When the Voyager I space craft was launched more than 26 years ago, it carried an instrument designed to analyze the charged particles it encountered in space. That included particles around the outer planets Jupiter, Saturn, Uranus, and Pluto as well as those in the interplanetary medium.
That device—known as a Low Energy Charged Particle (LECP) detection instrument—has performed so well to date that its findings now may have made science history. According to one of the instrument’s designer, NJIT Distinguished Research Professor and physicist Louis J. Lanzerotti, the data it transmitted show that for 200 days starting about August 1, 2002, Voyager I left our sun’s sphere of influence in our galaxy. In doing so, Lanzerotti and colleagues say in an article to be published Nov. 6, 2003 in the journal Nature, Voyager I thus exited the heliosphere—the interplanetary medium, a region comprised mainly of particles emitted by the sun—encountered the “termination shock.” That is the term scientists use for the boundary between the heliosphere of our sun and the unknown regions beyond.
Scientists have theorized that as the solar wind emitted by our sun pushes out into space, at some point it will meet up with opposing streams of particles emitted by the other stars in space, that is, the interstellar medium. They have debated how far away from the sun the heliosphere extends. That endpoint would also mark the outside edge of our solar system. Scientists have dubbed this edge the termination shock—a place where the more familiar solar wind starts being buffeted by whatever wind is coming from other stars in the galaxy.
One of Voyager I’s missions is to gather data on the nature of these particles and their magnetic fields. In addition to adding to a growing body of scientific knowledge on the nature of the deepest regions of the solar system, the findings may also have applications on our own solar weather at Earth, and with it, implications for power systems and communications systems.
Lanzerotti, who is also a consultant at Lucent’s Bell Laboratories in Murray Hill, NJ, says that Voyager I data show that the termination shock zone is at a distance 85 times that of the earth from the sun, or 85 astronomical units (AU.)
The Nature article “Evidence that Voyager I Exited the Solar Wind at ~85 AU,” whose lead author is Johns Hopkins University Applied Physics Laboratory physicist Stamatios “Tom” Krimigis, is in the form of a debate. Another team of scientists argues that the data is inconclusive.
But a scientist assigned by Nature to comment on the debate agrees in the Nov. 6 issue with the Lanzerotti team.
According to Lanzerotti, the spacecraft remained outside the heliosphere for over six months, until solar eruptions caused the solar wind to pick up speed. That generated enough force to pull the Voyager I craft back inside the heliosphere, the team says.
The findings are due to be presented November 5, 2003 at a National Aeronautic and Space Administration (NASA) news conference.
Voyager I was launched from the Kennedy Space Center at Cape Canaveral, Florida on September 5, 1977. The launch vehicle was a Titan III E Centaur rocket. The spacefraft weight at launch was 1,797 pounds. It is about the size of a subcompact car. [More on VOYAGER]
The LECP instrument, which Lanzerotti was involved in designing and calibrating is designed to detect low-energy particles around the outer planet magnetospheres, as well as in the interplanetary medium. In addition to the charged particle detector telescopes, it has a rotating stepper platform on which the detectors are mounted, in-flight calibration sources, and a sunshield. [NASA LECP graphic].
Lanzerotti says the long wait to see how well the LECP would perform has gone faster than he expected. “It wasn’t really quite that bad, waiting 26 years. We passed the time by analyzing all the fantastic data we got from Voyager in 1979, 1986, and 1992,” as it encountered planets. The next big event will occur in about two years as Voyager II nears the Terminal Shock. “That will be the real test of our hypothesis,” he says.
Lanzerotti says that in designing the LECP instrument, one of the greatest hurdles in was convincing NASA that very thin semiconductors—never used back in 1977—would perform. “NASA didn’t think they would work, but they did,” he says, “they are quite common now.”
The team consists of the following members:
- S.M. Krimigis, R.B.Decker E.C. Roelof; Applied Physics Laboratory, The Johns Hopkins University
- G. Gloecker, D.C. Hamilton, Department of Physics, University of Maryland
- L.J. Lanzerotti, NJIT, Newark NJ and Bell Laboratories, Murray Hill, NJ
However, Dr. Louis J. Lanzerotti is available for pre-release interviews, meaning you can talk to him but the story has to hold until the embargo date. To arrange an interview call Gale Scott at the NJIT university communications office (973) 596-3438. Dr. Lanzerotti can be reached directly today Nov. 4, at NJIT at (973) 596-5343 On Wednesday, Nov. 5, he can be reached at (908) 582-2279
EDITORS NOTE: This Release is embargoed for release at 1 p.m. Wednesday, Nov. 5, 2003.