NASA's Voyager I (search) spacecraft has entered the final frontier of our solar system and is cruising its way to a vast area marking the beginning of interstellar space.

The spacecraft, launched 28 years ago, is 8.7 billion miles from the sun in a region called the heliosheath (search), located just beyond the termination shock, or precursor of the boundary that marks the beginning of interstellar space.

"Voyager I has entered the final lap on its race to the edge of the interstellar space," said Edward Stone, project scientist at the California Institute of Technology (search) in Pasadena, which manages NASA's Jet Propulsion Laboratory.

The findings were presented Tuesday at the American Geophysical Union meeting in New Orleans.

Voyager I still has a decade to go before reaching the heliopause, which marks the beginning of interstellar space and the end of our solar system. Beyond, it's the interstellar medium, made up of the particles cast off by dying stars.

There was disagreement in 2003 over whether the spacecraft penetrated the termination shock, where the solar wind slows abruptly, becoming denser and hotter.

Scientists said recent evidence shows the spacecraft's instruments recorded a sudden increase in the solar wind's magnetic field, which happens when the solar wind slows down.