er. Wait. (Score:5, Interesting)
The theoretical belief is that it should be relatively uniform, but it does not appear to be. Are 2 observations sufficient? No, but a difference in 9 AU in the 2 observations is significant in that it is far off the scall were it less than 1, or maybe only slightly different, that would better confirm the theory. If the physics say that it ought to be uniform, and observations shows that it isn't, th theory needs to be adjusted.
Re:Variable size? (Score:5, Interesting)
What variability? The sun is pretty constant on short time scales. The sun is being observed in detail by other spacecraft specifically designed for that task, like Helios. These spacecraft directly measure the solar wind and track the effects of solar. I'm sure the people at NASA have included that data into their analysis. They are rocket scientists, after all. The planets exert essentially zero influence over the heliosphere. So it's not like they have no idea about what's going without the Voyager data.
Re:Or perhaps... (Score:3, Interesting)
Unless the compression of the heliopause is on the leading edge relative to the sun's motion through the galaxy, this can be safely ruled out. This would also imply some hitherto undetected galactic medium causing a braking effect; surely any non-magnetic influence would affect solid matter as well, and cause the galaxy's rotation to slow over time (unless the medium rotates with the galaxy, in which case the motion of the medium relative to the sun is zero and braking should apply equally to all sides...the effect of motion again cancels out, so we're back to where we started).
perhaps extrasolar winds which remain undetected
Maybe, but without identifying a source of those winds its impossible to explain the uneven shape: what lies in that direction that could produce such a powerful effect? That's not to exlude the possibility, but it seems less likely than the weak magnetic field's influence, given what we do know about charged particles.
or the bubble is variable like the solar wind itself
That's probably true for small differences over time, but we're talking about an 11% variation. I'm no expert, but I'm pretty sure that any variation in solar activity that could cause that kind of change in the space of a few years would be detectable from observation. They probably considered this, checked, and found no link.
or maybe even gravitational tides due to the orbiting planets are influencing its shape.
On the plane of the elliptic where the planets magnetic fields and gravity have most influence that might make sense, but these are the polar regions; why would gravitational tides affect one pole one way, and the other pole the other way when the mass is distributed more or less evenly between them (gravity always pulls in, remember)? Besides, the particles involved already have the velocity to escape the sun's gravity, so even Jupiter's gravitational influence would have negligable effect. Its also known that charged particles are deflected by the Van Allen belt, while larger objects plow straight through because of gravity; magnetic fields are far more significant than gravity in this case.
there's so little to go on that a lot of rank speculation is required.
I'm not claiming we know everything (far from it), but we can use what we do know to eliminate what doesn't make sense. Put it this way: if I can point out the flaws with what you suggest with my meagre knowledge of astrophysics, the people who do it for a living are probably way ahead of both of us.
Perhaps a series of probes need to be sent out to the region of the Kuiper Belt to study the phenomenon more closely.
I agree with you 100% there. There is definitely someting interesting going on, but I suspect the explanation is more obvious than extraordinary.