What is a double planet and what are the criteria for its definition? The only double planet of the solar system: a brief description

In this article, we will study the concept and the necessary criteria for a double planet. And we find out which planet can be called the only double planet of our solar system.

Content

Cosmos always attracted his unknown and mystery. And even so far he remains not fully studied. Today we want to touch on such a topic as the double planet of the solar system. We will try to make out this concept and find out if whether there are really double planets in our galaxy.

What is a double planet?

In astronomy, a double planet is a binary system in which both objects have a satisfactory planetary mass for the gravitational effect. This concept is also known as a binary planet.

But this term not recognized by the International Astronomical Union And, therefore, it is not in the official classification. In 2006, the Union of Scientists in the field of astronomy from all over the globe was made and put on consideration an amendment on the classification of such astronomical bodies.
This change also concerned the fact that the Pluto-Haron system was designated as a double planet. But this proposal was rejected in favor of the current position of the planet.
In the advertising materials advertising the Smart-1 mission, one of the most popular space research centers around the world once even referred to the Lun Earth system, as a double planet. But the information shown in the video does not quite correspond to reality.
Many binary asteroids with objects, approximately the same in mass, are sometimes unofficially called double small planets. These include binary asteroids 69230 Hermes and 90 Antiope.

The double planet has no official status

What criteria are defined by the "double planet"?

There are debates between scientists regarding what criteria should be used to distinguish the “double planet” from the “planetary moon system”.

Both bodies satisfy the criteria of the concept of "planet"

The definition of a double planet requires that both bodies individually meet the criterion of the orbit cleaning to be called a double planet.
They must also have sufficient gravitational force above the star around which there is a rotation.
And for this you need the proper mass of the space body.

The ratio of the masses of objects is nearing 1/1

One of the important characteristics when determining the “double planet” is the ratio of the masses of two bodies. The mass ratio of 1/1 will indicate the bodies of approximately equal mass.
Therefore, using this criterion, satellites of Mars, Jupiter, Saturn, Uranus and Neptune can be easily excluded. All of them have masses less than 0.00025 (1/4000) from part of the planets around which they rotate. Some dwarf planets also have satellites much less massive than dwarf planets themselves.
The most noticeable exception is the Pluto Haron system. The mass attitude of Haron to Pluto is 0.117 (≈ 1/9), which is practically approaching 1. Therefore, Pluto and Haron were described by many scientists as “double planets”. But at the end of 2006, in connection with the clarification of the concept of the meaning of the “planet”, they were categorized in the “planets of the double dwarf”.
Mas at the present moment calls Haron a satellite of Pluto, but clearly expressed his readiness to reconsider this classification in the future.
The mass attitude of the moon to the ground is slightly larger - 1/81, which is also noticeably close to 1, in comparison with all other ratios of satellites and their planets. But from the mathematical side - this is still more by 2! Although some scientists sometimes attribute the Earth and its companion to this category. And, perhaps, this is a reflection of a mistaken commercial.

Earth and moon are sometimes also attributed to this category, but still the ratio of the masses is closer to 2

The location of the center of the mass

Currently, the most commonly proposed fixing for a double planet system is an aspect with a barcenter around which both bodies are located. It should lie outside the surface of both bodies. In accordance with this definition, Pluto and Haron are a double planet, since the center of mass is outside Pluto.
It is interesting to note that the center of the mass of the system of the Jupiter Sun lies outside the surface of the star. But the statement that Jupiter can be a double star is not similar to the assertion that Pluto-Haron is a binary planet. The problem is that Jupiter cannot be called a star or even brown dwarf. This is due to its low mass and the inability to maintain any type of merger.

