Just a brief trip to outer space, before I post links to the next lengthy climate transcript. In the news this week, the people at NASA JPL announced (actually not – see my update!) that they believe Voyager 1 is about to leave the solar system, 35 years after its launch in 1977, and after having had thrilling close encounters with Jupiter and Saturn along the way. This being the vast wilderness of space, there is no obvious frontier which marks out the limits of the solar system, but the JPL people have picked up an increase in the amount of cosmic rays hitting the probe, which suggest it is crossing the borderland or “Heliosheath”, where the solar wind pushes up against the cosmic radiation from the rest of the universe, about 16 – 18 billion kilometres away.
What will happen to it now? And how long will we be able to keep in touch with it? The answer to the second question hinges on how much electrical power Voyager has access to, as it crosses the deep, dark gulf between worlds. The probe is powered by three RTGs (radioisotope thermoelectric generators) fuelled by plutonium-238, which of course is in limited supply and must be husbanded very carefully. And what it’s doing is gradually shutting down some of its more power-intensive activities in order to maintain others for as long as possible. That will last until about 2025, after which time the spacecraft will no longer be able to power any single instrument and Voyager will be drifting, inert and basically, dead.
I was curious to find out where it is heading. Anywhere famous, perhaps? There are actually two Voyagers, as you will know, and according to NASA Voyager 2 will pass within about 4.3 light years of Sirius, which is, of course, a very prominent and bright local star, well known to us from prehistoric times. This will take place around 296,000 years from now. Voyager 1, on the other hand, is heading towards AC+79 3888, otherwise known as Gliese 445, a very dim and unremarkable red dwarf in the unfashionable constellation of Cameleopardalis. It will pass by Gliese 445 in about 40,000 years, but what also might be surprising is that Gliese 445 itself is approaching the solar system much faster than Voyager 1 is moving in the other direction – it’s 17.6 light years away, at present, but will be only about 3.45 light years away from us, 400 centuries from now. Such is the unnervingly dynamic nature of stars, as they buzz like bees around the galactic hive.
So, what will happen to Voyagers 1 and 2, after that? Maybe they will drift forever in the dark spaces of the galaxy, until the end of time. Maybe one day humans will go out and retrieve them (or, even better, send a robot) and they will be exhibited in a museum, if they still have these in the 40th century (and I hope they will, as I think museums are a very good thing in any epoch.)
In the 1979 movie Star Trek: The Motion Picture, a Voyager probe has been discovered by sentient machines, who transform it into a gigantic and threatening spacecraft (renamed “V’ger”), which then starts to make its way back towards Earth and is only stopped by the brave people aboard the Enterprise, armed with their superior wits and sparkly late-1970s special effects. However, Trekkies will be aware that the probe in question was actually Voyager 6, and so the events of the movie clearly take place in an alternative timeline and dimension to this one, where I am writing this blog and where Voyagers 3, 4 5 and 6 were never built.
But maybe the basic premise of the film is correct, and someone – or something – else will find our little metal emissaries to the stars. And if they do, will it be good or bad news for Earth? I wonder.
Some interesting links:
NASA JPL’s main Voyager page: http://voyager.jpl.nasa.gov/
Interstellar mission overview: http://voyager.jpl.nasa.gov/mission/interstellar.html
Spacecraft lifetime: http://voyager.jpl.nasa.gov/spacecraft/spacecraftlife.html
After all that, I just realised that the NASA people haven’t actually made any official announcements yet. But they will, soon. Or they might do. Or something like that.