Searching for Stardust
If you're like the average person, chances are you'll never get to name a star. But how would you like to name a tiny, tiny piece of one?
Image to left: Stardust encountered Comet Wild 2 in January 2004. Credit: NASA
Earlier this year, NASA's Stardust mission delivered back to Earth its sample-return canister, with a much-publicized cargo of dust particles from the comet Wild 2 (pronounced Vilt 2). Stardust passed so close to the comet in January 2004, it was able to collect a pristine concentration of particles from the comet's nucleus (or coma). In addition to the comet samples, the Stardust canister contained something else: interstellar grains from the furthest most reaches of our solar system called "stardust." And we need your help finding these tiny interstellar particles.
Compared to most of space, the solar system is rather crowded, with its planets, comets, asteroids and other bodies. Between these objects, however, are vast expanses of near-nothingness, or voids. However, even these "voids" are not truly empty. Instead, they are filled with gases and dust that make up the interstellar medium, the scientific term for the "stuff" between stars. The density of the interstellar medium is very low. On average, there is about one atom of gas per cubic centimeter, and only one dust particle per cubic kilometer. In other words, if you could somehow "fill" 250 football stadiums with interstellar medium, you might find only one particle of dust.
The dust and gases that make up this interstellar medium have been ejected into space by stars, and are on a continuous voyage through space. Eventually, they make their way from one stellar system to another. That means that, between the objects in the solar system, you can find dust from other stars.
Image to right: Dust samples were collected in this aerogel grid. Credit: NASA
Some of that dust is exactly what NASA's Stardust mission collected. A stream of interstellar dust was recently discovered flowing from the direction of the constellation Ophiuchus, the serpent holder. This stream is bigger than the solar system itself. So, as the Stardust spacecraft traveled through interplanetary space, it opened its collector into the direction of the stream and captured some of the interstellar dust.
The collector captured the particles in a material called aerogel, a highly porous solid material with a very low density. When the tiny particles struck into the aerogel, they left tracks that reveal their location. However, since the particles had masses of only trillionths of a gram, the tracks they left are not very big either. Making the particles even more difficult to find is the fact that they are so unique. There are probably limited numbers captured within the collector, possibly as few as 45. With the relative size of the particles and the collector, the task will be like trying to find 45 ants in a football field.
Because the tracks are so small, scientists from the University of California at Berkeley, in collaboration with NASA, are using a robotic microscope to take pictures of the aerogel at very high magnification. To image the entire collector using that method will require taking more than 1.6 million video clips.
Image to left: Tracks have already been found in the aerogel that collected comet dust samples. Credit: NASA
That's where the really hard part of finding the particles comes in. To find all of the interstellar dust particles, someone must look at all 1.6 million of those videos. Each video will have to be studied carefully to see if it shows any dust tracks. It's going to be really hard work, and it's going to take a lot of time. That's why we need your help.
Through the Stardust@home program, NASA is asking people to help find the interstellar dust particles by becoming "citizen scientists." The video clips are being placed online, so that volunteers can view them on computers with Internet connections. We estimate that it will take 30,000 hours of work to look at all of the videos. So far, over 100,000 people have volunteered to help. That means it will only take an average of 18 minutes per person to look at every clip, if every volunteer participates. More people signing up means all the particles can be found more quickly. On average, a dust particle will be discovered every four days when the project begins in April. The project will continue through November.
Stardust@home is a collaboration between NASA and the University of California, Berkeley, along with other institutions, including The Planetary Society and the University of Washington. In addition, Amazon.com donated storage space and bandwidth through which the video clips are hosted.
So why should you help? First and foremost, the project provides the opportunity for you to be a part of an exciting research project that will reveal new secrets of space science. But there’s more! The Stardust@home Web site will list volunteers who receive the highest scores on a dust-track-identification test. Users achieving a high score will also receive special certificates. The first person to find a track will be given the privilege of naming that dust particle, and will be listed as a co-author on scientific papers about the discovery.
Image to right: Scientists believe Stardust’s aerogel grid may contain as few as 45 particles of interstellar dust. Credit: NASA
The Stardust@home project will also supply related educational materials for educators to use with students, and will provide professional development training on the materials.
Stardust@home is looking for very, very small particles, but it’s a very big opportunity for you to help space scientists learn more about our galaxy.
David Hitt/NASA Educational Technology Services