"I despise the Lottery. There's less chance of you becoming a millionaire than there is of getting hit on the head by a passing asteroid." - Brian May
Asteroid family
When we hear the word family, first of all we think of our parents. Then there are siblings, grandparents, grandparents, and other relatives. Our behavior is usually the same as our family. "Identity of the clan in use," he says. Sometimes you may be told that you look like your father or mother or grandparents. So much for the match on the outside গেল The similarity on the inside is not less. Mainly similarity of genetic traits. Again, our bodies are made up of the same elements. Etc. Various matches can be found.
The time is 1919 Kiyotsugu Hirayama, a Japanese astronomer, noticed that some asteroid features had many similarities to those of other asteroids. For example, the "semi-major axis" of their orbit, the inclination of the orbit (it must be understood a little ৷ this means how much the object of one context is tilted to the other object relative to the orbit. Imagine you are walking a certain distance around your friend. There's a bird spinning around your friend now. The bird is spinning a little at an angle to you. Suppose the bird went over his left hand and came out with the bottom of his right hand, that is, tilting the orbit of the bird. The question may arise, why are some of the planets in the solar system visible in the sky when all the planets in the solar system are in a simple position? That is, the characteristics of the asteroids he observed are almost the same. He then decided that the origin of these asteroids was probably the same and later decided to group such asteroids separately. However, since then they are separately included in the Asteroid Family. At present the number of asteroid families is about 20-30 and about 33-35% of the asteroid belt belongs to one family or another. Moreover, there are some more families who are yet to be tested. We will discuss different asteroid families. But first let's talk about how they originated.
Origins and consequences of the asteroid family
At the core of the asteroid family is the collision of asteroids with asteroids. We can imagine the two images separately.
In the first image, the collision is so strong that the asteroid struck by another asteroid as a result of the collision completely crushes the injured asteroid. This injured asteroid is called the patent body. The family is named after the mother's body. It can, of course, be in two ways. If the two asteroids are roughly the same size or the one that struck is at least larger in size than the one that was hit, it could break and crush the other. As a result we find relatively small asteroids in this figure. That is, the family members of asteroids born in this way are smaller in size.
On the other hand, in the second figure, the hitting asteroid will be smaller than the maternal body or the injured asteroid. In short, they will not be so heavy that the mother-asteroid is completely crushed as in the first image. This means that the maternal body will be larger and a very large abyss will be formed by the impact of the hitting asteroid, as well as the small rock-shaped material will be scattered from the body of the maternal asteroid into space as a result of the injury. And as a result we get a big asteroid and some small asteroids around it. This means that the asteroid family born in this way has a large asteroid and the rest are relatively small.
However, asteroid families do not exist forever. It can be said that their life span is fairly specific. Up to about a few billion years. Like the other asteroids discussed earlier, their orbits are changed by the gravitational force of various planets, especially Jupiter and some other asteroids. As a result, at one point a member of the asteroid family is forced to leave the family.
Conflict also plays an important role in this. Often members of an asteroid family collide with each other. Again, it often collides with an asteroid outside the family. This breaks down the asteroids in the family and makes them smaller. As a result, they fall into one of Jupiter's resonances as a result of a solar storm or the Yarkovsky effect. As a result, like the asteroids discussed earlier, they also departed from the asteroid belt.
Scientists need to be careful not to use unauthorized practices when determining the members of the asteroid family. In particular, there are some asteroids whose orbits often coincide with the orbits of a single asteroid family. It may seem like it's a family member, but it's not. So how can these fake members be separated? This is why we see the chemical elements of the asteroid. Although there is a similarity in orbit, since the source of the fake member is not the same asteroid, it is normal that the chemical composition of the member of the asteroid family does not match with it. And this is how they are pruned. These are called interlopers.
Different asteroid families
Of course, I mentioned a couple of asteroid families earlier. Now we will get acquainted with several asteroid families.
First let's get acquainted with the Flora family. These are S-type asteroids. They are located in the innermost circle of the asteroid belt. They orbit the Sun at a distance of 2.15AU and 2.35AU. Their inclinations range from 1.5 ° to 8. About 4-5% of asteroids in the asteroid belt are members of this family. The most prominent member of this family is the flora asteroid. It is the largest asteroid in the family with a diameter of 140 km and 60% of the mass of the whole family.
Another famous family is the Vesta family. The Vesta asteroid itself is one of the most famous asteroids. The semi-major axis of this family ranges from 2.25AU to 2.5AU and the inclination is 5 ° -6. This family is bigger than the Flora family. About 6% of asteroids in the asteroid belt are members of this family. Remember the second picture of the birth of the asteroid family? This family is an example of that. This family was created after the Vesta asteroid hit. The crater formed by the injury is located in the south pole of the Vesta asteroid.
In the innermost circle is a small family named Naisa. Their orbits are almost equal to Vestar. But Nati is less than Vesta family. Their inclination is more than 1 কিন্তু but less than 5.
I talked about Hestia Gap when discussing the Cricketwood Gap. Behind this gap live two asteroid families. One is called Unomia and the other is Gefion. These are two influential families in the middle circle. The asteroids in the Unomia family are S-type. Of the two, it is the most influential. The family is named Unomia asteroid. About 1.4% of asteroids in the asteroid belt belong to this family. They have a semi-major axis range of 2.5AU-2.6AU and a slope of 11-18. The Gafion family's semi-major axis range is 2.6AU-2.8AU and the slope is more than 8.5 কিন্তু but less than 18. About 5% of asteroids in the asteroid belt are members of this family.
Remember the fake member? What about interlopers? The Gaffian family is a good example of this interloper. It was this family that told scientists that the family should not be included just by looking at orbital issues. Our popular asteroid Ceres is located in the orbit of this family. But, the chemical composition of Ceres and Geffion is completely different! So we are sure that their source is also different.
I discussed some of the families inside and outside the asteroid belt. Now let's talk about some of the families in the outer enclosure. In the outer enclosure we see the Coronis, Eos, Themis, and Heizia families.
The Coronis are also called the Lecrimosa family They have a semi-major axis range of 2.8AU-2.95AU and a slope of 0-3.5.
The distance of the Yose family is 2.99AU-3.03AU and the inclination is 8-12.
The Themis family has a range of 3.08AU-3.24AU, and is said to be located near the end of the main enclosure. Their inclination is below 3. The location of the Haijia family is also here, but their descendants are higher than Themis. Moreover, Hijia itself is one of the big asteroids
At the very end, the Hungarian family met. Their semi-major axis ranges from 1.7AU to 2.0AU They are again very close to the 4: 1 resonance of Jupiter. It is the densest family in the solar system. The orbits of asteroids near the 4: 1 resonance are strongly influenced by Jupiter, and we have discussed their consequences in the Creekwood Gap episode.
Again, if the inclination of the asteroids in this 4: 1 resonance is low, it is also very much influenced by Mars. If the inclination is high, it does not have much effect. However, with less inclination, Mars pushes them out of orbit. As a result, only more asteroids remain. The grandson of the Hungarian family is 18 ° -34. This family is thought to be worthy after Vestar as the source of a special and rare meteorite called Aubrite. That is the best candidate.
The location of the Sibyl family just outside the main enclosure. Their semi-major axis is between 3.27AU-3.8AU and the slope is less than 25. This family is named after the asteroid Siebel. It is believed that its maternal body was large. The members of this family are mostly C-type and X-type.
In other words, the astronomer Kiyotsugu Hirayama, the father of the asteroid family concept, was able to determine the five asteroid families himself, Flora, Marina, Coronis, Jos and Themis. So these 5 asteroid families are collectively called "Hirayama family" after him.