We’re going far out into space for this next conversation, beyond what’s called the heliosphere. That’s the protective bubble that the sun creates by giving off something called solar wind. To give you an idea of how big the heliosphere is—it extends beyond Pluto. NASA’s Voyager 1 broke through the heliosphere a few years ago, but the magnetic field data that it gathered didn’t match what scientists expected to find.
A UNH-led study now explains the gap between what scientists expected and what they actually saw. David Brooks, a reporter with the Concord Monitor and writer at GraniteGeek.org, spoke with NHPR's Peter Biello about what they found.
So let’s start back in mid-2012. What happens with NASA’s Voyager 1 at that point?
Well, Voyager 1 had been tooting along since it was launched in 1977. In fact, it’s 38th anniversary of its launch is on Thursday. It’s been gathering measurements, and scientists have been waiting for it to get to the heliosphere, which, as you mentioned, is sort of the huge bubble around the sun that’s caused by charged particles that the sun emits. It’s got all that energy—so much energy that it tears atoms apart and sends actual particles, electrons and protons, out into space, all on their own. It’s called plasma. It doesn’t send very many of them because of course space is mostly empty, but it sends almost 2 billion kilograms of weight in subatomic particles per second, so there’s a lot of these things out there.
Voyager 1, as well as its twin, Voyager 2, have been gathering data about this, waiting for the time when it got to the point where it was far enough away from the sun that it was no longer really feeling the effect of the solar wind, these charged particles, and instead would start feeling the effect of the charged particles that are floating around outside the solar system produced by other stars. Of course there are even fewer of those, because space is really empty outside our solar system, so there was a lot of excitement about when it’s going to get to the heliopause, which is the skin of the bubble of the heliosphere.
And the scientists expected something to happen when Voyager 1 passed through that barrier. What did they expect?
This, I believe, is dumbing it down for us layman, but they talk about the magnetic field and they act like it’s a compass, but it’s not a compass like you and I use when we’re out in the White Mountains. It’s measurements that say, what direction the particles that are encountering the craft, what direction they’re coming from.
They basically expected it to spin from pointing at the sun to pointing away from the sun, roughly. And it didn’t. As a result, there was an announcement in 2012—you may have remembered this—Voyager one was the first craft to leave the solar system. Then NASA said—wait a minute. They were waiting for the data, it’s got 38 year old technology, and there are problems with the measurements, so we’re not sure it actually has. So there’s been an argument about it for several years. This most recent research, which comes out of UNH Institute for Earth, Oceans, and Space, looked at data from several other spacecraft, notably IBEX, and they sort of triangulated it, the data from all those, and said that, yes, Voyager 1 actually passed into the heliopause, the edge of the bubble, was leaving the bubble around the sun, and the reason that the readings were not what were expected was that there were anomalies in the field. It’s not just a big specherical field of plasma around the sun, but it has anomalies, and Voyager 1 happened to go through anomalies, and that’s what caused the compass readings to be different from expected.
For space geeks, David, this seems really exciting—to finally learn about what it’s like to be beyond the heliosphere.
Exciting isn’t the word! I put this on the Granite Geek blog and it has gotten more than ten times the traffic of any other post I’ve put on the blog since I came on the Monitor, to the point where our IT guy sent me a note and said, “Well done!” But all I did was cut and paste the press release from the UNH news service.
But there was considerable discussion in the post about how long the instruments will continue reading on Voyager 1 and Voyager 2. Their system is based on plutonium, on radioactive decay, so they’re expected to make readings and send them back in dribs and drabs for a couple of decades more, which is kind of interesting.
I have to admit that the startling thing about this is that it tells us how enormous space is. Voyager 1 has been going for many tens of thousands of miles an hour since 1977, since the Carter Administration, and it’s been charging along at this staggering speed, and it’s only just now outside the solar system, and the distance to the next star is just orders of magnitude greater. So all these science fiction stories about zipping to the stars really puts it into perspective.
So maybe we’ll now discover the secrets to the origins of the universe?
I prefer to think that we’ll encounter little green men who have been waiting around outside Pluto for us to get them, and they’ll say, “Hooray, welcome to the universe!”