Voyager 1 has phoned in from the edge of the solar system to let us know what it's like out there. Now scientists are arguing over whether the 26-year-old spacecraft has really reached a telltale and important boundary.
Controversy is brewing over whether Voyager 1 has crossed the termination shock, a poorly understood envelope some 8.4 billion miles (13.5 billion kilometers) away, where supersonic particles from the Sun -- riding out on the so-called solar wind -- should slam into interstellar plasma and drop to subsonic speeds.
New Voyager data show something is up, but it's not clear what.
Astronomers expect the boundary to be somewhere between 85 and 120 astronomical units from the Sun (1 AU is the distance from Earth to the Sun). Launched in 1977, Voyager 1 is 90 AU from the Sun as of today -- farther from Earth than anything else that's ever left this world and well beyond the solar system's nine planets.
Voyager 1 will eventually pass the termination shock and, barring catastrophe, other expected boundaries. That will put the craft in interstellar space. Scientists are eager to learn as much as possible during this first trip through the edge of the solar system before the machine runs out of fuel in about the year 2020, rendering it unable to communicate.
Best New Blog finalist - 2003 Koufax Awards
A non-violent, counter-dominant, left-liberal, possibly charismatic, quasi anarcho-libertarian Quaker's take on politics, volleyball, and other esoterica.
Lo alecha ha-m'lacha ligmor, v'lo atah ben chorin l'hibateyl mimenah.