Voyager Finds Three Surprises Near Our Solar System's Edge

September 27, 2005

A trio of surprise discoveries from NASA's Voyager 1 spacecraft reveals intriguing new information about our solar system's final frontier. The findings appear in the Sept. 23 issue of Science.

The surprises come as the hardy, long-lived spacecraft approaches the edge of our solar system, called the heliopause, where the sun's influence ends and the solar wind smashes into the thin gas between the stars.

"These are just the most recent of many surprises Voyager has revealed in its 28-year journey of discovery. They tell us that the interaction of our sun with the surrounding interstellar matter from other stars is more dynamic and complex than we had imagined, and that there is more yet to be learned as Voyager begins the final leg of its race to the edge of interstellar space," said Dr. Edward Stone, Voyager project scientist at the California Institute of Technology in Pasadena.

Voyager 1 is expected to pass beyond the heliopause into interstellar space in eight to 10 years, with Voyager 2 expected to follow about five years later.

Voyager 1 has already passed the termination shock, where the million-mile-per-hour solar wind abruptly slows and becomes denser and hotter as it presses against interstellar gas. It was expected the wind beyond the shock would slow to a few hundred thousand miles per hour. But the Voyager scientists were surprised to find that the speed was much less, and at times the wind appeared to be flowing back inward toward the sun.

"This could mean that the outward pressure of wind was decreasing as the sun entered the less active phase of its 11-year cycle of sunspot activity," said Stone.

Another surprise: the direction of the interplanetary magnetic field in the outer solar system varied more slowly beyond the termination shock. As the sun rotates every 26 days, the direction of the field alternates every 13 days.

That field is carried out by the solar wind, with the alternating directions forming a pattern of zebra stripes moving outward past the spacecraft. One could imagine a zebra with giant "magnetic stripes" running past the spacecraft and Voyager 1 "observing" an alternating stripe every 13 days. After the shock, the "zebra" with its stripe pattern was moving at nearly the same speed as Voyager, so that it took more than 100 days for the stripe to pass the spacecraft and for the magnetic field to switch directions.

Perhaps the most puzzling surprise is what Voyager 1 did not find at the shock. It had been predicted that interstellar ions would bounce back and forth across the shock, slowly gaining energy with each bounce to become high speed cosmic rays.

Because of this, scientists expected those cosmic ray ions would become most intense at the shock. However, the intensity did not reach a maximum at the shock, but has been steadily increasing as Voyager 1 has been moving farther beyond the shock. This means that the source of those cosmic rays is in a region of the outer solar system yet to be discovered.

Still operating in remote, cold and dark conditions billions of miles from the sun, the Voyager 1 and 2 spacecraft owe their longevity to radioisotope thermoelectric generators which produce electricity from the heat generated by the natural decay of plutonium.

Caltech manages NASA's Jet Propulsion Laboratory in Pasadena, which built and operates Voyager 1 2. NASA's Goddard Space Flight Center, Greenbelt, Md., built the magnetometers.

Copyright 2005 by Space Daily, Distributed United Press International

Explore further: It's showtime for Pluto; prepare to be amazed by NASA flyby

Related Stories

What will Voyager 1 discover at the bow of the solar system?

July 15, 2013

As the Voyager 1 spacecraft approaches the very edges of our solar system, space scientists await to see if it will discover the solar system's 'bow shock'; a theorized pile up of gas, dust, and cosmic rays, which accumulate ...

Voyager observes magnetic field fluctuations in heliosheath

October 29, 2012

As they near the outer reaches of the solar system, for the past several years the two Voyager spacecraft have been sending back observations that challenge scientists' views of the physics at the edge of the heliosphere, ...

No more solar wind for Voyager 1 spacecraft

December 13, 2010

( -- The 33-year odyssey of NASA's Voyager 1 spacecraft has reached a distant point at the edge of our solar system where there is no outward motion of solar wind.

The Stars My Destination

November 10, 2009

The Voyager spacecraft are now in the outermost layer of the heliosphere, traveling toward interstellar space - the first man-made spacecraft to travel such a vast distance from Earth.

Voyager 1 revealing regularity of interstellar shock waves

December 16, 2014

(—The "tsunami wave" that NASA's Voyager 1 spacecraft began experiencing earlier this year is still propagating outward, according to new results. It is the longest-lasting shock wave that researchers have seen ...

Recommended for you

Building a better liposome

October 13, 2015

Using computational modeling, researchers at Carnegie Mellon University, the Colorado School of Mines and the University of California, Davis have come up with a design for a better liposome. Their findings, while theoretical, ...

Team extends the lifetime of atoms using a mirror

October 13, 2015

Researchers at Chalmers University of Technology have succeeded in an experiment where they get an artificial atom to survive ten times longer than normal by positioning the atom in front of a mirror. The findings were recently ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.