Stories
Slash Boxes
Comments

SoylentNews is people

posted by martyb on Friday July 31 2020, @03:11AM   Printer-friendly
from the orbital-enlargement dept.

The Mystery of Titan’s Expanding Orbit:

Seen through the eyes of some omnipotent time traveler, our solar system—like any planetary system—is a heaving, pulsing thing. Across millions and billions of years its contents ebb and flow. Planetary orbits shift in shape and orientation, and billions of ancient asteroidal pieces shuffle through the skeletal disk that defines the major architecture of all that surrounds the sun, itself a star that sheds mass and energy as it gradually climbs an-ever brightening staircase of thermonuclear fusion.

But some things are assumed to be comparatively dull and unchanging. Saturn's largest moon, Titan, for instance, was expected to sit in its orbit with little alteration to that position over the billions of years since its formation. Now a study published in Nature Astronomy by Lainey, et al., has used measurements from the Cassini spacecraft (which orbited Saturn from 2004 to 2017) to determine that Titan has an orbit that grows by an astonishing 11 centimeters each year.

[...] So, what's going on? The answer may be a phenomenon broadly characterized as resonance-locking tidal theory. In essence, if the internals of a planet like Saturn get "strummed" at the right frequency by the gravitational pull of a moon there's an amplification of the tidal distortion—a kind of natural ringing, or resonance, of the thick gaseous envelope of the planet, and consequently more powerful gravitational interaction with the moon that's doing the strumming. And because the internal structure of a gas giant evolves over billions of years (because of things like gravitational contraction and helium rain) these resonances will change over time, sometimes "locking" onto different moons' orbital period and driving unexpectedly fast alterations in their orbits.

Journal Reference:
Valéry Lainey, Luis Gomez Casajus, Jim Fuller, et al. Resonance locking in giant planets indicated by the rapid orbital expansion of Titan, Nature Astronomy (DOI: 10.1038/s41550-020-1120-5)


Original Submission

 
This discussion has been archived. No new comments can be posted.
Display Options Threshold/Breakthrough Mark All as Read Mark All as Unread
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
  • (Score: 4, Interesting) by PinkyGigglebrain on Friday July 31 2020, @05:49AM (3 children)

    by PinkyGigglebrain (4458) on Friday July 31 2020, @05:49AM (#1029157)

    if it was an instrument mis-calibration on Cassini's part then they would have seen the same thing with all the other moons in the system.

    They didn't, and most Astro boffins I've worked with over the years tend to be pretty good at looking for obvious things like instrument mis-calibration or failure issues before publishing.

    It has been said that the most exciting thing you will hear from a scientist is not "Eureka!!", but "that's strange ..."

    This might be another one of those really cool "that's strange" moments that changes our understanding of the solar system.

    --
    "Beware those who would deny you Knowledge, For in their hearts they dream themselves your Master."
    Starting Score:    1  point
    Moderation   +2  
       Interesting=2, Total=2
    Extra 'Interesting' Modifier   0  
    Karma-Bonus Modifier   +1  

    Total Score:   4  
  • (Score: 4, Funny) by FatPhil on Friday July 31 2020, @08:34AM (2 children)

    by FatPhil (863) <pc-soylentNO@SPAMasdf.fi> on Friday July 31 2020, @08:34AM (#1029181) Homepage
    Yeah, but astro boffins also turned the Mars Climate Orbiter into rather pretty martian meteor.
    --
    Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
    • (Score: 2) by Unixnut on Friday July 31 2020, @02:36PM (1 child)

      by Unixnut (5779) on Friday July 31 2020, @02:36PM (#1029306)

      > Yeah, but astro boffins also turned the Mars Climate Orbiter into rather pretty martian meteor.

      A side effect of one part of the astro boffins insisting on not using SI-units, like the rest of the world does. A problem that would not have existed otherwise.

      Saying that, mistakes do happen with complex spacecraft. I remember Cassini having a flaw in its antenna, meaning the Huygens probe was unable to communicate properly on descent (wrong frequency from what I remember)

      • (Score: 0) by Anonymous Coward on Friday July 31 2020, @10:59PM

        by Anonymous Coward on Friday July 31 2020, @10:59PM (#1029514)

        That was no astro boffin mistake. The units used for any part of that mission are irrelevant. That was 100% a systems engineering and test and integration failure. Maybe those failures were the result of upper management budget and schedule pressure, I don't know, but that failure had nothing to do with the units. If one system was expecting one unit and another system was reporting another, checking that stuff is SE and Test 101.