The Kuiper Belt orbits around the sun just beyond the orbit of Neptune. It covers a vast region of space starting about 2.7 billion miles (4.4 billion kilometers) from the sun. It stretches to about 9.3 billion miles (14.9 billion kilometers) away from the sun.
Here’s another way of thinking about it. The distance from the sun to the Earth is described as 1 atomic unit (AU). The Kuiper Belt stretches from 30 AU to 100 AU from the sun. That means the distance from the inside edge of the Kuiper Belt to its outside edge is much wider than the region inside the Kuiper Belt, the region from the sun to Neptune! (Compare that to the Asteroid Belt, which is only 140 million miles wide.)
If you have ever seen a model of the solar system, you know the eight planets all travel in the same plane around the sun. Their orbits–the paths they take–look like a disc (or flat plate) of rings around the sun. The Main Asteroid Belt also orbits around the sun, between the orbits of Mars and Jupiter, along this same plane. The Main Asteroid Belt is flat.
Unlike the Main Asteroid Belt, the Kuiper Belt is not flat. It is donut-shaped with icy bodies orbiting the sun above and below the plane or disc formed by the orbits of the planets.
The largest object in the Kuiper Belt is the dwarf planet Pluto. Astronomers once called Pluto a planet, but in 2006 it was reclassified as a dwarf planet. Like other planets, it orbits the sun and it has enough mass to have formed a round shape, instead of the bumpy, irregular shape of an asteroid. But Pluto’s gravity has not cleared a path through Pluto’s orbit of asteroids and other bodies.
Most of the objects floating in the Kuiper Belt are small clumps of rock and ice. These are ancient remnants left over from the formation of our Solar System.
1) The robot explorers include a car-sized rover and a helicopter
The rover, named Perseverance, weighs 2,260 pounds. (For comparison, my 2003 Honda Civic weighs about 2,400 pounds.) Perseverance will explore the Jezero Crater, which once held a river and a lake on Mars. Today, Mars is cold and dry. Perseverance will be looking for signs of water, ice made from water, and signs of ancient, microscopic life.
Perseverance and its specialized equipment will:
Collect rocks to send back to earth so scientists can examine them in detail for signs of ancient life.
Use radar to search for ice made from water underneath the ground.
Test a machine that will generate oxygen from Mars’s carbon dioxide atmosphere.
Helicopter on Mars!
Perseverance will also launch a small, 4-pound helicopter named Ingenuity. This will be a first for NASA and all Earth’s space explorers! Never before have humans operated a rotary-winged aircraft–or rotorcraft–on an alien world.
Ingenuity will help NASA test whether rotorcraft will make good explorers of planets with an atmosphere. Helicopters may make good survey craft that can quickly map large sections of planets and find locations of interest for rovers to examine in more detail.
2) The mission will provide historic audio and video records
Perseverance has 23 cameras and two microphones. Some of those cameras will capture footage of Perseverance’s touchdown on Mars, scheduled for Feb. 18, 2021. One of the microphones will also record the landing.
The other microphone will record Perseverance as it explores the Martian surface and drills into the Martian rock.
3) Perseverance and Ingenuity were named by kids
Alex Mather, a seventh-grader from Virginia, submitted the name Perseverance. Vaneeza Rupani, a high-school junior from Alabama, recommended the name Ingenuity. Both got to watch the launch in person at Cape Canaveral in Florida.
What is the timeline for Perseverance’s mission?
A United Launch Alliance Atlas V rocket carrying Perseverance and Ingenuity launched today at 7:50 AM eastern time. Perseverance will travel through space for seven months to reach Mars. A rocket-powered crane will lower Perseverance to the Martian surface on Feb. 18, 2021. Ingenuity will be strapped to the belly of Perseverance. The two machines will explore Mars for at least one Martian year, which is almost two Earth years.
Perseverance will collect at least 20 rock samples. NASA is planning a joint mission with the European Space Agency to pick up those samples and bring them back to Earth as early as 2031.
