Small rocks fly in space.
They go around the Sun. Some are very far away. They are not big planets. We find many of them. Can you find one in the sky?
Many small rocks fly through space.
They go around the Sun. These objects are not big planets. They are called minor planets.
Some of these rocks are called asteroids. Most stay in a ring between Mars and Jupiter. Others stay very far away. They live in cold, dark spots.
We find many new ones every month. Some have special names. Others only have numbers. Only a few have names from stories.
Scientists find them using telescopes. First, they give the rock a code. Then, they give it a number. Finally, they might pick a name.
It is fun to think about these space rocks.
They are waiting to be found!
Many small objects fly around the Sun. They are not big planets. They are also not comets. We call these objects minor planets.
Most minor planets are asteroids. Many stay in the asteroid belt. This is a ring between Mars and Jupiter. Other minor planets live far away. They stay in the Kuiper belt or the scattered disc. Some stay near the big planets. We call these trojans. They share an orbit with a planet.
Finding these rocks is a big job. Scientists find thousands every month. A new rock gets a code first. This is a provisional designation. Next, we learn its path. Then, it gets an official number. The last step is a name.
Only a few have names. Most just have numbers. Some names come from Greek stories. Others come from books or movies. Some people even name them after pets! One cat was named Mr. Spock. You cannot name a minor planet after the person who found it. This is a special rule for these space rocks.
A minor planet is a special object that orbits the Sun. It is not a full planet, and it is not a comet.
The eight official planets are much larger than these objects. One big difference is that planets clear their own paths in space. Minor planets do not clear their orbital neighborhood. This means they share their space with many other objects. Scientists often call them small Solar System bodies. This is the term the International Astronomical Union prefers to use today.
These objects live in many different places. Most asteroids stay in the inner Solar System. A famous group lives in the asteroid belt between Mars and Jupiter. Some asteroids are near-Earth objects that come close to our world. There are even Earth trojans, which share an orbit with our planet. Two of these are known as 2010 TK7 and 2020 XL5. Other minor planets live far away in the Kuiper belt. These distant objects stay past the orbit of Neptune.
Learning about these rocks has taken a long time. The first minor planet found was Ceres in 1801. At that time, people actually called it a planet. Soon after, they started calling it an asteroid instead. The specific term "minor planet" did not appear until 1841. For a long time, it was just seen as a small type of planet. In 2006, the rules changed again. The International Astronomical Union reclassified many objects into new groups. This helped scientists organize the many things they found in space.
There are hundreds of thousands of these objects to keep track of. The Minor Planet Center has documented over 213 million observations. They have found 794,832 minor planets in total. Out of these, 541,128 have orbits known well enough to get a permanent number. Only 21,922 of them have official names. Most objects are just given a number or a code. As we find more, the numbers are getting very large. They have now reached six-figure numbers.
Naming a new discovery happens in three steps. First, it gets a provisional designation, which is a temporary code. Next, once the orbit is certain, it gets an official number. Finally, the discoverer might give it a real name.
Most people use names from Greek or Roman stories. Some people even use names from movies or books. You might find an asteroid named after a pet, like 2309 Mr. Spock. However, there is a strict rule for these rocks. You cannot name a minor planet after the person who found it.
A minor planet is an astronomical object that orbits the Sun directly. According to the International Astronomical Union (IAU), these objects are classified as neither planets nor comets. While the eight major planets are massive, minor planets lack the gravity to clear their orbital neighborhood. This means they share their paths through space with many other objects. Today, the IAU prefers the term "small Solar System bodies" (SSSBs) to describe these objects. This category includes both comets and minor planets.
Minor planets are categorized by where they live and how they move. Asteroids are typically found in the inner Solar System. Many reside in the asteroid belt between Mars and Jupiter. Some are near-Earth objects, which have orbits that bring them close to our world. These include Aten, Apollo, and Amor asteroids, which are defined by their specific distances from the Sun. Some asteroids, called trojans, are gravitationally locked to the orbits of larger planets. We have found Earth trojans like 2010 TK7 and 2020 XL5, as well as Mars and Jupiter trojans.
Distant minor planets exist in the outer Solar System. Centaurs live between Jupiter and Neptune, but they have unstable orbits. Trans-Neptunian objects exist at or beyond the orbit of Neptune. Many of these are in the Kuiper belt, a region located about 55 AU from the Sun. Some are called Plutinos because they exist in a 2:3 resonance with Neptune. Other objects, called scattered disc objects, were likely pushed outward by Neptune's gravity. There are also detached objects like Sedna that stay far outside the Kuiper belt.
The history of how we name these objects has changed many times. The first minor planet discovered was Ceres in 1801. At the time, scientists called it a planet, but they later called it an asteroid. The term "minor planet" was not introduced until 1841. For a long time, it was considered a subcategory of a planet. In 2006, the IAU held a major meeting to reclassify these bodies. This meeting moved Pluto and other objects into the new category of dwarf planets. An object is called a dwarf planet if it has enough gravity to reach hydrostatic equilibrium. This means it becomes an ellipsoidal or rounded shape.
Tracking these objects requires massive amounts of data. The Minor Planet Center has documented over 213 million observations. There are 794,832 known minor planets in total. Of these, 633,135 remain unnumbered. Only 541,128 have orbits stable enough to receive a permanent official number. Out of that group, only 21,922 have official names.
As discovery speeds increase, the official numbers have grown into six figures. In 2005, the highest number jumped from 99,947 to 118,161.
The naming process follows a strict three-step sequence. First, a newly discovered object receives a provisional designation. This is a temporary code using the year and a code for the half-month of discovery. Second, once the orbit is confirmed to be accurate, the object is assigned a number. It is then a numbered minor planet. Finally, the discoverer may choose to give it a formal name. However, most objects never reach this third stage. Many are simply left with their numbers or provisional codes due to the sheer volume of new discoveries.
Naming conventions have evolved from ancient myths to modern culture. Early asteroids were named after Greek and Roman mythology. Later, people used names of famous people or literary characters. Some names have even been quite eccentric. For example, 2309 Mr. Spock was named after a discoverer's cat. Other names include 6042 Cheshirecat and 9007 James Bond. There is one important rule: you cannot name a minor planet after its discoverer. This is a different rule than for comets. Astronomers sometimes bypass this by naming objects after each other as a courtesy.
Where will your curiosity go next?
🖼️ Images & Media (2)
More to explore
✨ What else?
Related topics you might enjoy
🔬 Go deeper
More advanced topics to explore
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.