Hot Neptune

Under a Hot Neptune refers to a planet on the type of smaller gas planets like Uranus or Neptune, but which, unlike the equivalents mentioned move on a much closer orbit around its sun. Such planet been hypothetically, they have not yet been discovered.

Theoretical construction

In essence, such planets as the smaller gas giants in our solar system will be constructed. However, there is in the outer atmosphere, a correspondingly higher temperature to the lower layers such as the gas of the solar gas planet have a high pressure and intense heat. It is conceivable, a rock and ice core at a pressure of about one million bar and a temperature of 7000-9000 Kelvin. This would be surrounded by a sheath of various compounds, which is, depending on the mode of origin of the planet to volatile substances such as ammonia, methane or water or heavier compounds ( various salts ) is (see creation ). The outer layers of such a planet existed on parts of hydrogen and helium, but their share in the atmosphere would probably be lower, since the proximity to the Sun and the associated high temperatures would lead to a partial volatilization of these light gases despite the high gravity of the gas giant. A " abrasion " of lighter materials through the at short distance from the star relatively strong solar wind will probably prevented due to a strong magnetic field through the jacket.

Formation

About the possibilities of the formation of a hot Neptune there are two theories. Firstly, it is believed that he has become such a hot Jupiter formed according to common opinion in the outer regions of the solar system instead of first rotated on an elliptical orbit in a spiral ( for example Ausbremsung by dust ). This brought him closer and closer to its sun until it either sometime but still moving on a stable path or fell into the sun. The other theory is that the planet has already formed near the sun. So far there is not a hot Neptune was observed, these theories could not be verified. In the latter case would the planet from heavier materials, as these opposed to the more volatile can also condense at high temperatures and are more influenced by gravity fields, while light compounds are expelled from the solar wind, even before they can be absorbed by a sufficiently massive planet. It would be conceivable an atmosphere of sulfur compounds or silicate vapors. Is a Hot Neptune, however, originated in the outer areas, it contains a higher proportion of volatiles, which would be detected spectroscopically at a transit of the celestial body. It is also possible that a hot Neptune has formed from a hot Jupiter, which gradually loses its mass in too large perihelion. In this case, a hot Neptune a transitional stage between a Hot Jupiter and a terrestrial planet dar.

Possible candidates

In the following extrasolar planets it might be to hot Neptunes: Gliese 436 b and c 55 Cancri e and c HD 149026