The earth can be “the Solar system lost exoplanet”

Still quite recently we thought that our Solar system is a prototype on which also other planetary systems have to be built. We thought that there are two classes of planets: the firm worlds which we find grouped in internal areas, and gas giants which are far away. Since 1990th years we have begun to find planets and near other stars, and then have found out that our Solar system not absolutely normal. In new work which has been taken over to the publication this week two astrophysicists from Columbia University have made an attempt to find out why so.

It appears, to have small firm planets in internal solar system and big gas giants in external, not absolutely normally. Gas giants and firm planets can be found everywhere, and in large planets exactly the same chances to be closer to the star, as well as at small. Planets which we found have shown that nothing forbids gas giants to become “hot Floodlights”, it is even more — they act this way quite often. The second surprise surprises even more, and it is worth thanking for it innovative work of space observatory of Kepler of NASA. Though the firm worlds of the size of Earth — more largely, and less — are as widespread as the worlds of the size of the Neptune and Jupiter, are also the third class of planets, the most widespread of all. Between the sizes of Earth and the Neptune there is an option which we have missed: exoplanet (or mini-Neptune). And as it has appeared, суперземель it is more, than any other planets.

The first question which at us arose: why this class of the amazing worlds such densely inhabited? But as our models of planetary educations near stars improved, we began to see that together with the surviving planets also smooth distribution appears. The worlds which were too little massive, as a rule, were absorbed, jumped out or abandoned in the Sun with other bodies. In process of increase in mass of the planet also the probability of their survival increased. The massivny the world — it is desirable, three times massivny Earth — the more probably that its gravitational attraction will envelop it hydrogen and helium. These worlds with an intermediate weight shall be somewhere between firm planets and gas giants. But if you look for more and more massive worlds, you will see what them becomes less and less. The Universe doesn’t produce the excessive number of the massive worlds just because it has raw materials. For formation only of one Jupiter at it would leave our 317 planets.

As our understanding of planetary education improved, at us matters of substance began to appear. If exoplanet were the most widespread type of the worlds, what such special in the Solar system what we have no exoplanet? Options are interesting, but disappointing:

Young exoplanet were created, but didn’t survive, perhaps, were thrown out together with migration of huge planets.
All internal Solar system was formed before Jupiter moved outside, and the firm worlds were small because were created late when all material was already spent.
Our massive gas giants and the Sun grabbed the first planetoobrazuyushchy material, without having left to a exoplanet and chance.

However using the latest developments in the field of probabilistic forecasting, scientists Chzhinchzhin Chen and David Kipping came to a new, interesting and complete explanation. Perhaps, we very much were mistaken.

In most cases, when we watched planets, we knew either the weight, or radius, but not both parameters at the same time. But without knowing one parameter, it is impossible to understand with what world we deal, with firm like Earth or with gaseous like the Neptune. Provide two absolutely different worlds, each of which three times massivny Earth: one has a firm kernel in 2,8 terrestrial weights with a thin cover of gas around, and at another a firm kernel in 1,5 terrestrial weights and as much gas in the atmosphere. The first planet will be similar to Earth, but in practice is exoplanet: it is more, massivny and with the thin atmosphere. The second planet will be more similar on the mini-Neptune: 10 000 kilometers of “atmosphere” over a firm surface in all directions, and pressure upon surfaces will instantly crush any life known to us.


Conclusions of Chen and Kippinga allow to draw precisely line between exoplanet and the mini-Neptune. They have submitted the scheme of classification which much more surpasses our previous awful estimates. Their option:

Any world, weighing less than 2,0 ± 0,6 terrestrial, most likely, will be firm.
Any world between 2,0 and 130 terrestrial masses will resemble on the Neptune.
Everything that the massivny 8% of our Sun, will be a star.

That’s all. Other classification, according to astrophysicists, will be utter nonsense.

Also it says to us that the majority of the worlds which we call “exoplanet” are actually located on the low-massive end the neptunopodobnykh of the worlds that confirms old suspicion. For the planets found a transit method, the firm world weighing 2,0 of terrestrial will be about 25% more in a radius, than Earth; if it is more, then it almost for certain will be the neptunopodobny world with a massive hydrogen-helium cover.


Also you know why in our Solar system isn’t present any exoplanet? Because weighing 50% and 40% from this transit threshold, respectively, Earth and Venus are just those exoplanet which we look for: firm planets with a big weight. Following “class” of planets will be the neptunopodobny worlds, and we have three such.

“The large number of the found planets weighing 2-10 terrestrial is often given as the proof that exoplanet are very widespread also our Solar system, it turns out, is unusual”, authors of work write. “However if to shift border between the worlds of terrestrial and neptuniansky type up to 2 terrestrial masses, the Solar system won’t be unusual any more. By our definition, only three of eight planets of Solar system are the neptuniansky worlds which are the most widespread type of planets near other stars of solar type”.

In other words, the fact that in our Solar system there are no planets between two and ten terrestrial masses is right, and this in itself is a rarity. But it is not the best way of classification of planets; they just enter range the neptunianskikh of the worlds, and we have three such. Then we absolutely incorrectly considered a problem of missing суперземель. If it is correct to consider her, interesting a conclusion will be two: the fact that we called exoplanet, at all to Earth not probably, and there is no problem any because nothing vanished in our Solar system.

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