The satellites of Uranus formed inside a giant cloud of steam. This explains the strangeness of their orbit and their relatively small mass, according to a study by scientists from the Tokyo Institute of Technology, published in the journal Nature Astronomy.
The distant cold giants, Neptune and Uranus, are not similar to any of the planets of the solar system – heavenly bodies are located approximately in the middle between gas giants and rocky planets. For example, Uranus rotates on its side – its axis of rotation relative to the orbit plane is rotated 98°.
Astronomers explain this feature by the fact that in the past the planet survived collisions with large objects. Oddities also concern the five satellites of Uranus, Miranda, Ariel, Titania, Oberon, and Umbriel – for example, their orbits are parallel to the equator of the planet, and they themselves are located very close to it, despite their impressive mass.
In a new study, scientists put forward a hypothesis explaining the strange arrangement of satellites. According to the prevailing theory, the satellites of Uranus formed as a result of the same collision, which changed the axis of rotation of the planet. Researchers calculated the consequences of these changes using a model that is used to describe the process of the appearance of the moon.
Modeling showed that the object that Uranus encountered was almost entirely composed of frozen water and other volatile substances that easily evaporate when heated. Therefore, the energy released during the collision led to the formation of a giant disk, it consisted almost entirely of water vapor. Inside this disk, satellites of Uranus formed, the authors of the study believe.