Titan Is Migrating Away From Saturn 100 Times Faster Than Previously Predicted (phys.org) 42
According to a study published in the journal Nature Astronomy, the orbit of Saturn's moon Titan is expanding at a rate about 100 times faster than expected. "The research suggests that Titan was born much closer to Saturn and migrated out to its current distance of 1.2 million kilometers (about 746,000 miles) over 4.5 billion years," reports Phys.Org. From the report: In the work detailed in the Nature Astronomy paper, two teams of researchers each used a different technique to measure Titan's orbit over a period of 10 years. One technique, called astrometry, produced precise measurements of Titan's position relative to background stars in images taken by the Cassini spacecraft. The other technique, radiometry, measured Cassini's velocity as it was affected by the gravitational influence of Titan. "By using two completely independent data sets -- astrometric and radiometric -- and two different methods of analysis, we obtained results that are in full agreement," says the study's first author, Valery Lainey formerly of JPL (which Caltech manages for NASA), now of Paris Observatory, PSL University. Lainey worked with the astrometry team.
The results are also in agreement with a theory proposed in 2016 by Fuller, who predicted that Titan's migration rate would be much faster than standard tidal theories estimated. His theory notes that Titan is expected to gravitationally squeeze Saturn with a particular frequency that makes the planet oscillate strongly, similarly to how swinging your legs on a swing with the right timing can drive you higher and higher. This process of tidal forcing is called resonance locking. Fuller proposed that the high amplitude of Saturn's oscillation would dissipate a lot of energy, which in turn would cause Titan to migrate outward away from the planet at a faster rate than previously thought. Indeed, the observations both found that Titan is migrating away from Saturn at a rate of 11 centimeters per year, more than 100 times faster than previous theories predicted.
The results are also in agreement with a theory proposed in 2016 by Fuller, who predicted that Titan's migration rate would be much faster than standard tidal theories estimated. His theory notes that Titan is expected to gravitationally squeeze Saturn with a particular frequency that makes the planet oscillate strongly, similarly to how swinging your legs on a swing with the right timing can drive you higher and higher. This process of tidal forcing is called resonance locking. Fuller proposed that the high amplitude of Saturn's oscillation would dissipate a lot of energy, which in turn would cause Titan to migrate outward away from the planet at a faster rate than previously thought. Indeed, the observations both found that Titan is migrating away from Saturn at a rate of 11 centimeters per year, more than 100 times faster than previous theories predicted.
11cm per year (Score:1)
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It's not "nothing", it's 0.00000000011 million kilometers!
According to a very scientific Google search I just did, the average human walking speed at crosswalks is about 5.0 km/h, so it means that if you could walk from Saturn to Titan, it would only take 240000 hours. Or 10000 days. Or 27 years, 4 months and 23 days. But we'll never be able to test this, since nobody can hold their breath for that long.
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Is that the distance from the centre of each planet to the other? Because Saturn is a gas giant so doesn't really have a surface.
In any case walking to Saturn might present other problems as you get closer.
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You will hold your breath after two minutes until forver.
Re:11cm per year (Score:4, Funny)
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0.00000524335 furlongs per fortnight.
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Titan will sweep out about 2000 more Canadian football fields each earth year compared to the year before.
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Given that Saturn's orbital period is 29 years, I doubt that the researchers have been studying Titan's orbit for ten Saturnian years.
11 cm per year?? (Score:3, Insightful)
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Actually that is the most interesting part. How do you detect 11 cm per year change in orbit??? That is pretty remarkable. Those astrometric and radiometric techniques they used must be pretty darn precise.
Re: 11 cm per year?? (Score:2)
I was thinking the same thing - being able to detect 11 cm per year, for a 1.2 million km orbit, is impressive. That's a relative precision (not accuracy) of 1 in 10^10.
Re:11 cm per year?? (Score:5, Informative)
Then they work backwards from that deviation, to back out that it's caused by an ~11 cm/yr increase in orbital radius. If there's something remarkable about the measurements here, it's that they're confident enough about Cassini's position in space to attribute these shifts in position to Titan moving, rather than Cassini not being quite where they think it was and thus e.g. throwing off where Titan is relative to background stars in photos. And that they're doing this using data collected years ago (instead of collected specifically to test this hypothesis), since Cassini was crashed into Saturn in 2017 to avoid possibly contaminating one of its moons with any Earth microbes which may have somehow survived.
