Artist concept of NASA’s Voyager spacecraft. Image credit: NASA/JPL-Caltech
For the better part of their journey since 1977, the two NASA spacecraft Voyager 1 and Voyager 2 have been the most distant human-made objects. Launched 16 days apart nearly 36 years ago, the two have seen and experienced space like nothing else that humans have created.
Now that Voyager 1 is on the verge of exiting our solar system, one gets some sense of how far the Empire of the Sun, which as stars go is a rather mediocre one, stretches. According to NASA, Voyager 1 is now 11.5 billion miles (Close to 19 billion kilometers) from the Sun. Traveling at 38,000 miles an hour after more than three and a half decades, it is still within the Sun’s domain or the “solar bubble” as scientists call it.
Just to give you some feel of how far that is, it takes radio signals traveling at the speed of light about 17 hours to reach at this distance. As the spacecraft gradually disengages from the solar bubble those signals will become fainter and one day they will be impossible to distinguish from the general radio noise emanating from the universe.
The primary reason for writing about Voyager 1 today is because there has been a bit of a controversy about whether spacecraft has indeed now left the solar system or still at the extreme outer reaches of it. It is amusing how even controversies among space scientists have such esoteric undertones whether a spacecraft has indeed entered interstellar (between stars) space or is still at the edge of the solar bubble.
Last evening, Wolf “Right Now” Blitzer said on his show on CNN that one of the stories coming up on The Situation Room was about Voyager 1 having left the solar system. Having followed the progress of these missions since my teenage I was naturally interested in such esoterica. I visited the NASA website to see what was going on and I found this brief statement on the spacecraft’s status update.
"The Voyager team is aware of reports today that NASA’s Voyager 1 has left the solar system," said Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena, Calif. "It is the consensus of the Voyager science team that Voyager 1 has not yet left the solar system or reached interstellar space. In December 2012, the Voyager science team reported that Voyager 1 is within a new region called ‘the magnetic highway’ where energetic particles changed dramatically. A change in the direction of the magnetic field is the last critical indicator of reaching interstellar space and that change of direction has not yet been observed."
As The New York Times’s Kenneth Chang reports today, the controversy arose following the publication of a paper late last year by two scientists in the journal Geophysical Review Letters said Voyager 1 had recorded a change in the mix of cosmic rays, which are high-speed charged particles. The reading indicated a near doubling of the particles, which mainly consist of protons, from outside our solar system. Perhaps it was tempting to suggest that the spacecraft had left the solar system, as indeed claimed yesterday by the American Geophysical Union which publishes the journal. NASA was compelled to issue the statement above because that was not its team’s determination.
The reason I used the word esoterica is because of the brilliantly detailed science at work in the explanations of these contradictory positions between NASA and the American Geophysical Union. NASA’s Dr. Stone has maintained, that it is a change in the direction of the magnetic field that would indicate that Voyager 1 had left our solar system and entered interstellar space and not cosmic rays. I don’t know about you but that makes perfect sense to me. If the spacecraft is still traveling under the influence its solar system’s magnetic field or as we scientists call it TUI-SOLMAG (A fake term invented by me), it would show a different direction. The orientation of the magnetic field in interstellar space ought to be different from ours because its source changes.
So there. It’s settled for now. As the Times says, the union sent out another email with a more accurate headline “Voyager 1 has entered a new region of space.” That is tantalizingly ambiguous.