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Back Opinion The Deep Voyaging


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GREETINGS everyone, I hope you were able to see the total lunar eclipse last Saturday night. It was spectacular!

And now, I’d like to take a little poll. I want you to think about the electronic equipment in your home. How old is your TV? How old is your computer? Your cell phone? Your DVD player? Now, try to figure out the age of the oldest piece of functioning electronic gear in your house.

I’ve got an ancient phone that’s probably 25 years old and that’s the oldest one for me. Does anyone have anything that’s 35 years old and still works?

Well, NASA does. In 1977, the Voyager space probes were launched and both of them are still working just fine, thank you very much, and they’re still returning astounding scientific data. After almost 35 years, they’re finally leaving the Sun. No, not just the solar system – the Sun.

It is perfectly true to say ALL the planets are inside the Sun because the Sun not only emits energy, it also emits particles. The solar system is embedded in a HUGE sphere of particles extending far beyond the orbit of Neptune (and Pluto!). It does eventually end, however, and where it ends is called the heliopause (literally translates as ‘Sun stop’).

Both the Voyages are poised just inside the heliopause and they’ve discovered strange and wonderful things (some of which I’ve talked about in this column). Now, for the first time, the Voyagers have detected Lyman alpha lines from our own Milky Way.

So what’s a Lyman alpha line? It’s a line that appears in a spectrograph showing where a hydrogen electron transitions from one particular energy level to another. We’ve seen lots of Doppler-shifted Lyman alpha lines generated by bright energy sources in other galaxies, but we can’t see the Milky Way’s Lyman alpha lines because our own Sun is so bright it drowns them out, just like city lights drown out all but the brightest stars.

So the Voyagers are now detecting two different kinds of Lyman alpha signals. Some come from those distant galaxies, and the other is from our own Milky Way – something we’re seeing for the very first time. The Lyman alpha signals from distant galaxies help astronomers understand how and when galaxies form.

The Voyagers are now in the heliosheath (just before the actual heliopause) and the Lyman alpha lines produced by the Milky Way are helping the astronomers generate a crude map of the actual edge of our Sun. The Voyagers are at that edge and they’re peering out into infinity.

Unfortunately, they won’t be able to do it forever. The Voyagers are powered by the radioactive decay of plutonium 238 and the Voyager astronomers estimate both spacecraft will run out of power somewhere around 2025. They no longer rotate the spaceships to conserve power and data are recorded from a fixed direction. But both spacecraft are still returning data and making new discoveries right now. How much 35-year-old electronic gear did you say you had that still worked?

I’m reminded of that quote by Sir Isaac Newton – you know, the one that goes: “I’m sitting on the beach playing with pebbles while the vast and undiscovered ocean of knowledge stretches before me.” Thanks to the Voyagers, we’re just beginning to enter that vast, undiscovered ocean.

Cruise on over to The Deep website at to learn more about space and many other topics. Enjoy!

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