Have humans ventured, for the very first time, into the vast unknown of interstellar space?

The Voyager 1 probe is now more than 11 billion miles from Earth, or 120 times the distance between Earth and the Sun. No man-made object is further away.

Now there is tantalizing evidence the probe has officially exited the solar system. This point is known as the heliopause, the point at which the Sun’s solar wind — such as magnetic fields, energetic particles, solar wind plasm — is stopped by interstellar space.

Nick Suntzeff, a Texas A&M astronomer, forwarded me the following link, which measures the number of energetic particles, primarily protons, encountered by the spacecraft as it moves through mostly empty space.

What’s important about this is that such particles are also a good proxy for cosmic rays, and it appears that Voyager is measuring an increase in cosmic rays.

“This probably means that Voyager 1 has left the solar system officially, in that it is no longer protected by the solar magnetic field, and is now totally open to whatever space throws at it,” Suntzeff said. “It is fascinating result which I have not seen reported anywhere.”

I agree that it’s fascinating, and now it is indeed reported.