Dust Simulations Paint Alien's View of the Solar System (transcript)

Narrator: Astronomers have just begun imaging planets around other stars the technique isn't very advanced yet, and it can't see any planets as small as those in our own solar system. But let's suppose for a moment that alien astronomers are looking at our planetary system. Could they find any evidence that planets exist around the sun, even if they couldn't see the planets themselves?

The answer is probably yes. That's because at least one world in our solar system would make its presence known by its effects on a huge cloud of dust at the fringes of the solar system in a place called the Kuiper Belt. The Kuiper Belt is a kind of cold storage zone out beyond Neptune, occupied by millions of icy bodies, including Pluto. The icy objects in the Kuiper Belt release dust that from afar, could appear as a hazy disk at infrared wavelengths. New computer models created by NASA scientists, shown here, reveal what dust in the Kuiper Belt might look like to an alien astronomer.

Neptune creates the intricate pattern. The massive planet's gravity tugs on the clouds dust grains, nudging them in their orbits. Stark: Neptune creates a ring structure in the dust cloud which features a gap where the planet itself resides. And this gap should make it fairly easy to tell where Neptune is from afar, even at distances where the planet is too dim to detect directly.

The supercomputer simulations that Marc Kuchner and I performed also allow us to see what the dust in the solar system may have looked like when the solar system was much younger. In effect, we can go back in time and see how the distant view of the solar system may have changed. Narrator: In its youth, the Kuiper Belt contained many more objects and, consequently, lots more dust.

In fact, the dust was so thick that the particles themselves often collided. Stark: When we included collisions between dust particles, we were really amazed by what we saw.

Narrator: Successively younger models of the Kuiper dust cloud show progressively simpler structure, eventually leading to a single narrow ring beyond Neptune's orbit. Stark: Dust collisions change Neptune's gravitational imprint. The gap in the ring disappears.

The amazing thing is, we've already seen ring structures like this around other younger stars, like Fomalhaut. In terms of dust, we now know that these other systems may look similar to our young solar system. Narrator: Dust around other stars can tell us a lot about possible planets, just as in our own solar system, it could reveal Neptune.