Knockin’ on the Galaxy’s Door: Physics Professor Calculates Area at the Edge of the Solar System

Posted: May 30, 2006 at 1:00 am, Last Updated: November 30, -0001 at 12:00 am

Voyager 1 and 2 in space
In the next ten years, scientists expect the Voyagers to cross the heliopause – the edge of the bubble created by the sun’s supersonic wind – and become the first craft to reach interstellar space.
Image courtesy NASA/JPL-Caltech

By Tara Laskowski

Merav Opher was 7 years old when the spacecraft Voyager 1 launched in 1977.

Now, almost 30 years later, Voyager 1 has traveled farther than any manmade object and is nudging its way to the edge of the solar system. Voyager 2 is only a few years behind.

And Opher, assistant professor of physics and astronomy, is the only female scientist – and by far one of the youngest scientists – working to calculate the flow of particles and magnetic fields of the area the spacecrafts are venturing into.

Many millions of miles past Pluto, the solar wind of our sun begins to lose its dominance when it comes into contact with the interstellar wind from the rest of our galaxy.

Scientists consider the place where the two winds meet – called the heliopause – as the edge of our solar system, and Opher and her colleagues are eager to have a greater understanding about what happens in that area and beyond.

Merav Opher
Merav Opher
Creative Services photo

“We’re piercing a hole in the curtain that separates us from the rest of the galaxy. For the first time, we are looking to the outside, to what lies beyond us,” says Opher.

In December 2004, scientists announced that Voyager 1 had crossed the Termination Shock, which is the area where the million-mile-per-hour solar wind slows to about 250,000 miles per hour.

The spacecraft then entered an area called the heliosheath, where wind is slower, hotter and denser as it interacts with the surrounding interstellar matter.

“Where the interstellar wind and the solar wind meet, there is a clash, kind of like where a waterfall hits a river,” says Opher. “The two winds go through a shock, and we are very interested in the physics of this area.”

Joining the Voyager Team

Opher has been working on calculations of the area since 2001, when she was a postdoctoral student with Paulett Liewer at the Jet Propulsion Laboratory. Opher adapted a very advanced code developed by Tamas Gombosi at the University of Michigan to calculate the area the Voyager craft was approaching.

The findings were so exciting that Opher was eager to share them with Ed Stone, the principal investigator of the entire Voyager mission.

“He was just across the street, practically, working on the same thing I was interested in,” says Opher. “So one day I just called him up. I shared my results with him, blabbed on and on about the interesting things I was finding, and finally he just told me to come over and meet with him. That’s when we started working together.”

For Opher, it was an opportunity to work with one of her heroes.

“It took me awhile to get comfortable with him. I had grown up watching him and listening to him talk about all the amazing discoveries Voyager was making.”

Not only is Opher the only female scientist working on these problems, but she’s also decades younger than the principal investigators of the Voyager mission. Stone and most of the other team members are in their 70s, whereas Opher is only 36.

“I’ve learned a lot from them, and I’ve been able to teach them some, too.”

Data from a “Weird Place”

Although technology has dramatically improved since 1977, Voyager 1’s instruments are still sending back valuable data, and Opher and the rest of the Voyager team have been surprised at the data they are getting from the spacecraft as it passes through the shock.

heliosphere image
Computer simulation of the interaction of the solar wind with the interstellar wind. The termination shock (in yellow) is being pierced by the solar magnetic field lines (black). The interstellar magnetic fields are shown in white lines.
Image courtesy Merav Opher

One of the most important discoveries Opher has found is that the solar system is asymmetric. While scientists thought the northern and southern hemispheres would be similar, they have found that the southern hemisphere is more compressed. Even the eastern and western hemispheres don’t look the same.

“It’s a weird place,” admits Opher. “The physics is very different from anything we’ve ever seen.”

The team of scientists is also looking at how the magnetic fields change at the edge of the solar system. When Voyager 2 crosses the shock in a few years, the team will be able to confirm their calculations with the data they receive from that craft.

In June, Opher will present one of the Parker Lectures at the joint meeting of the Solar Physics Division and the American Geophysical Union to be held at the University of New Hampshire. This prestigious invitation allows scientists to present to a general audience an aspect of a new solar system discovery. She will present her findings about the heliosphere and what the team has learned about the edge of the solar system.

“We’ve never had an idea of what our backyard looked like, and now we have a chance,” she says. “Nature is trying to tell us something, and it’s really neat to get to listen.”

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