For several years your tracker has ranted relentlessly and tediously about reporters who, writing fast and thinking slow, have declared that the far-roaming spacecraft Voyager 1 either has or has not yet left the solar system. Here is one of the longer samplings of my bile.
The broaders news has been real. Media for quite awhile have responded to scientific debate whether the craft, launched in late summer 1977, had soared clear of the Sun’s thin “heliosphere,” the (utterly non-spherical) bubble of outward-pressing, weakening solar wind and entered the vast interstellar medium with its distinct electric and magnetic forces and particles. The common overexcited, hasty mistake was to report that the boundary, the heliosheath, is the edge of the solar system. Since every decent definition of the solar system includes comets, many of which are in orbits far more distant than is Voyager 1 or its close-following sibling Voyager 2, they shall therefore remain in the solar system for many human lifetimes yet to come.
Well! I dunno if it is cause and effect but this particular fever spell of science- journalism-blindness-to-space-borders appears to have broken. Exhibit A:
- Space.com – Mike Wall: Confirmed: Voyager 1 in Interstellar Space ;
Wall’s passages that put salve upon my sore point: Interstellar space begins where the heliosphere ends. But by some measures, Voyager 1 remains inside the solar system, which is surrounded by a shell of comets known as the Oort Cloud. While it’s unclear exactly how far away from Earth the Oort Cloud lies, Voyager 1 won’t get there for quite a while. NASA scientists have estimated that Voyager 1 will emerge from the Oort Cloud in 14,000 to 28,000 years.
Well about time, even if Wall did hedge the point in the “by some measures” line. Actually, the gist has been reported by others. But this one crossed my eyes this morning and revved my motor. The fascinating science behind the news has been coming in episodes. As I understand things about the key clue from Wall’s well-done piece, the density of the expanding solar wind as it poops out falls below that of the interstellar medium into which it is pushing. The denser stuff transmits trains of shock waves at a higher speed – meaning their frequency goes up. A big source of shockwaves spreading up through the heliosphere and beyond is big eruptions on the sun. Scientists receiving Voyager 1’s faint signals say they now have seen three such events in the last year or two. The last showed particularly clearly that the vibrations swept past Voyager 1 at the higher frequency expected if it is in the interstellar medium. QED, thrice.
The change in journalistic borderland terminology for the solar system has been gradual. Last year, at another outlet, came a piece from a first-rate astronomy writer who described properly the problem with saying Voyager 1 is leaving the solar system. She also got in the reason why the answer to any logical-thinking person (i.e. me) is no, it’s not.
- Universe Today (Sept 12, 2013) Nancy Atkinson: It’s Official: Voyager 1 Is Now In Interstellar Space ; Good description of the gadgetry on the probe that – with other more suitable instruments pooped out – delivered the information about how fast shock waves were moving past it. Atkinson’s story went back and forth a bit on whether entering the interstellar medium (or interstellar space) is the same as leaving the solar system. But the story explicitly declares that the more-distant comets of the Oort cloud are in the solar system.
NASA’s announcement got other pickup:
- Universe Today – Elizabeth Howell: Voyager 1 Hears Sun Echoes Far Away, In Interstellar Space ; As did Wall’s piece, this report includes a phrase particularly pleasing to this beating heart: “NASA’s announcement in 2013 that Voyager 1 is in interstellar space was accompanied by intense discussion about whether it is in or out of the Solar System (it still hasn’t reached the shell of the Oort Cloud that hosts comets, a milestone that won’t be possible for 300 years)
- CNET – Michael Franco: NASA’s Voyager 1 hit by third solar ‘tsunami’ ; Here is one, little mistake (one I have made too). It is Voyager 1, not Voyager I as in the capital letter i. Franco also keeps a flicker of the solar-system-exit habit alive further along, writing the “Still, Voyager is not quite out of our solar system, as it has one final ring of comets to penetrate before it can claim that distinction.” Not quite? Not close. It might reach it in a few centuries. The other side is thousands of years off. Includes digital recording of the crucial signal, converted to noise.
- The Weather Network – Scott Sutherland: Solar ‘tsunami wave’ helps confirm that Voyager 1 is in interstellar space ;
Grist for the Mill: NASA Jet Propulsion Laboratory Press Release ; Which also makes very clear that this is a historic event in space, but the machine is still within the solar system’s border, a murky and inexact place where solar orbits become unstable against the influence of other stars’ gravity.
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