NASA photograph of one of the two identical Voyager space probes Voyager 1 and Voyager 2.

Credit: NASA

Why Did It Take NASA A Year To Realize The Voyager Left The Solar System?

September 13, 2013

For the first time in history, we've left the solar system. 

NASA has announced that new data confirms their Voyager 1 spacecraft, launched way back in 1977, exited the solar system more than a year ago, entering interstellar space.

If you're wondering what exactly interstellar space is, Merav Opherassistant professor of astronomy at Boston University and a Voyager team scientist explained that it's an area filled with material from past dead stars and wind.

(Check out my full interview with Opher last year)

What's the big deal about entering interstellar space?

"It really is a milestone," said Opher. "It's the first man-made object to cross the last boundary that separates our home. Voyager is like our spy that we sent to tell us what lies beyond our home."

One curious thing about the announcement is that it took NASA more than a year to make it. Chief Voyager scientist Ed Stone said the team needed time to analyze those observations and make sense of them. One of the reasons the data was so hard to analyze is that the environment of interstellar space isn't quite what scientists anticipated.

"All along, scientists expected the magnetic field to change direction from east-west to north-south when the spacecraft entered interstellar space," said Opher.

But it didn't.

And so on August 27, 2012, when scientists saw a drop off in solar particles around Voyager that strongly suggested we were outside the solar system, they figured they couldn't be in interstellar space yet. 

But new data about the density of the matter around the spacecraft has proven to be the straw that broke the camel's back - undeniable evidence that we are outside the solar system. And now that scientists know they aren't waiting for the magnetic field to change direction, they've concluded that the moment the solar particles dropped off was indeed the moment Voyager broke thorough. 

Opher and some of her colleagues think we were out even earlier- on July 28, 2012 when the magnetic field didn't change direction, but sort of flipped from east-west to west-east. 

The 36-year-old Voyager 1 is now about 12 billion miles from our sun, and will continue to transmit data -- and perhaps surprise and confound scientists -- from interstellar space. 

WGBH News is supported by:
Back to top