Astronomers discover 12 new moons in orbit of Jupiter
– News of July 24, 2018 –
We may think that if we try to discover planets in other systems, it is because we found all that there was to find in the solar system. However, it is a misconception : the objects of the solar system are relatively close but it is sometimes very hard to detect them. For example, the dwarf planet Eris was only discovered in 2005 but it is the size of Pluto. The Kuiper belt beyond Neptune’s orbit is likely to hold many surprises. But there is no need to go that far to measure the extent of our ignorance.
Last week, a team of astronomers announced the discovery of twelve new moons around Jupiter. The planet has been flown over many times and has been visited by two orbiters. However, observations from the earth’s surface have highlighted these moons. The discovery is accidental : the team of astronomers was looking for a massive planet located far beyond the orbit of Pluto, the famous planet 9. But as Jupiter was not far from their field of observation, they took the opportunity to take a look at the giant planet. It took them a year to multiply the observations and thus confirm twelve new satellites of Jupiter. They are not massive moons : they measure between 1 and 3 kilometers in diameter, and most of them orbit at great distance from Jupiter.
Nine of these satellites have a retrograde orbit, that is to say that it revolves around Jupiter in the opposite direction of the rotation of the planet. Astronomers believe that these are the remains of larger bodies that have been pulverized by collisions. They close their orbit around Jupiter in about two years. Two other new moons are closer and follow a prograde orbit. They go around Jupiter in just under a year and could also be fragments of a collision. The second discovered moon is the most curious because it is tiny. Its diameter is less than one kilometer. It orbits in the prograde direction but at a distance that brings it closer to the retrograde moons of Jupiter. This configuration seems unstable and it is surprising that the small moon has not yet been vaporized by collisions. We now know about 79 moons in the Jovian system.
The observations were made from a set of telescopes located on the floor. They demonstrate that it is important not to allocate all our astronomical resources to what is happening outside the solar system. There are probably still many exciting discoveries to be made in the area of gravitational influence of the sun. These are objects that we can hope to explore in the not too distant future. Maybe the European Jupiter Icy Moon Explorer mission will even be able to provide us some clichés.
Image by NASA/JPL/USGS [Public domain], via Wikimedia Commons
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