Today is Wednesday, so it’s time for our regular feature What is that? Here’s today’s term:
Comet – an object orbiting the sun made of rock and ice that grows a “tail” of vapor and dust when it approaches the sun
Comets are sometimes described as “dirty snowballs” because they are made of a mixture of both ice and rock and dust. They orbit the sun in an elongated, oval path that can take hundreds or even millions of years to complete. They may spend much of their time traveling through the Kuiper Belt, a region of space beyond Neptune, the furthest planet from our sun.
Comets are different from asteroids, which tend to be composed of rock and/or metals, because they contain large amounts of ice–frozen water and other frozen gases.
This image of Comet Ison, published in 2013, was made from combined photos taken through blue and red filters. Source: NASA/ESA/Hubble Heritage Team (STScI/AURA).
“When frozen, they are the size of a small town. When a comet’s orbit brings it close to the Sun, it heats up and spews dust and gases into a giant glowing head larger than most planets,” according to NASA.
When a comet’s orbit brings it near to the Sun, the Sun’s warmth heats up the comet’s ice. The melted ice boils off and the comet’s ice, dust, and rock surface make a cloud around the comet. As the cloud trails behind the comet it leaves a wide path of particles millions of miles long. The sun lights up this tail, sometimes making it visible on Earth.
Parts of a comet
Nucleus–the main body of the comet, which is made of frozen gases, rock and dust
Coma–the cloud of particles and gases that form around the comet nucleus when it is heated by the Sun
Head–when a comet is traveling near the sun, and a coma forms, the head is the nucleus and coma, which may be 600,000 miles (1 million kilometers) across. The head is a bright cloud of particles and gases lit by the sun.
Tail–when the comet is near the sun and the coma forms, the tail is the long trail of particles and gases left behind the head as it hurtles through space. Tails can stretch for millions of miles.
How many comets are there in our solar system?
Scientists estimate there are billions of comets orbiting the Sun in paths that pass far outside Neptune’s orbit. They travel in the far distant portions of our solar system called the Kuiper Belt and the Oort Cloud.
Although scientists think there are billions of comets, we have only discovered and named less than 4,000 comets.
How are comets named?
A comet is usually named after the person that discovered it. Halley’s Comet, perhaps the most famous comet, is named after Edmond Halley, an English astronomer. He studied historical reports of other astronomers and suggested that reports of a comet appearing every 75 years might be the same comet. He predicted it would appear again in 1758. He was right and the comet was named after him. But he did not live long enough to see its return and his theory proven.
Halley’s comet will not appear to us on Earth again until 2061.
Many comets now have the names of spacecraft in their names–names like Linea, Soho and Wise–because spacecraft (and their operators) are very good at finding comets.
Design your own comet!
Imagine you discovered a comet flying through space and it was named after you. What would it look like? What types of ices and rock would it be made of? How long would it take to orbit the Sun? What year would we see it next in Earth’s nighttime sky?
Asteroid – lump of rock or metal that orbits the sun
An asteroid, a word also meaning “like a star,” is a lump of rock or metal–and sometimes ice–that orbits the sun. Some orbit the sun directly, some orbit other planets, and some orbit our entire solar system.
What is the Asteroid Belt and where is it located?
Millions of asteroids orbit the sun just like the Earth and the planets do. Most of the asteroids scientists have found are located in the Main Asteroid Belt, which is a band of asteroids 140 million miles wide. The Main Asteroid Belt starts just outside the orbit of Mars and is well inside the orbit of Jupiter, which is the next planet out from Mars.
See an amazing image of the Main Asteroid Belt here at Space.com. (The Main Asteroid Belt is shown in green.)
If you have ever seen a model of the solar system, you know the eight planets all travel in the same plane around the sun. Their orbits–the paths they take–look like a disc (or flat plate) of rings around the sun. The Main Asteroid Belt creates a thick ring on this same plane, like its part of the same disc or plate. The asteroids in the Main Asteroid Belt also travel in the same direction around the sun as all the planets of our solar system.
What are asteroids made of?
Most asteroids in the Asteroid Belt are made of rock. Some asteroids are made of metal–mostly iron and nickel. These metal asteroids are shiny and reflect the sun’s light. Some asteroids are made of a mix of rock and metal. And some more distant asteroids are made of ice. Some asteroids may even contain ice made from water, which could be useful to support astronauts if we colonize the Asteroid Belt.
