The moon, as you know, is far from the onlysatellite in our solar system. So, if there was a competition between the planets for the title of best satellite, then the Earth and the Moon would hardly have won. The fact is that the gas giants Jupiter and Saturn together are proud owners of more than 150 moons: 82 natural satellites revolve around Saturn, and Jupiter is surrounded by at least 79 celestial bodies. Agree, the choice is not easy, but Titan must be in the top three - the largest moon of Saturn, on which there are methane rivers, lakes and seas. This is a special satellite that, as scientists recently found out, is moving away from its home planet 100 times faster than previously thought. But why?
The genius of prose and science fiction Kurt Vonnegut inin the novel “Titanium Sirens” he wrote about this moon as follows: “The air of Titan can be compared with the air that happens on Earth on a spring morning near the bakery’s door overlooking the back patio.” Unfortunately, there is no air and bakeries on Titan, but we still do not want this amazing satellite to disappear. Unfortunately for us, this chaotic world is moving away from its host planet 100 times faster than astronomers originally assumed.
Using data from the NASA Cassini mission, the groupScientists from the Jet Propulsion Laboratory (NASA) made an amazing discovery that showed that in the past, Titan was much closer to Saturn and that the entire system of 82 satellites is expanding faster than previously thought. The results are published in the journal Nature Astronomy and, according to Inverse, add even more questions about the age of the Saturn system and how its moons were formed. It is believed that 4.5 billion years ago, when the Solar System was born, the satellite of Saturn was much closer to the planet, but over the years it migrated to a distance of about 1.2 million km from the gas giant.
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Why do moons migrate?
All moons move away from planets around whichrotate. Even our Moon is slowly moving away from the Earth, drifting 3.8 centimeters every year, which is why the length of the day is gradually increasing. But for us to notice this, millions of years must pass. Note that all satellites are formed in different ways. Some were formed simultaneously with the host planet as a result of the collision, others once plowed the space in the form of stones, but were subsequently captured by the gravity of Saturn.
The force of gravity of the gas giant, along withgravitational attraction between the moons, keeps satellites in orbit of the planet. However, over time, the satellites move farther and farther away from the receiving planet. This is due to the fact that the gravity of the satellite, no matter how small it may be, causes tidal phenomena on the central planet.
Today, astronomers are aware of the existence of 82Saturn’s moons. It is believed that planets with such a huge number of natural satellites will “push out” their external satellites, such as Titan, much more slowly than satellites in internal orbits, since they are farthest from the planet’s gravitational attraction. However, the results of the new discovery suggest that external satellites can be moved further away by the host planet at the same speed as the internal moons.
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Titanium is a special moon
To measure the migration speed of Titan,researchers tracked the position of the satellite in images captured during NASA's Cassini mission. The data obtained were then compared with the radio waves that this spacecraft sent to Earth in the period from 2006 to 2016. By the way, by tracking the change in the frequency of the radio wave signal in 2019, scientists made a detailed map of the evolution of the Titan’s orbit, as my colleague Daria Yeletskaya spoke in detail about.
Cassini launched on October 15, 1997 and entered orbitSaturn June 30, 2004. During its 20-year mission, the spacecraft made nearly 300 revolutions around the gas giant and took more than 453,000 images, sending 635 gigabytes of data to Earth.
Since the mass of Saturn is significantly superiorthe mass of Titan, and in a gaseous medium in the bowels of Saturn, the friction caused by the tide is lower, it was assumed that Titan is moving away from its planet more slowly, no more than 0.1 centimeter per year. But using two independent data sets - astrometric and radiometric - and two different methods of analysis, astronomers obtained results according to which Titanium moves away from Saturn at a speed of 11 centimeters per year - almost three times more than the external migration of our moon.
You will be interested: Everything that you wanted to know about the methane lakes of Titan, but were embarrassed to ask
The authors of the study also note thatthe results obtained for Titan and five other satellites are consistent with previously obtained data, as well as with the theory proposed in 2016 by Jim Fuller, an employee of the Department of Theoretical Astrophysics at California Technical University. He predicted that the Titan’s migration rate would be much faster than standard theory suggests, since the moon causes tides on Saturn at a certain frequency. It also suggests that Titan formed much closer to Saturn, but with the passage of time migrated to its current position.