The Earth’s sky is lit by a single natural satellite, the Moon. This has been the case for 4.5 billion years and this should, a priori, not change. But let’s imagine that our planet has inherited several moons. How many of them could we observe in the sky without modifying the orbital conditions of the Earth?
You will also be interested
[EN VIDÉO] Europa, a potentially habitable moon in the Solar System Europa is one of Jupiter’s four main moons. It is home to an ocean of icy water, and scientists believe that life could be there.
Our Solar system has eight planets, as well as a few dwarf planetsas Pluto Where Ceres. But we often forget to consider that they do not travel alone in their continual race around the Sun. Most are indeed accompanied by one or more natural satellites. If the names of some of these satellites are now known to the general public, such as Europe, Ganymede or Titan, their number is however much more important.
Our solar system has more than 200 moons! Almost all orbit around the four gas giants and only three find themselves affiliated with rocky planets. These are our Moon and the two satellites of Mars, Phobos and Deimos. Mercury and Venus have no natural satellites. This striking difference between the two types of planets would however have nothing abnormal, the presence of moons in orbit around a planet being closely associated with the mechanisms of its formation and the processes of evolution of the orbit. Parameters that vary significantly between the small planets rocks and gas giants.
Several moons around the Earth? A physically possible situation
The case of the Earth is however very interesting, since our Planet has a single moon, whose the size is surprisingly large. A characteristic that results from the violent birth of our satellite, following the collision between the young Earth and another protoplanet called Theia.
But could our planet have had several moons? This is the question that researchers have asked themselves. By calculations and modeling digital, the team of scientists focused more specifically on the maximum number of natural satellites that could theoretically orbit around the Earth without modifying the current conditions of orbital stability. If this type of research may seem far-fetched, it nevertheless allows us to better understand the processes of planetary formation in general, but also the gravitational balances of planetary systems.
The results, published in the journal Earth and Planetary Astrophysics, show that the maximum number of moons that can orbit the Earth depends on their own sizes. Our sky could thus be lit, as desired, by seven or eight moons the size of Ceres, four or five moons the size of Pluto, or even three or even four moons the size of our current Moon.
Exomoons still difficult to identify
Impossible to do more without modifying the orbital conditions of the Earth and thus jeopardizing its evolution and in particular theemergence of life. This study thus makes it possible to estimate the maximum number of satellites capable of orbiting a planet without destabilizing it.
The results of this study could thus make it easier to identify the presence of small moons orbiting around rocky exoplanets the size of the Earth. Because, if today the number of exoplanets discovered continues to increase, only two exomoons have so far been identified. Their size, however, exceeds that of the Earth and the planets around which they orbit are of the type Jupiter. But scientists are optimistic: the next few decades should bring their share of new exomoons of smaller sizes.
Pluto and its moon Charon Above and in the background, an image of Pluto (1,185 km radius) in near real colors and in the foreground, bottom right, an image of its main moon Charon (607 km radius) in false colors taken by the New Horizons probe on July 14, 2015. © NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute, CC0
Saturn and its moon Dione Dione is one of Saturn’s moons discovered by Jean-Dominique Cassini in 1684. It was photographed closely by the Cassini probe. © NASA/JPL/Space Science Institute, CC0
Saturn and its moon Iapetus Iapetus is Saturn’s third largest satellite. Iapetus is primarily known for his enigmatic coloring, with one of his hemispheres being particularly bright while the other is very dark. However, some explanations have been offered. © NASA/JPL/Space Science Institute PD
Saturn and its moon Pandora With its 103 × 79 × 64 km, Pandora, one of Saturn’s moons, was only discovered in 1980 on Voyager 1 images. It is seen here on a Cassini image. © NASA, CC0
Saturn and its moon Rhea Rhea is Saturn’s second largest satellite after Titan. It is photographed here by the Cassini probe. © NASA/JPL/Space Science Institute, CC0
Saturn and its moon Titan Titan (5,151 km in diameter) is Saturn’s largest satellite. We see here a recomposed image of the surface of Titan in infrared through its atmosphere seen by the Cassini probe. © Nasa/JPL/University of Arizona/University of Idaho, CC0
Saturn and its satellite Hyperion Hyperion is a mysterious satellite of Saturn with an average diameter of 270 km. Its rotation is chaotic. The image was taken by the Cassini probe. © NASA, CC0
Saturn and its moon Thetys Saturn’s Moon, Thetys, appears in the foreground of this montage of photos taken by the Cassini spacecraft. © Nasa/JPL/SSI/Gordan Ugarkovic CC by-sa 2.5
Mars and its satellite Deimos A view of the Deimos satellite, of Mars, taken by the Mars Reconnaissance Orbiter (MRO). © Nasa
Mars and its satellite Phobos Phobos is the larger of the two satellites of Mars and it is the closest. It is photographed here with a resolution of 7 meters per pixel, by the HRSC camera of the ESA’s Mars Express probe. © Bank of Imágenes Geologicas, CC by 2.0
Neptune and its moon Triton Triton is the largest of Neptune’s fourteen natural satellites, seen at top left in these images taken by the Voyager 2 probe in 1989. There are cryovolcanoes on Triton. © NASA/A. Tayfun Oner, CC0; NASA/JPL, CC0
Jupiter and its moon Callisto Callisto is one of Jupiter’s major moons. It is believed to have an ocean under its surface, it will be studied more closely by the Juice probe. It was photographed here by Galileo. © Nasa/JPL/DLR (German Aerospace Center), CC0
Jupiter and its moon Europa Europa is one of Jupiter’s major moons. It is covered by a global ocean under an ice shelf which is at least a few kilometers thick. Life could exist in this ocean, near hydrothermal vents. The image here is made from photos taken by the Galileo probe. © NASA/JPL-Caltech/DLR, CC0
Jupiter and its moon Io Io, the volcanic, has many active volcanoes. We see, here, an image taken by the Galileo probe. © NASA/JPL/USGS, CC0
The Earth and the Moon Image of the Moon taken by the LRO probe. © NASA, CC0
Interested in what you just read?