Updated 1:51 p.m.
It was a threshold crossed in the deepest reaches of space: A spacecraft launched from Earth has now entered new and unexplored territory that may or may not be outside our solar system. A press release issued at 11:05 a.m. Wednesday morning by the American Geophysical Union noted that Voyager I had exited our solar system, sparking excitement in the scientific community.
But just a few hours later, the AGU stood down from its initial announcement that the 35-year-old craft had exited the solar system and instead clarified its location. The substance of the findings that precipitated the announcement remains the same, but the headline of the release has been changed, according to an e-mail the AGU sent out at 1:28 p.m.:
CORRECTED — Voyager 1 has entered a new region of space, sudden changes in cosmic rays indicate
NASA, which quickly denied the original report, sees nothing wrong with AGU’s science, merely how it phrased its findings. “The headline on the press release seemed to go beyond the study,” said Veronica MacGregor, spokeswoman for NASA’s Jet Propulsion Laboratory (JPL). But not all that far beyond: Voyager 1 has been at the frontier of the solar system for a long time, and unlike borders on the Earth—which are clearly drawn and, even in terms of sea and sky, have firmly fixed airspace and coastal limits—the official edge of the solar system is a mystery. NASA and the AGU agree that two recent discoveries about changes in the charged particles surrounding Voyager 1 put it at the very doorstep of interstellar space. JPL scientists are waiting for a third indicator, regarding the direction of magnetic lines, before they will officially announce that Elvis has indeed left the building. Said JPL in a statement released at 2:01 p.m. ET.
“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.”
What’s not in dispute among any of the scientists is that the spacecraft is now, undeniably, in a new and unexplored region—pushing the reach of humanity farther than it’s ever gone before. What we call that place is, in many respects, less important than the fact that we’re there at all.
Updates 1:15 PM
According to new scientific findings set for publication in the journal Geophysical Research Letters, Voyager I has pushed into the great unknown.
NASA, however, remains skeptical about these new conclusions. “Consensus of the mission team is that NASA’s Voyager spacecraft has not left the solar system,” a NASA social media specialist told TIME via e-mail. “Statement soon from NASA Jet Propulsion Laboratory.”
For years, scientists have speculated as to when Voyager would finally leave all traces of our sun behind — officially exiting the heliosphere, and entering the great undiscovered country beyond.
Two years ago, when TIME’s own Jeff Kluger penned his Voyager appreciation (34 years, still flying on — and on, and on), he reflected on the astonishing journey that the craft had taken — and the awesome boundary that lurked ahead: “There’s no way of knowing exactly where the solar system ends, but the best guess is that it’s up to 14 billion miles (23 billion km) from the sun,” Kluger wrote. “That’s where the last breaths of solar wind — the storm of charged particles the sun pours out all the time — bump up against the tenuous hydrogen and helium that swirl through the cosmos. Fourteen billion miles is about three times the maximum distance of Pluto (which was still a planet when the Voyagers were launched), so scientists always knew there would be a lot of flying to do before the ships crossed that threshold. That endgame, however, is approaching. Voyager 1 is currently about 11 billion miles (18 billion km) away; Voyager 2 trails a bit at 9 billion miles (14 billion km). In December of last year, Voyager 1 beamed back data showing that the charged particles around it appeared to have come to a standstill, suggesting that it had entered a final transition zone before interstellar space…”
Thirty-five years after its launch, Voyager 1 appears to have travelled beyond the influence of the Sun and exited the heliosphere, according to a new study appearing online today.
The heliosphere is a region of space dominated by the Sun and its wind of energetic particles, and which is thought to be enclosed, bubble-like, in the surrounding interstellar medium of gas and dust that pervades the Milky Way galaxy.
On August 25, 2012, NASA’s Voyager 1 spacecraft measured drastic changes in radiation levels, more than 11 billion miles from the Sun. Anomalous cosmic rays, which are cosmic rays trapped in the outer heliosphere, all but vanished, dropping to less than 1 percent of previous amounts. At the same time, galactic cosmic rays – cosmic radiation from outside of the solar system – spiked to levels not seen since Voyager’s launch, with intensities as much as twice previous levels.
The findings have been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.
“Within just a few days, the heliospheric intensity of trapped radiation decreased, and the cosmic ray intensity went up as you would expect if it exited the heliosphere,” said Bill Webber, professor emeritus of astronomy at New Mexico State University in Las Cruces. He calls this transition boundary the “heliocliff.”
In the GRL article, the authors state: “It appears that [Voyager 1] has exited the main solar modulation region, revealing [hydrogen] and [helium] spectra characteristic of those to be expected in the local interstellar medium.”
However, Webber notes, scientists are continuing to debate whether Voyager 1 has reached interstellar space or entered a separate, undefined region beyond the solar system.
“It’s outside the normal heliosphere, I would say that,” Webber said. “We’re in a new region. And everything we’re measuring is different and exciting.”
The work was funded by NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
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The original article has been updated to include an initial response from NASA.