I teach high school math and science, and I have shown this graph to students every year. Many students get what this really means. They suddenly understand how far Voyager is from us, and how small and isolated our solar system really is in the universe.
Now it will be fun to show them the same graph from Voyager 2 !
Your Voyager 1 graph [footnote 0, in the parent comment] shows two periods of particles-per-second drops to around 10 particles per second followed by a rebound and then a dramatic drop to 2 to 3 particles per second.
The Voyager 2 graph [footnote 2, in the parent comment] shows a single drop to around 17 to 18 particles per second and what looks like the beginning of a rebound. Wouldn't interstellar space be characterized by the drop to below 3 particles per second?
Is this the same issue we had with Voyager 1 where Voyager 2 is beginning the process of entering interstellar space but has not yet actually entered it? If not, why are the particle counts about an order-of-magnitude higher for Voyager 2 then they were for Voyager 1 in interstellar space?
In early November, the team noticed a sharp decline in the number of particles, but not to zero. This means that the spacecraft still has a long way to go until scientists can declare it free from the solar system.
Due to the fact that the power of the Sun rises and decreases, the position of the heliopause is not constant. Therefore, it is impossible to say exactly when Voyager 2 will leave the Solar System.
So your interpretation is correct, Voyager 2 is approaching the boundary, but hasn't yet definitively crossed into interstellar space. The phrase 'leaves the Solar System' is misleading, depending on your interpretation of where it ends. We can probably expect a few more confused articles announcing this in the next few months until it is certain.
Better detector? Those are detected particle counts
It's worth noting that  uses a non-zero baseline value, so the actual difference between the top of the plot and the bottom isn't nearly as pronounced as the difference shown in .
There is a relatively sharp transition— the Heliopause— from solar wind dominating to interstellar “wind” (from other stars) dominating, which occurs where their respective radiation pressures are roughly equal:
The specific dynamics of the cloud (e.g., its turbulence) are still largely unknown, though the fact that the direction of intersellar wind has shifted by several degrees over a few decades hints that it’s not totally calm.
I’m not sure about solar sails outside the heliosphere... that’s an interesting question. I’m not an expert, just a guy who likes reading about this stuff.
What I'm trying to say is that if you are trying to show that voyager's surrounding environment suddenly changed, this is the worst possible chart to use. If the gradient was perfectly linear, you would still see sudden drop at some point, depending on which random threshold you choose.
I was assuming the "0.5 MeV/nuc ions" just meant they are counting all nucleons they encounter with at least that much (kinetic?) energy. I don't see how your interpretation works with that, but I could very easily be missing something.
My naive interpretation is that the graph does a great job of demonstrating the environmental change.
Also, looking at the voyager-1 data I would expect that voyager-2 is not yet out. The rate for voyager-2 only dropped to ~17 particles/sec which is more similar to the "false starts" seen in the voyager-1 data. From the article I got the impression these dips are only seen right at the heliopause.
Pirate Bay? Hmm...
So it seems @eecc was correct about at least the "PBS? Not available due to rights restrictions." part.
I guess the actual thresholds crossed are different but at this point who cares, unless you actually know those thresholds. It's out there and getting farther out. Yay.
If you can't describe an achievement without sensationalizing the hell out of it for the Nth time, maybe don't describe it.
Here's a video of what it takes "simply" to get out near Jupiter, nevermind out of the solar system.
The Voyager spacecraft took advantage of a special planetary alignment that won't happen again for over a hundred years.
Having said that, if by 'spacecraft' you mean something weighing a few grams, the Starshot program might be able to obliterate the Voyager records.
wow... that's not very efficient...
Well that’s unusual isn’t it? Perhaps there was a temporary issue/delay with #1? I didn’t see the explanation in the article.
Do you know this or are you speculating?
> Two trajectories were selected. One was designated JST: its mission would take it to Jupiter, Saturn, and Titan, with the probe's trajectory designed to optimize the Titan flyby. The second was designated JSX: it would be launched on a trajectory that would preserve the option of a Grand Tour, while serving as backup for the first probe. It would arrive after JST, and if JST were successful, it could continue with the Grand Tour. If JST was unsuccessful, JSX could be diverted to perform the Titan flyby itself, which would eliminate the possibility of a Grand Tour.
> The two spacecraft that launched retained the same mission concept. Voyager 1's course was optimized for the Titan flyby and Voyager 2 for the Grand Tour. Voyager 2 would reach Saturn nine months after Voyager 1, giving plenty of time to decide if it should proceed with the Grand Tour. Additionally, by launching Voyager 2 first, Voyager 1's launch could be re-targeted to perform the Grand Tour if Voyager 2 were lost in a launch failure. An option to skip Voyager 1's Titan flyby and proceed from Saturn to Pluto was identified, though Titan was still considered the more interesting target, especially after images from Pioneer 11 indicated a very substantial atmosphere.
> With Voyager 1's mission complete, Voyager 2 was cleared for an extended mission to Uranus and Neptune, fulfilling the goal of a Grand Tour as proposed in 1964.
Direction + a large enough receiver on Earth. Oh, and lots of error correction.
The probes use a star tracker to determine their orientation (they apparently look for the sun and one other star). I assume they keep track of their expected position in the solar system, and this is fine-tuned with updates from the ground station. If you have position and orientation, you can compute where the Earth should be at the current time and point the antenna in that direction.
"the US space agency says that Voyager 2 has a working instrument aboard that will provide "first-of-its-kind observations of the nature of this gateway into interstellar space"."
Does anyone know what Voyager 2 is carrying that Voyager 1 wasn't that might give interesting data in this part of space?
Getting humans into Mars to study Mars geology is priority. Once humans have been in Mars few times and the public interest vanishes–as it did during moon missions–there may be more money for telescopes and probes and cheaper robotic exploration.
53 million households in the US (over 580 million globally) watched the Apollo 11. The numbers dropped dramatically after the first mission. Apollo 13 was dramatic exception. People get bored easily and lose intrest.
If I would have a say, the priority should be the Overwhelmingly Large Telescope (OLT). US and other countries should have joined with Europeans to make it happen. The cost was 'just' 1.5 billion. Europeans opted for Extremely Large Telescope (ELT) instead and US is dong thirty meter telsecope. OLT would have been really something.
but, it's cool that it will continue transmitting until about 2027!
But think about this, we say we left Earth for space when we actually leave Earth's atmosphere. When you cross heliopause you are actually leaving "atmosphere" of solar system. Within it it is dominated by the particles from solar wind. And the change is very abrupt and well defined (but only in the direction of the motion of the Solar system, ie. where Voyagers are) in contrast to how Earth's atmosphere just gradually thins out and we have to get into some sort of agreement when it actually ends.