Projects: Stardust@home
Stardust@home FAQs
Q. What is Stardust@home?
A. Stardust@home is a space science project in which volunteers from the general public help scientists locate particles from distant stars. The particles were captured by the spacecraft Stardust and are embedded in collector plates made of aerogel, which were carried by the spacecraft. The aerogel plates, and the particles within them, were returned to Earth in a sample return capsule on January 15, 2006. The purpose of Stardust@home is to find the particles within the aerogel plates. The project is expected to launch in May 2006.
Q. What is Stardust@home looking for?
Stardust@home is looking for interstellar dust grains -- particles from distant stars that are now free-floating in space. They are extremely small, the largest being only a few microns in diameter, and are therefore very difficult to detect. In the past decade, spacecraft traveling beyond the orbit of Mars discovered that a steady stream of such particles is continually moving through our solar system as the solar system itself travels through the Milky Way galaxy.
Q. How many interstellar dust particles did Stardust bring to Earth?
A. Very few, with estimates ranging from around 40 to 100 altogether. We won't really know until we find them all. For comparison, scientists estimate that Stardust captured over a million particles from comet Wild 2.
Q. How does Stardust@home work?
A. Using an automatic optical microscope, Stardust@home scientists are creating a digital "movie" of every tiny section of the aerogel containing the interstellar dust particles. Altogether, 1.6 million movies will be needed to cover the entire 1,000 square centimeter surface of the aerogel collector! The movies will be stored in a database at the Space Science Laboratory at the University of California, Berkeley, and will be sent out electronically to Stardust@home participants around the world.
Using a "virtual microscope," each participant will scan one movie at a time to determine whether it shows the impact of an interstellar dust particle. The results will then be sent back to Stardust@home headquarters in Berkeley and a new movie will be made available for scanning by the participant.
Each movie will be sent to at least four different users, who will scan and evaluate it independently. If a majority of scanners suspect the movie shows an embedded particle, the movie will be scrutinized further by trained scientists, and the location in the aerogel collector will be examined.
Q. What is an aerogel "movie"?
A. An aerogel "movie" is a series of 40 images taken of the same minute location of the aerogel collector, with each image focused on a different depth within the aerogel. The focal points range from 20 microns above the aerogel's surface to 100 microns deep within the surface. The "movie" effect is created by moving continuously between the focus levels, which is akin to moving into and out of the aerogel.
The aerogel sample collector on Stardust
Credit: NASA / JPL
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Q. What is the "Virtual Microscope"?
A. The virtual microscope is a web-based piece of software that enables Stardust@home participants to scan the aerogel movies and search for interstellar dust particles. With the aid of the virtual microscope, one can move continuously and smoothly between the different focus levels, in effect moving into and out of the aerogel.
Q. Why are interstellar dust particles hard to locate?
A. Interstellar dust particles are tiny, the largest measuring only a few microns in diameter. Because of this they penetrate only a short way beyond the surface of the collector tiles, where the aerogel is creased and cracked after 7 years in space. So, the interstellar dust grains are few, tiny, and hidden among a host of aerogel cracks and flaws. Finding them will not be easy.
Q. Will the Virtual Microscope work on a Mac or a Linux operating system?
A. Yes. The virtual microscope is a web-based program, which means you don’t need to download it onto your computer, but only to go to the Microscope web page. All you need in order to use the Virtual Microscope is a web browser. The platform – Mac, Linux, or Windows – does not matter.
Q. What do I need to do to qualify for participation Stardust@home?
A. Before you download your first movie, you will complete a short training session that will teach you to identify interstellar dust particle tracks. You will then undergo a short test to make sure that you can indeed recognize particle tracks. The whole process should take about 20 minutes, after which you can begin processing real movies of Stardust's aerogel collector.
Q. How will I recognize a real interstellar dust particle track if I see one?
A. Impacting interstellar dust particles will leave carrot-shaped tunnels boring into the aerogel, at the tip of which will be the particle itself. When viewed with the virtual microscope, this pattern is recognizable by the fact that the round section of the tunnel can be seen continuously from the surface of the aerogel down to a considerable depth. In contrast, cracks and flaws in the aerogel will be visible at certain depths and then disappear as the virtual microscopes' focus turns to other layers.