Time intervals (Score:2)
Of all measurable quantities, time intervals are usually the quantity that can be measured with the least uncertainty. When designing experiments or making observations, if the measurement of the desired parameter can be converted to a measurement of time, it's usually best to do so.
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They're not measuring a 11 cm/yr increase in the size of the orbit. They're measuring changes in Titan's position in its orbit over the ~13 years Cassini was there.
Okay then, that's still only a difference of 143 cm over the entire measured time period of 13 years, or less than 1.5 meters. By what reference point of a planet is such a measurement made? The average center point of the visual area of the planet? Surely it cannot be a measurement from the surface. It just seems like an incredibly precise and tiny amount of something to be measuring when the objects and their positions are so large.
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They used the occultation of background stars (as seen by Cassini), called astrometry, and changes of Cassini's velocity at each pass, called radiometry, to make the measurements. Each data set was analyzed independently and then compared, and they both showed the same conclusion. Because Saturn is mostly gaseous and liquid Titan's gravitational effect on the planet can set up tides of sufficient power to cause the entire planet to oscillate and set up "resonance locking". This is what can change Titan's
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I'm just impressed that they can measure the distance between two moving planets, one in orbit of the other, with a precision of centimetres.
Sounds like any other unhappy gay marriage, then. (Score:1, Funny)
A Titan running away from another... Or is Titan actually female and this is just a normal breakup after a rough family history?
Alternative name suggestion (Score:2)
Lucen (loosen), after reading
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Well, you know the saying (Score:2)
If you like it then you should have put a ring on it...
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... so many levels of wrong, it's hard to think where to start.
How long? (Score:2)
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It might be a while. First we'd have to transport our spent but mysteriously energetic nuclear waste to the far side.....
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How long until we can build a base on it and ride it out of the solar system like in Space: 1999?
First, we need to come up with a way to stock the base an inexhaustible supply of shuttle craft, because they'll probably get destroyed at a rate of about one per week.
Oort mapping? (Score:2)
Curious is there any initiative to map the Oort halo and outside the solar systemâ(TM)s plane? And does any such map exist beyond âoeHere be dragonsâ? Might be nice to know about perturbing masses... and perhaps something useful could be done using similar techniques?
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There kind of is, it's pretty low priority though since it's so difficult with existing technology. Outer solar system bodies tend to be covered with extremely dark organic molecules which reflect very little of the already-scarce light. There is more work on the Kuiper belt, partly because it's easier but mostly because of the implications of another planetary body at that distance and because they're looking for another target for New Horizons. Most Oort halo objects aren't discovered until they've lef
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Not to mention there's estimated to be around 2 trillion Oort cloud objects. That'll take a while to map.
Push it into Mars.. (Score:2)
It would be cool if you could just push it into Mars, thickening Mars' atmosphere..
Of course that's unrealistic..
Still, if it has even as little as a million years left, it's worth building a settlement there. The gravity is low enough and the atmosphere thick enough that it would make a great place to shoot hydrocarbons and oxygen (from the ice) into space for combustion, propellant, and production of plastics.
I think Tidal forces on the methane lakes should make for some pretty productive energy producin
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It is only "close to" those other places for certain parts of the orbit of Saturn - say one year in 30. For the other 29 years in 30, they are no closer to Saturn than the Earth is, half the time significant distances (half a Saturnian orbital diameter) further.
There are on the order of a trillion Oort cloud objects of a handful of km across each. Their average spacing is comparable to the spacing between the Earth and the Sun.
And that is why... (Score:2)
And that is why you don't put your nuclear waste dumps on the moon.
Eff me... (Score:2)
... immigrants from Titan too?!?
Trump gonna need to build a bigger wall.
Earth's Moon also drifting away (Score:2)
Our own Moon is also drifting away ever so slowly. The average distance per year is increasing by 3.8 cm.
This means that in the distant past, there were no annular solar eclipses, and all were total eclipses. Also means that in the distant future, they would all be annular, and never total.
Read all about it here: Lunar distance [wikipedia.org].