Art by Brooke Muschott
The year was 1977. Disco music was groovy. It was actually cool to wear shiny polyester. Personal computers of any usefulness were only a few years away. And after years of planning, the Voyager 1 and 2 spacecraft were launched two weeks apart in August and September of that year aboard Titan-Centaur heavy-lift rockets. Together, these two spacecraft gave scientists and the public the first close-up pictures of the outer planets Jupiter, Saturn, Uranus and Neptune and their moons.
By 1989, the Voyagers had completed their primary mission: The exploration and imaging of the outer planets. They discovered the intricacies of Saturn’s rings, volcanoes on Jupiter’s moon Io, — imaged at the highest resolution of the time — the weather patterns on Jupiter and Saturn and so much more. Aboard each Voyager are three computers with a whopping 68 kilobytes total of memory. A digital camera produces image files that wouldn’t fit in the memory aboard the spacecraft. A modern computer may have 60,000 times more memory. The microprocessor speed of the Voyager computer is a blazing 250 kilohertz. My first computer in 1980 had a clock speed of 4 megahertz —16 times faster — and the computer on which this article is being authored is 3 gigahertz, or 12,000 times faster than Voyager’s computer. As a tribute to the genius of the scientists and engineers at the Jet Propulsion Laboratory (Pasadena, Calif.), they fit all of the guidance control, camera controls and data acquisition by the specialized instruments into those primitive computers.
But a greater testament to the design of the Voyager spacecraft is that those computers, launched into the hostile and inhospitable environment of space more than 35 years ago, are still operating. We can’t run the Windows operating system on a computer more than five years old, and many people replace their cell phones more often than their shoes. And these things we take for granted (including our shoes) are thousands of times more sophisticated than the computers aboard Voyager.
Twelve years after launch, Voyager’s computers are still working, and most of the instrumentation on board still operates. In fact, it is functioning so well that Voyager was remissioned to characterize the outer solar system to search for the heliopause boundary. The heliopause represents the outer limits of the sun’s magnetic field and outbound flow of the solar wind.
At more than 18 billion kilometers (11 billion miles) from the sun, Voyager 1 is now the farthest human-made object from the sun. This year, between April 9 and May 22, Voyager 1 left the confines of the solar system and is considered to be in interstellar space. Our indication that Voyager 1 has left the solar system comes, in part, with the difficult measurement of electrons in the space through which Voyager is passing. The measurements were made even more difficult with the failure of the plasma instrument in 1980, so all measurements were performed indirectly. For example, in one case, Voyager’s environment was determined by measuring the direction of the magnetic field produced by the sun in the space around the spacecraft.
The best solar models used by the Voyager science team suggested that there would be a dramatic change in the magnetic field direction as Voyager moved out of the solar magnetic field lines to those in interstellar space. Scientists also expected the levels of charged particles originating from inside the heliosphere to drop and the levels of galactic cosmic rays to jump.
On April 9, 2013, Voyager 1 detected disturbances in the magnetic field, a result of the St. Patrick’s Day solar storms 400 days earlier. The disturbances increased for more than a month and indicated that Voyager was moving into an increasingly dense region of plasma. This plasma had the signatures of interstellar plasma. Calculating backwards from the data, scientists report that Voyager 1 entered the interstellar medium around Aug. 25, 2012.
So, humans have sent something to the stars, eh? Well, maybe … not exactly … Ok, Sure. There is still that friendly controversy characteristic of many scientists and some confusion. Since the 1960s, most astronomers have said that the edge of our solar system is defined by the Oort Cloud, a cold, tenebrous bubble of gases and debris left over from the beginning of our solar system. Named after Dutch astronomer Jan Oort, the Oort cloud is thought to extend out to nearly a light year from the sun and may be the source of all long-period comets, like Halley’s Comet.
Some scientists don’t believe an object is really in interstellar space until the object is beyond the Oort Cloud. It will still take almost 300 years for Voyager to just arrive at the Oort Cloud and possibly 30,000 years to get through it. Since most of us won’t be around to see Voyager 1 leave the Oort Cloud, for the sake of a quiet life, most of us will just say over coffee that we are in interstellar space and move on.
Despite the long, varied and productive life of Voyager, it has only enough electrical power left to keep operating the instrument packages through about 2025. Voyager is currently traveling at more than 38,000 miles per hour and is aiming toward the stars in the constellation Ophiuchus. In the year 40,272 AD (give or take a few years), Voyager 1 will come within a couple light years of an obscure star in the constellation Ursa Minor (the Little Bear) called AC+79 3888, and our sun will be nothing but a nearly invisible spark of light in a star field of millions of stars.
For now, Voyager 1 belongs to us. Soon, Voyager will belong to the Milky Way Galaxy.
As published in the Oct. 24, 2013 issue of the Pepperdine Graphic.
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