Q. How do I sign up for the project?
A. Keep checking on the Planetary Society website (http://planetary.org) to see when the project launches. When this happens, go to the Stardust@home website at http://stardustathome.ssl.berkeley.edu/ and click on the "Test and Register" link, under "Getting Started" on the lefthand side. You will undergo a short training course and then a brief test to make sure you have acquired the basic skills of an interstellar dust particle hunter. You will be asked for your e-mail address, and then you will be ready to begin scanning Stardust movies for interstellar dust!
Q. How will I know if I found a particle?
A. You will not know for sure right away, even if you are convinced that you have found one. The particle will have to be confirmed by scientists examining the aerogel directly. However, you will be able to track your progress and discoveries on a special web page that only you can access. This page will be updated automatically, and will give you information about the number of movies you have processed and whether any possible tracks you flagged proved to be the location of a real particle.
Q. Why can't a computer program find the particles?
A. Before a "pattern recognition" computer program can identify the telltale signs of the impact of an interstellar dust particle in aerogel, it has to "learn" the pattern from existing examples of such impacts. Since interstellar dust has never before been captured in aerogel, no such examples exist! As a result, no computer program is able to recognize the pattern. In contrast, the human eye can recognize such impacts with just a minimal amount of training.
Q. How were the interstellar dust particles captured?
A. The spacecraft Stardust was equipped with a tennis-racquet shaped particle collector made of aerogel plates. In two different periods during Stardust's 7-year journey in space -- between February and May of 2000 and August and December of 2002 -- the spacecraft passed through the interstellar-dust particle stream that flows through our solar system. During those periods, Stardust extended its particle collector so that the aerogel was exposed to the particle stream. The interstellar dust grains struck the aerogel at high speeds of up to 26 kilometers per second (16 miles per second) and embedded themselves within this ultralight material. The particles will remain stored within the aerogel until they are extracted by scientists for study.
Q. What is aerogel?
A. Aerogel is a silicon-based solid, similar to glass but 1,000 times less dense. It is so porous that it is 99.8% empty space. It is transparent with a bluish tinge, and it is extremely light. Because of its ethereal appearance, it has sometimes been called "solid smoke."
Q. Why was aerogel used on Stardust?
A. Aerogel is endowed with remarkable qualities, including being 39 times more insulating than the best fiberglass insulators. For Stardust, aerogel's most important characteristic is its ability to slow down and preserve particles traveling at high speed. The cometary and interstellar dust particles encountered by Stardust were traveling ten times at speeds of around 20 kilometers (12 miles) per second relative to the spacecraft. Normally, they would be pulverized or even evaporate when encountering a solid object in their way. But aerogel is able to slow the particles down to a halt within the space of a few dozen microns, and preserve them better than any known substance.
Stardust chases comet Wild 2
An artist's depiction of Stardust closing on on comet Wild 2.
Credit: NASA, JPL
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Q. What was the Stardust mission?
A. Stardust is a sample return mission launched on February 7, 1999 to collect particles from the tail of a comet and particles of interstellar dust. For this purpose, it carried with it a tennis-racquet shaped particle collector composed of 130 aerogel cells. Between February and May of 2000, and again between August and December of 2002, Stardust passed through a stream of interstellar dust particles flowing into our solar system as it moves through the Milky Way galaxy. During these times, Stardust extended the collector and captured and preserved interstellar dust particles within the aerogel. On January 2, 2004, Stardust passed within 240 kilometers (149 miles) of the core of comet Wild 2, undergoing the heaviest bombardment ever endured by a spacecraft from the gas and debris shooting out from the comet. During this encounter, Stardust again extended the aerogel collector, capturing pristine cometary particles on the opposite side of the collector from where the interstellar dust was preserved.
Q. How did the samples return to Earth?
A. On January 15, 2006, after a voyage of 7 years and 3 billion kilometers (almost 2 billion miles), Stardust passed by the Earth and released a sample return capsule containing the cometary and interstellar dust particles it collected on its way. The capsule landed safely in the Utah desert and was transferred to the Johnson Space Center, where scientists are working to extract the particles and send them to scientists around the world.
Q. Why are scientists interested in interstellar dust?
A. Interstellar dust particles are the only matter from other stars that reaches our solar system, and scientists are eager to get their hands on them. In particular, scientists want to compare the composition and the proportions of the different isotopes that make up interstellar dust grains to those prevalent in our Sun and solar system. Are there many more "Suns" out there, or is our home star unique? Studying the composition of distant stars will help us answer that question, and Stardust's samples give scientists an opportunity to do just that.
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