Some asteroids are solid. Some asteroids are just “piles of rubble held together by gravity,” according to an article by Nola Taylor Redd on Space.com. “Most asteroids aren’t quite massive enough to have achieved a spherical shape and instead are irregular, often resembling a lumpy potato.”
How big are asteroids?
Asteroids range from the size of specks of dust to moonsize. The largest asteroid in the Asteroid Belt is the dwarf planet Ceres. It is almost 590 miles across (diameter). That is small compared to Earth’s moon, which has a diameter of 2,158 miles. But it’s much bigger than one of Mars’s moons, Deimos, which is only seven miles across.
Ceres comprises 25 percent of the mass in the Main Asteroid Belt.
There are a number of other asteroids that are 100 and 200 miles long.
What about other asteroids?
Beyond Neptune is an even wider ring of asteroids called the Kuiper Belt. The Kuiper Belt includes the dwarf planet Pluto, which astronomers once used to count among the nine planets in our solar system. There is even a snowman-shaped asteroid in the Kuiper Belt named Arrokoth.
The asteroid Eros has made history both in astronomy and science fiction.
Discovery of Eros
Two astronomers discovered Eros independently on the same day, August 13, 1898–Gustav Witt in Berlin, Germany and Auguste H.P. Charlois in Nice, France. It was the first near-Earth asteroid ever discovered.
NASA’s visit to Eros
Eros was also the first asteroid on which we have landed a spacecraft. Eros, named after the Greek god of love, was first orbited by a spacecraft, the NEAR spacecraft, on Valentine’s Day, February 14, 2000. After nearly a year orbiting and studying Eros, the NEAR spacecraft landed on Eros on February 12, 2001.
Astronomers have also used Eros to determine the distance between the sun and the Earth and to determine the combined mass of Earth and the Moon.
Eros also entered the annals of Science Fiction in the novel Ender’s Game, which won both the Hugo and Nebula awards.
In Ender’s Game, the hero Ender Wiggin travels to the asteroid Eros, which has been turned into I.F. Command, a military base and training center, to finish his military training.
“The tug reached Eros before they could see it. The captain showed them the visual scan, then superimposed the heat scan on the same screen. They were practically on top of it–only four thousand kilometers out–but Eros, only twenty-four kilometers long, was invisible if it didn’t shine with reflected sunlight.”
“The captain docked the ship on one of the three landing platforms that circled Eros. It could not land directly because Eros had enhanced gravity, and the tug, designed for towing cargoes, could never escape the gravity well.”
. . . .
“Ender hated Eros from the moment he shuttled down from the tug. He had been uncomfortable enough on Earth, where floors were flat; Eros was hopeless. It was a roughly spindle-shaped rock only six and a half kilometers thick at its narrowest point. Since the surface of the planetoid was entirely devoted to absorbing sunlight and converting it to energy, everyone lived in the smooth-walled rooms linked by tunnels that laced the interior of the asteroid. The closed-in space was no problem for Ender–what bothered him was that all the tunnel floors noticeably sloped downward. From the start, Ender was plagued by vertigo as he walked through the tunnels, especially the ones that girdled Eros’s narrow circumference. It did not help that gravity was only half of Earth-normal–the illusion of being on the verge of falling was almost complete.
[E]veryone lived in the smooth-walled rooms linked by tunnels that laced the interior of the asteroid.
“There was also something disturbing about the proportions of the rooms–the ceilings were too low for the width, the tunnels too narrow. It was not a comfortable place.”
By the end of Ender’s Game, we learn the secret of the unusual construction of the base inside Eros. But I won’t spoil author Orson Scott Card’s surprise. So read Ender’s Game and find out for yourself.
Design your own asteroid!
As we’ve seen, asteroids can be any shape you want. What shape would you make your asteroid? Would you create a military base or a shopping mall inside it? Or would you make a theme park or a factory on the outside?
Would you add your own gravity–like I.F. Command did in Ender’s Game? Or would you let visitors enjoy the fun of zero-grav?