Excerpt
Introduction
The Sun may seem like the most important part of the solar system, but there’s a lot more out there than just planets orbiting a giant ball of fire. Past Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, past the asteroids, past the biggest planets and their swirling moons, something strange and icy stretches far beyond what most people think of as the solar system. It’s the Kuiper Belt, and it’s Pluto’s home.
This part of space is cold, dark, and packed with frozen leftovers from the early days of the solar system. It’s full of objects that never quite became planets—icy worlds, dwarf planets, and tiny, frozen rocks drifting in the deep freeze of space. If the solar system were a giant backyard, the Kuiper Belt would be the fence at the very edge, separating what we know from the mysteries beyond.
Pluto is the most famous member of this faraway region, but it’s far from alone. There are thousands, maybe millions, of frozen objects in the Kuiper Belt, ranging from tiny specks of ice to dwarf planets as big as—or even bigger than—Pluto. Astronomers are still discovering new ones. Some of these distant worlds even have moons of their own, spinning silently in the cold emptiness of space.
At this distance from the Sun, everything moves at a slow, steady pace. Unlike the inner planets, which whip around the Sun quickly, Pluto and its neighbors take a long time to complete a single orbit. Pluto, for example, takes 248 Earth years to go around the Sun just once. That means if you were born on Pluto, you wouldn’t even be one year old yet!
Out here, sunlight is weak. The Sun, which looks blazing bright from Earth, appears more like a tiny, faraway star. The temperatures are unimaginably cold—hundreds of degrees below freezing. This is a place where ice isn’t just made of water. There’s frozen nitrogen, methane, and even carbon monoxide. Substances that are gases on Earth become solid ice in the Kuiper Belt, creating landscapes that would look completely alien to us.
Even though the Kuiper Belt is incredibly far away, scientists have figured out ways to study it. Telescopes on Earth help us spot distant icy objects, but we’ve also sent a spacecraft right into the Kuiper Belt to get a closer look. In 2015, NASA’s New Horizons spacecraft reached Pluto after nearly a decade of traveling through space. It sent back stunning images, revealing mountains made of ice, giant frozen plains, and even a thin, hazy atmosphere around Pluto.
But Pluto wasn’t the only stop on New Horizons’ journey. After flying past Pluto, the spacecraft kept going deeper into the Kuiper Belt and found another object called Arrokoth. This small, oddly shaped world looks like two snowballs stuck together. Scientists think it’s one of the best-preserved pieces of the early solar system, meaning it hasn’t changed much since the time planets were first forming.
The Kuiper Belt may seem like a quiet, frozen place, but it holds clues about how the entire solar system was formed. Long ago, before Earth, Mars, or even Jupiter took shape, the Sun was surrounded by a swirling cloud of dust, gas, and ice. Some of that material clumped together to form planets. Other pieces got pushed outward by the gravity of massive planets like Jupiter and Neptune. Those icy leftovers ended up at the edge of the solar system, becoming the Kuiper Belt.
Scientists believe some of these icy objects don’t always stay in the Kuiper Belt. Every once in a while, the gravity of Neptune or another planet can send one of these frozen travelers inward, into the solar system. These visitors become comets, the bright, glowing objects with long tails that sometimes streak across our sky. Many of the comets seen from Earth come from the Kuiper Belt, carrying bits of the early solar system with them.
The Sun may seem like the most important part of the solar system, but there’s a lot more out there than just planets orbiting a giant ball of fire. Past Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, past the asteroids, past the biggest planets and their swirling moons, something strange and icy stretches far beyond what most people think of as the solar system. It’s the Kuiper Belt, and it’s Pluto’s home.
This part of space is cold, dark, and packed with frozen leftovers from the early days of the solar system. It’s full of objects that never quite became planets—icy worlds, dwarf planets, and tiny, frozen rocks drifting in the deep freeze of space. If the solar system were a giant backyard, the Kuiper Belt would be the fence at the very edge, separating what we know from the mysteries beyond.
Pluto is the most famous member of this faraway region, but it’s far from alone. There are thousands, maybe millions, of frozen objects in the Kuiper Belt, ranging from tiny specks of ice to dwarf planets as big as—or even bigger than—Pluto. Astronomers are still discovering new ones. Some of these distant worlds even have moons of their own, spinning silently in the cold emptiness of space.
At this distance from the Sun, everything moves at a slow, steady pace. Unlike the inner planets, which whip around the Sun quickly, Pluto and its neighbors take a long time to complete a single orbit. Pluto, for example, takes 248 Earth years to go around the Sun just once. That means if you were born on Pluto, you wouldn’t even be one year old yet!
Out here, sunlight is weak. The Sun, which looks blazing bright from Earth, appears more like a tiny, faraway star. The temperatures are unimaginably cold—hundreds of degrees below freezing. This is a place where ice isn’t just made of water. There’s frozen nitrogen, methane, and even carbon monoxide. Substances that are gases on Earth become solid ice in the Kuiper Belt, creating landscapes that would look completely alien to us.
Even though the Kuiper Belt is incredibly far away, scientists have figured out ways to study it. Telescopes on Earth help us spot distant icy objects, but we’ve also sent a spacecraft right into the Kuiper Belt to get a closer look. In 2015, NASA’s New Horizons spacecraft reached Pluto after nearly a decade of traveling through space. It sent back stunning images, revealing mountains made of ice, giant frozen plains, and even a thin, hazy atmosphere around Pluto.
But Pluto wasn’t the only stop on New Horizons’ journey. After flying past Pluto, the spacecraft kept going deeper into the Kuiper Belt and found another object called Arrokoth. This small, oddly shaped world looks like two snowballs stuck together. Scientists think it’s one of the best-preserved pieces of the early solar system, meaning it hasn’t changed much since the time planets were first forming.
The Kuiper Belt may seem like a quiet, frozen place, but it holds clues about how the entire solar system was formed. Long ago, before Earth, Mars, or even Jupiter took shape, the Sun was surrounded by a swirling cloud of dust, gas, and ice. Some of that material clumped together to form planets. Other pieces got pushed outward by the gravity of massive planets like Jupiter and Neptune. Those icy leftovers ended up at the edge of the solar system, becoming the Kuiper Belt.
Scientists believe some of these icy objects don’t always stay in the Kuiper Belt. Every once in a while, the gravity of Neptune or another planet can send one of these frozen travelers inward, into the solar system. These visitors become comets, the bright, glowing objects with long tails that sometimes streak across our sky. Many of the comets seen from Earth come from the Kuiper Belt, carrying bits of the early solar system with them.