What's in our Solar System?

Since ancient times, scientists have mapped the locations of thousands of objects in the sky every night. Most appear to stay in the same place from night to night, but some change positions over time. While many ancient cultures studied these curious objects, the name that stuck came from the Greek word for “wanderer:” planete, or planet. And once telescopes became common, scientists realized that planets weren’t the only wanderers—our Solar System has millions of wandering asteroids and comets too!

But these objects are hard to find—they’re small, far away, and usually dark. While scientists have found about a million asteroids and comets so far, they believe there are tens of millions distributed among and beyond the planets. And the farther away these objects are, the fainter they are and the harder they are to find.

Rubin Observatory will take images of the entire Southern Hemisphere night sky every few nights, over and over for ten years. With so many repeated images, we’ll know what the sky usually looks like, so we’ll notice when something changes in brightness or position. Scientists will use sophisticated software to identify wandering Solar System objects and study properties like their sizes, what they're made of, and their orbital paths around the Sun. Rubin Observatory will excel at detecting faint objects, and it’ll find 10-100 times more Solar System objects than were known before. The information it gathers about these objects will help scientists classify them into different groups and learn about how the Solar System came to look the way it does.

Many of the discoveries will be of near-Earth objects, and it’s possible that some could be on a collision course with Earth. Scientists have already found most of the near-Earth objects bigger than 1 km in size, but they’ve found less than 30% larger than 140 m in size—which would still cause major devastation. Rubin discoveries will increase that percentage to 60-90%—that’s a huge improvement, since we want the earliest warning possible for any potential impacts!

Other objects we’ll find will be in the asteroid belt between Mars and Jupiter. Many of these discoveries will be small, faint asteroids, which will help scientists understand how objects (big and small) have smashed into each other and broken apart through the Solar System’s history.

A third group of objects we’ll find will be in the Kuiper Belt, a disk of asteroids and comets farther away from the sun than Neptune. This region is the best test bed we have to study the environment in which the Solar System formed, because it’s generally far away from gravity or radiation influences that could drastically change the properties of objects in it. But because objects in the Kuiper belt are so faint and far away, they’re especially hard to find. Thanks to Rubin’s ability to find such faint and distant objects, scientists will find more Kuiper Belt objects than ever before.

Using Rubin data, we’ll find even more kinds of objects than these. Some will be part of groups we’ve never seen before, and all of the discoveries will help scientists work out the story of the Solar System’s history. We can’t wait to see what they’ll find out!