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The moon Saturn , is Titan , is a strange place: larger than the planet Mercury, this satellite is wrapped in a thick atmosphere -the only one that has a around the Solar System – covered rivers and seas of liquid hydrocarbons, such as methane and ethane. Below this layer, there is a thick crust of ice . Below, scientists believe that it hides a ocean of liquid water . And many suspect that there may be some kind of life.
But their features do not end here, and a recently published study in “Nature ” Astronomy” reveals a new question: Titan walks away from Saturn much faster than the scientists thought. As fast as 100 times more than expected -to the “frenetic” pace of 11 inches per year- , which means that his birth occurred much closer to what is currently ( 1.2 million kilometers of distance ) and that started her journey a few 4,500 million years .
“most of the previous work had predicted that the moons like Titan or Callisto -moon of Jupiter – is formed at a maximum orbital distance similar to where we see them now,” explains Jim Fuller , assistant professor of theoretical astrophysics at Caltech and a coauthor of the new article. “This implies that the system moon of Saturn, and it is likely that also rings , to be formed, and so most dynamic of what was previously believed”.
Similarities and differences of the Moon, and Titan.
To understand the basic concepts of the migration of the orbits, we can look to our own Moon. She exerts a small gravitational attraction on us while we orbit. This is what causes the tides: the jerking rhythms of the satellite, make the oceans of the Earth are abulten from side to side. But the effect does not end there: the processes of friction within the Earth become a part of this energy in heat , by distorting the gravitational field of our planet, and “pushing” to the own Moon forward in its orbit . This makes our satellite gain energy and move away gradually, at a rate of approximately 3,8 centimeters per year . However, this process is really gradual and both bodies will be swallowed up by the Sun within about 6,000 million years before the Moon is set to wander alone through the universe.
Titan exerts an attraction similar about Saturn, but the processes of friction within Saturn are generally considered to be weaker due to the composition gaseous planet . Standard theories predict that, due to his distance from his ruling planet, Titan should be migrated to a slow pace of at least 0.1 centimeters per year . However, the new findings contradict, and in many ways, this prediction.
Two teams, two tools
The two teams of researchers who participated in the work used a different technique to measure the orbit of Titan during a 10 year period . One technique, called astrometry , produced accurate measurements of the position of Titan in relation to the background stars on images taken by the Cassini spacecraft. The other technique, the radiometric , he measured the own speed of Cassini, as it is affected by the gravitational influence of Titan.
“By using two sets of data are completely independent, astrométricos and radiometric, and two different methods of analysis, we obtained results that are in tune,” says Valery Lainey , first author of the study and who previously worked for JPL, NASA, but is now located in the Observatory of Paris, University PSL.
11 inches per year
The results are also in agreement with a theory proposed in 2016 by the Fuller, who predicted that the rate of migration of Titan would be much faster than the theories of tides standard estimated. His theory points out that it is expected that Titan will boost gravitationally with Saturn with a particular frequency which makes the planet oscillate strongly, something like how is balancing the legs on a swing at the right time to propel them higher. This process of tidal force is called blocking resonance. Fuller has already proposed that the high amplitude of the oscillation of Saturn would dispel a large amount of energy, which in turn would make that Titan walks away at a faster pace than previously thought. In fact, both observations found that the satellite migrates to the incredible speed of 11 inches per year.
“The theory of the locking of resonance can be applied to many systems astrophysicists. We are now investigating if the same physical process can happen in star systems binaries or systems of exoplanets,” says Fuller.