What are Jupiter’s Trojan Asteroids?

Asteroids are small celestial objects which are leftover during the formation of the planets and are orbiting the sun. These asteroids are of different sizes, mass, composition, etc. There is a large number of asteroids located between the orbit of Mars and Jupiter. This area is known as the main asteroid belt. The asteroids located in the main asteroid belt are enormous.

Today, we will explore something new in this article about What are Jupiter’s Trojan Asteroids? So let’s jump into today’s article to answer all your questions.

What do you mean by Jupiter Trojan Asteroids?

The asteroids that share the same orbit as Jupiter around the Sun and are located at Lagrangian points L4 and L5 respectively, i.e., 60 degrees ahead of Jupiter in its orbit or 60 degrees trailing Jupiter in its orbit.

More than 9800 Jupiter Trojan Asteroids are being discovered by May 2021. These Jupiter Trojan Asteroids are more than 1 km in diameter and are more than 1 million in numbers. The first trojan named Achilles was discovered in February 1906 by Astronomer Max Wolf at Heidelberg-Königstuhl State Observatory.

It was followed other many asteroids as listed below by different astronomers at different Observatories. These asteroids were more than 100 km in diameter.

How were the first Trojans discovered?

In 1906, Max Wolf saw an asteroid in an unusual orbit as it remained ahead of Jupiter. He thought that the asteroid was stuck up in Jupiter’s orbit. Another astronomer saw that it was 60 degrees ahead of Jupiter. This reminded them of Lagrange’s statement which stated that if a small space body were to be placed at either of the two stable points in the orbit, the body would remain stationary from the perspective of the planet. This made them realize that the asteroid was stuck up in the L4 point of Jupiter.

How did they get the name Trojan asteroids?

Nearly eight months after Wolf had discovered the first Trojan, another student Kopff discovered an asteroid in L5. Soon after another one in L4. The question was raised as to what to call these asteroids! An astronomer suggested them to be named after characters from the Greek poem The Iliad which was set during the Trojan War.After further discoveries, they were continuously named after the characters. Thus, as a whole, they were referred to as ‘Trojan Asteroids’.

Timeline for Discovery of Trojan Asteroids

Name of Trojan Trojan Discovered On Trojan Discovered By
Achilles February, 1906 Max Wolf
Patroclus October, 1906 August Kopff
Hektor February, 1907 August Kopff
Agamemnon March, 1919 Karl Reinmuth
Odysseus January, 1930 Karl Reinmuth
Äneas October, 1930 Karl Reinmuth
Diomedes August, 1937 Karl Reinmuth
Deiphobus March, 1971 Carlos Cesco and A. G. Samuel
Mentor April, 1984 Antonín Mrkos
ParisMay, 1984 Carolyn and Eugene Shoemaker
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Lucy mission: Where are Trojan Asteroids located?
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Types of Asteroids

There are mainly 3 types of asteroids such as C-type, D-type, and P-type asteroids.

1. C-Type asteroids

C-type asteroids are the most common type of asteroids. C-type asteroids are almost 75% in the amount of all asteroids. The composition of C-type asteroids is made up of a large amount of carbon, in addition to rocks and minerals.

2. D-Type asteroids

D-type asteroids are low in proportion as compared to C-type asteroids. D-type asteroids are made up of organic-rich silicates, carbon, and anhydrous silicates, possibly with water or ice in their interiors. They are found in the outer area of the main asteroid belt.

3. P-Type asteroids

P-type asteroids are low in proportion as compared to C-type asteroids. P-type asteroids are made up of organic-rich silicates, carbon, and anhydrous silicates, possibly with water or ice in their interiors. They are found in the outer area of the main asteroid belt.

How many Trojan asteroids are there?

According to estimates, the L4 swarm is estimated to have nearly 200,000 asteroids of diameter more than 2km while there may be more than 600,000 asteroids of diameter larger than 1km. The L5 swarm contains an almost similar number of asteroids with over 1 million asteroids of diameter more than 1km. The total mass of these asteroids is nearly 0.0001% of the total mass of Earth. but certain reports say these numbers are overestimated and the original number might be significantly lower.

Why doesn’t Jupiter hit the Trojan asteroid belt during the revolution?

The Trojan asteroids move at the Lagrangian points L4 and L5 respectively. That is, they either move 60 degrees ahead of Jupiter or 60 degrees trail of Jupiter. They share the same orbit, and they do not engulf each other as the gravitational force of Jupiter keeps the asteroids in their place.

Exploration of Trojan asteroids

In the year 2017, NASA announced the mission, Lucy, as part of their Discovery programs. It would explore six of Jupiter’s Trojan asteroids. It is supposed to be launched in the latter part of 2021. It will reach the L4 Trojan cloud in the year 2027. Later it will visit the L5 region and explore 617 Patroclus.

Facts about Trojan Asteroids

  • 624 Hektor is the largest known Trojan asteroid. Even then it is just 225 km wide.
  • 2002 CO208 is the smallest known Trojan which was discovered in the year 2002. It is just 6.6km or 4 miles wide. There may be much smaller Trojans than it, but their size is still not known to us.
  • Hektor is only one of two known Trojans to have a companion. It is orbited by Skamandrios which is about 12km wide and revolves at a distance of 625km from Hektor. The other pair is 617 Patroclus which is orbited by Menoetius.
  • One of the targets of Lucy, 11351 Leucus has a rotation period of 440 hours or nearly 18 Earth days. Common asteroids have a rotation period of 2 to 20 hours.


In today’s article, we have learned about different types of asteroids, Lagrangian points, and the composition of asteroids in the main asteroid belt of our Solar system.

I hope you enjoyed this article (What are Jupiter’s Trojan Asteroids?). I was able to respond to all of your queries. Please post any questions or concerns in the comments area below. If you have any queries on Trojan Asteroids or any other issue in the relevant field, please do not hesitate to contact me.

FAQ related to (Jupiter’s Trojan Asteroids)

Q- What are the Lagrangian points?

Ans- Where are Trojan Asteroids located?Trojan asteroids are located either ahead or behind Jupiter at around 60 degrees and share the same orbit.

Q- How many types of asteroids are present in space?

Ans- There are mainly three types of asteroids present in space.

Q- What are the Lagrangian points?

Ans- The points where gravitational forces of two large celestial objects orbiting around the Sun pulls the smaller celestial objects to orbit around the Sun are known as Lagrangian points.

Q- Are Trojan Asteroids dangerous?

Ans- No, Trojan asteroids are not dangerous, as they move either ahead or behind Jupiter at 60 degrees away; hence, there are no chances of being engulfed.

Q- How far is Trojan Asteroids from Jupiter?

Ans- Trojan asteroids are at L4 and L5 Lagrangian points which is almost 60 degrees away from Jupiter in the same orbit.

Q- How did these Trojan Asteroids get their names?

Ans- Each of the Trojan asteroids is named based on Greek Mythology. By convention, after a figure of the Trojan war, these asteroids were named ‘Trojan’.

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