9 Things: What’s That Space Rock?
It’s not easy to make your way through the solar system. Small bodies of rock, metal, and ice, such as asteroids, comets, and Kuiper Belt Objects, are in constant motion as they orbit the Sun. But what exactly differentiates them from one another? For what reason, precisely, do these tiny planets capture the imaginations of astronauts? They may hold the answers to a better understanding of our common ancestry, which is a resounding answer.
Space rocks called asteroids circle the Sun without an atmosphere. They were leftovers from when our solar system was formed, and they can be anywhere from the size of a car to the size of a major metropolis. Some asteroids have a metallic composition, while others are so rich in carbon that they appear black, like coal. Rubble heaps, only held together by their weight, are one type, while solid rocks are another.
The vast majority of the solar system’s asteroids are concentrated in the central asteroid belt. Hundreds of thousands, if not millions, of asteroids, are contained between Mars and Jupiter in this enormous doughnut-shaped ring. Contrary to popular belief, however, there is much room between each asteroid. With all due respect to C3PO, the chances of avoiding an accident while passing through the asteroid belt are pretty favorable.
Asteroids (and comets) can also enter Earth’s neighborhood if their orbits take unusual paths. They are referred to as NEOs or near-Earth objects. We can keep tabs on the ones we have found and foretell their future movements. For this purpose, there is the Minor Planet Center (MPC) and the Center for Near Earth Object Studies (CNEOS) at the Jet Propulsion Laboratory. As new asteroids and comets are discovered with ground-based and space-based telescopes, the MPC and CNEOS, in collaboration with their international peers, establish their orbital paths and assess whether or not they represent an impact risk to Earth.
Thanks to their preservation in space’s vacuum for billions of years, asteroids serve as time capsules for an early solar system for scientists. Furthermore, the central asteroid belt may have provided the inner planets, such as Earth, with water and organic molecules necessary for life.
Comets resemble snowballs more than space rocks and also orbit the Sun. Every comet’s core is a nucleus made up of frozen gas pieces, rock fragments, and dust. When a comet’s orbit brings it close to the Sun, the comet heats up, ejects dust and gases, and forms a gigantic luminous ball called a coma around its nucleus, as well as two tails, one consisting of dust and the other created of excited gas (ions). The tails, which are propelled by the solar wind, point away from the Sun and can sometimes extend for millions of kilometers.
Comets and asteroids are both remnants of the early solar system’s origin roughly 4.6 billion years ago, and as such, they hold insights about the Sun and its ancestors. There are probably billions of comets in the solar system, but only 3,535 have been confirmed. Comet impacts are a possible source of Earth’s water and other chemical elements.
Space rocks and dust called meteoroids form when larger celestial bodies like planets, moons, and asteroids collide. As meteors and meteor showers, they are among the most minor “space rocks” visible to us on Earth.
A meteor is an asteroid that enters Earth’s atmosphere and travels through it at a high rate of speed. As they accelerate through the air, they generate so much heat and pressure that they glow and leave a bright trail behind them. Before reaching the Earth, most of them explode into flames. Meteors, often known as “shooting stars,” can be composed mainly of rock, metal, or a combination of the two.
The daily average of meteoritic debris falling to Earth is estimated by scientists to be roughly 48.5 tons (44,000 kg).
Showers of Meteors
At any given hour, you might expect to see a few meteors. Meteor showers occur when the number of meteors suddenly increases. They appear as the Earth travels through the debris left behind by comets. As the particles collide with Earth’s atmosphere and burn away, they leave behind a trail of light that can number hundreds or thousands. Since Earth’s orbit consistently carries it through the same regions of comet debris, we can arrange when to watch meteor showers and witness a plethora of batteries each year.
Pieces of asteroids, comets, moons, and planets that make it through the Earth’s scorching atmosphere and crash into the Earth are called meteorites. Some meteorites are more significant than a building, yet the vast majority are the size of a pebble or a fist.
Many huge meteorite impacts occurred on early Earth, causing widespread devastation. Very few well-documented cases of damage or death caused by meteorites exist in the modern era. In November 1954, Ann Hodges of Sylacauga, Alabama, was the first person in the United States to be harmed by an extraterrestrial object when an 8-pound (3.6-kilogram) stony meteorite fell through her roof.
Dwarf planets are fascinating worlds, just like their larger brothers, despite their small size. Astronomers classify things as dwarf planets if they are large enough to be formed into a sphere or ellipse by gravity but weak sufficient that other worlds impede their orbit around the Sun. Pluto is the most well-known member of the dwarf planet class, concentrated in the Kuiper Belt past Neptune. While Vesta is a giant asteroid, Ceres is the largest object in the asteroid belt. Ceres, like Pluto, have ice volcanoes and other indicators of active geology.
Disc-shaped, the Kuiper Belt is located beyond Neptune and spans roughly 30–55 astronomical units or 30–55 times the distance from Earth to the Sun. There could be a trillion or more comets and hundreds of thousands of frozen bodies in this far-flung part of our solar system.
Makemake, Haumea, and Eris are three more minor Kuiper Belt planets shrouded in mystery with Pluto. Kuiper Belt objects, like asteroids and comets, serve as time capsules, though they may be even more pristine in the frigid environment of the Kuiper Belt.
Around 186 billion miles (300 billion kilometers) from the Sun is where the cold Oort Cloud begins to form. The Oort Cloud is thought to be a massive spherical shell that encloses the Sun, planets, and Kuiper Belt Objects, while the planets of our solar system circle in a flat plane. It’s very much like a thick bubble enclosing the Solar System. Icy bodies in the Oort Cloud can be as big as mountains and even more significant in some cases.
This vast, chilly region is the most significant and farthest in the solar system. It reaches a distance of 100,000 AU (100,000 times the distance between Earth and the Sun), covering a sizable chunk of interstellar space. Oort Cloud comets can have orbital periods of thousands or even millions of years.
It’s important to remember that NASA’s Voyager 1 probe, traveling at a million miles per day, won’t reach the Oort Cloud for another 300 years. After then, the spacecraft will take over 30,000 years to travel through the Oort Cloud and out of our solar system.