The Solar System’s Edge: Oort Cloud Quiz

Surrounding the entire solar system is the correct answer. Unlike the planets or the Kuiper Belt, which sit in a relatively flat disk, the Oort Cloud is a giant, spherical shell of icy debris that wraps around the Sun and all the planets in every direction, marking the very edge of our solar system.

True. While the Kuiper Belt ends at about 50 AU (Astronomical Units) from the Sun, the inner edge of the Oort Cloud is estimated to begin between 2,000 and 5,000 AU away. It represents a vast "final frontier" that extends thousands of times further into space than the known planets.

Spherical is the correct answer. Because the Oort Cloud is so far from the Sun, the gravitational pull of passing stars and the Milky Way galaxy itself have "puffed" it out into a ball shape. This is why comets from this region can dive into the inner solar system from any direction in the sky.

Outermost region and begins thousands of AU away are the correct answers. The Oort Cloud defines the boundary of the Sun's gravitational influence. It is so distant that it takes sunlight nearly a year to reach its outer edge, whereas it takes only eight minutes to reach Earth.

Icy volatiles like water and methane is the correct answer. Because the Oort Cloud is in the "deep freeze" of interstellar space, it is filled with billions of icy bodies. These objects are remnants from the formation of the solar system, preserved for billions of years far away from the Sun's heat.

False. The Oort Cloud is so far away and its objects are so small and dark that no telescope has ever directly imaged an object while it was still inside the cloud. We only know the Oort Cloud exists because we see the icy objects (comets) when they fall toward the Sun.

Gravitational is the correct answer. The outer edge of the Oort Cloud represents the point where the Sun's gravity is finally equaled by the gravity of other nearby stars. Anything further out would likely drift away or begin to orbit a different star in the Milky Way galaxy.

Its distance means orbits take thousands or millions of years is the correct answer. Because the Oort Cloud is so far away, a comet nudged toward the Sun has a massive distance to travel. These "long-period" comets, like Comet Hale-Bopp, take so long to complete one orbit that they may only visit the inner solar system once in human history.

Gravity from passing stars and the Milky Way are the correct answers. Because the Sun’s grip is so weak at these distances, the tiny gravitational "tug" of a star passing nearby in the galaxy can knock an icy object out of its orbit, sending it diving toward the Sun.

100,000 AU is the correct answer. This distance is almost halfway to Proxima Centauri, the nearest star to our Sun. This incredible scale means the Oort Cloud is essentially a bridge between our solar system and the rest of the interstellar space in our galaxy.

True. Jan Oort noticed that certain comets came from every direction in the sky and had never been seen before. He correctly calculated that there must be a giant, spherical reservoir of these icy bodies at the very edge of the solar system that was "feeding" comets into the inner system.

Frontier is the correct answer. It is the last major structure that belongs to our Sun. Beyond the Oort Cloud lies interstellar space, the vast "empty" region between the stars. Studying the cloud helps scientists understand the true size and scale of our Sun's domain in the universe.

There are many more in the Oort Cloud is the correct answer. While the Asteroid Belt has millions of rocks, the Oort Cloud is estimated to contain trillions of icy bodies. Because the Oort Cloud is so much larger in volume, these trillions of objects are still very spread out, with huge distances between them.

It is spherical and exists in the coldest part of the solar system are the correct answers. Because it is so far from the Sun’s heat and light, it is a "deep-freeze" environment. Unlike the orbits of the eight planets, which are flat like a plate, the Oort Cloud is shaped like a giant hollow ball.

A very bright star is the correct answer. At a distance of 50,000 AU, the Sun would be much too far away to show a round disk to the naked eye. It would simply look like the brightest star in a sky filled with other stars, and it would provide almost no warmth to the frozen surface of the object.

False. Although Voyager 1 is the furthest human-made object and has entered interstellar space, it is still centuries away from the Oort Cloud. It will take Voyager 1 about 300 years to reach the inner edge of the Oort Cloud and nearly 30,000 years to pass through to the other side.

Outer is the correct answer. The inner Oort Cloud (also called the Hills Cloud) is shaped more like a thick disk, while the outer Oort Cloud is the vast, spherical shell that defines the true edge of the Sun's gravitational reach. Together, they hold the reservoir of comets that visit our sky.

To understand the history of the early solar system is the correct answer. The objects in the Oort Cloud are "pristine," meaning they haven't been changed by heat or collisions for 4.5 billion years. By studying the comets that come from the Oort Cloud, scientists can learn what the original materials of our solar system were made of.

The shape and the distance are the correct answers. The Kuiper Belt is the "immediate" outer solar system just past Neptune, while the Oort Cloud is the "deep" outer solar system. Both are made of icy materials, not gas, and both are located extremely far away from the Earth's orbit.

True. Early in the solar system's history, the gravity of the giant planets acted like a cosmic "broom," kicking billions of icy objects out into deep space. Those that weren't thrown out completely ended up in the distant, stable orbits that we now call the Oort Cloud.