<p>"This is a very exciting time, said Voyager project scientist Edward Stone. "Voyager is beginning to explore the final frontier of the solar system."</p>
<p>Scientists analyzing data from Voyager 1 disagree as to whether the probe has yet crossed over the critical boundary that marks the transition from our solar system into interstellar space. But even dissenters agree that if it has not crossed that boundary, called terminal shock, it is very close.</p>