System formation

The final consideration is a way in which these two objects came to the creation of the system. It is assumed that both the Earth-moon system and Pluto-Haron were formed as a result of giant blows.
The second body influenced one body, as a result of which, a disk of garbage was formed and two new bodies formed through accretion. There is also a version that one new body has formed, while a greater body remained, but has changed.
However, a gigantic effect is not a sufficient condition for both bodies to be a “double planet”. Since such an effect can also lead to the creation of small satellites, for example, 4 small external satellites of Pluto.
Now an abandoned hypothesis about the origin of the moon was actually called the "hypothesis of a double planet." The idea was that the Earth and the Moon formed in the same area of \u200b\u200bthe protoplanetary disk of the solar system, forming the system during gravitational interaction.
This idea is also a problematic condition for determining two bodies as “double planets”, since planets can “capture” space bodies through gravitational interaction.
- For example, satellites of Mars (Fobos and Deimos) are considered asteroids that have long been captured by Mars. Such a weak definition would also consider Neptune-triton a double planet. After all, Triton was a body of the same size and a similar composition with Pluto, but later was captured by Neptune.

The only double planet of our solar system: a brief description

The NASA space telescope (ESA Hubble) received the brightest photos of one of the most remote and mysterious objects of our solar system - Planet Pluto.

Observations were made using a camera with a distorted image of a European space agency. This is the famous ninth and last real planet until recently. Pluto is also the only planet that the aircraft did not visit.
Pluto was discovered almost 90 years ago by the American astronomer Claid Tombo (in 1930), which was looking for a source of irregularities observed in the orbit of Uranus and Neptune. Since then, it became obvious that Pluto is a very peculiar object.
- Its orbit is inclined and more elliptical than the orbit of any of other planets in the solar system. Pluto also rotates upside down, with its northern pole below the plane of our star system, in the opposite direction from the movement of the Earth and other planets around the sun. Pluto is less than our moon, as well as denser than any of its neighbors in the solar system. If we take into account the ratio with body weight.
But, perhaps, his most amazing property was discovered exactly 40 years ago (or rather, in 1978). This is an amazing characteristic of Pluto - a huge satellite called Haron, which was seen in ground photographs. Subsequent studies have shown that Haron is approximately half the size of Pluto, which makes it the largest famous satellite relative to its planet throughout the solar system.

The only dual planet in our solar system

In fact, because of this, Pluto is often mentioned as a double planet. The rotation period of the Pluto Haron system is only 6 days. Currently, Pluto is located near his closest approach to the ground, in his 249-year journey through the solar orbit. The distance between Pluto and Earth is now approximately 4.5 billion km. This allows scientists to study Pluto and Haron, receiving high -quality pictures from satellites.
A detailed analysis of changes in the brightness of the two planets will ensure that extensive information about their surfaces and atmospheres that cannot be obtained from the Earth will ensure. Exact measurements of the parameters of the orbit of the Pluto-Haron system are also possible. This will allow astronomers to measure the individual masses and density of two objects, thereby ensuring the receipt of important keys to the study of their origin.
One of the possible ways of the appearance of a double planet is that objects similar to Pluto and Haron were created in huge quantities in the external areas of solar nebula. But most of these "planetary embryos" were either supplanted from the internal solar system or absorbed by giant planets.
- Namely, such icy giants as Jupiter, Saturn, Uranus and Neptune. Only Pluto and Haron survived independently, and to this day they remain like that. The continuation of the monitoring of these two exciting objects on the edge of our solar system may help astronomers understand the nebula, from which all planets were originally formed.

Now they are closest to the ground, which allow the scientists to learn more — Now they are relatively close to the ground, so the scientists can study them

We can come to the final conclusion

Theoretically, if there is a double planet where one component is 1% more than the other, we will still call them a “planet” and “satellite”. Moreover, there is no clear lower limit, as much as a massive satellite should be more than a relatively small body, so that the system is considered a “double planet”.

Pluto and Haron They have a ratio of 1/9 (from the mass of Pluto), which, of course, are a double planet. Although Pluto was disqualified from a number of large planets, so this title was in question. There is a version that the scientists will change their opinion.
Many ordinary people and even scientists consider Earth and moon also a double planet, since there is a coefficient of 1/81 from the mass of the Earth. But this is an erroneous opinion. So far there is no evidence and official theories that this is not a satellite and planet.
And, in general, the definition of a double planet has only supposed requirements and criteria. Perhaps, as soon as some extra -annual planets with approximately the same satellites or moon are found, the term “double planet” will be determined more strictly. But while he has unofficial status.