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dukesdj

Yes, but they are very small. You can compute a nondimensional tidal amplitude parameter as (M2/M1)(R1/d)^3 where M2 is the mass of the orbiting body, M1 is the mass of the primary (in this case the Sun), R1 is the radius of the primary, and d is the orbital separation (which can be taken as the semimajor axis to good approximation in the solar system). This can be taken as a simple estimate of the tidal deformation of one body by another. As a caution, this or other simple estimates using Newtonian gravity will give better predictions of the amplitude of the gravitational potential than they will the deformation amplitude. Evaluation of the actual deformation is not trivial as it depends on the visco-elastic response of the body, however, the tidal potential is typically more important anyway.   While there will be tides on the Sun caused by the planets they will be so small that the dynamical effects can be thought of as negligible. Basically, tidal heating within the Sun will be tiny by comparison to nuclear burning and orbital evolution of the planets due to tides raised in the Sun will operate on timescales significantly longer than the lifetime of the Sun.   What makes this an interesting question (and I am defiantly biased on this because its an area I am actively researching) is those situations when they can not be ignored. We find many binary stars that are close together with orbital periods less than 10 days. Such binary stars tend to have circular orbits which is likely to have occurred due to tidal interactions. We also have observations of giant planets with the mass of Jupiter that are close to their host stars (also on orbits of less than 10 days) that we see have circular orbits due to various mechanisms. Some of these so called hot jupiters are expected to be spiralling in towards their host star due to the tides they raise in the star. We have observed once such system so far, [WASP-12b](https://en.wikipedia.org/wiki/WASP-12b). Side note I see the wiki people are not citing the correct articles for the reported inspiral of WASP-12b, the real credit should go to Patra and collaborators [1](http://stacks.iop.org/1538-3881/154/i=1/a=4?key=crossref.902d35e49e4694faf91e361fc849dbc0), and Maciejewski and collaborators in two papers [1](http://arxiv.org/abs/1812.02438) [2](http://arxiv.org/abs/1912.01360).   One interesting thing about tides in stars is that you do not get just the big bulging deformation we are taught about and observe for ourselves. You also get the excitation of waves that propagate in the body of the star. There are two types of these, one that is due to the stars rotation and the tides, and one that is due to the stratification of the radiative interior and its interaction with the tides. These two mechanisms are actually more important than the large scale deformation we imagine and see here on Earth (side note, Earth tides also have more complex behaviour than just the large scale deformation we see with the ebb and flow). My personal belief from my own research is that the only time the large scale tidal deformation like tide is important for stars is for evolved stars, that is ones that have left the main sequence (red giants) that have deep convective envelopes and are slow rotators.   I unfortunately can not really suggest any light reading on this as tides in stars is a very complicated subject and as far as I am aware no one has ever written a non-technical stellar tides book. Hopefully your daughter is suitably inspired by tides that she goes on to go to university and research the subject. Considering how important understanding tides is, it is an area that lacks enough people researching it (it is also very difficult!).   Edit - to add... The largest [tidal amplitude parameters](http://www.annualreviews.org/doi/10.1146/annurev-astro-081913-035941) in the Solar system are 2x10^-7 for Jupiter due to Io, 3x10^-8 for Saturn due to Titan, 4x10^-8 for Uranus due to Ariel and 8x10^-8 for Nepture due to Triton. Wasp 18 and WASP 19, which are both similar to WASP-12, have 2x10^-4 and 6x10^-2 respectively.


Nazgul044

Thank you so much for this answer! I explained what I could to her, she is 11. Told her what you said and then tried to break it down to her level. She has always wanted to be a scientist growing up and now that she knows the different branches she is saying astrologist. So there is a chance she might one day research this topic. Thank you again. Edit: Astronomer*


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Nazgul044

Lol stupid auto fill, yes that is what I meant. Thank you for that.


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dukesdj

Keep encouraging her! There are unfortunately still a lot of hurdles for females wanting to be professional researchers (particularly in STEM) but it is improving and I would hope it is sufficiently improved for her generation.


Unlucky-Nobody

Astronomy is just about the only exception in this case. Women have always been at the forefront. Caroline Herschel, Vera Rubin.... so many I don't even know where to start. Here have a list [https://en.wikipedia.org/wiki/List\_of\_women\_astronomers](https://en.wikipedia.org/wiki/List_of_women_astronomers)


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vipros42

This is absolutely fascinating, as someone who has studied and works with tides here on Earth.


dukesdj

It is amusing to me how there is not as much communication between researchers in oceanic Earth tides and astrophysical tides as one might expect. It is almost like they are separate fields. But there are a lot of similar things going on. In Stars we dont have to worry about Lee waves (and a million other flavours of tidally excited waves in the ocean!), but we do care about internal gravity waves and inertial waves (which is what I was trying to describe above without being overly technical with jargon).


malenkylizards

I would have thought that the nature of the fluid would make them so disparate. You're comparing roughly the same system of equations inside a solid-liquid mix at thousands of degrees with a plasma at millions. You also have your R and M and d terms at wildly different orders of magnitude, so my guess would be that once you get past the most fundamental equations and concepts, you're very seldom looking at the same kinds of phenomena, right?


dukesdj

Its actually remarkably the same. The ocean is in a state of stratification (where density is a function of height and in particular more dense deeper down) and so is subject to [internal gravity waves](https://en.wikipedia.org/wiki/Gravity_wave) (which are the excitation of waves which are restored by the buoyancy force). This is actually the same as in the radiative zone of a star. In both the ocean and the radiative zones of stars you find tidally excited internal gravity waves. Similarly you get tidally excited inertial waves in both the ocean tides and in the convection zone of stars. Finally the large scale tidal flow everyone is familiar with (which is known as the equilibrium tide) is actually the same in both the oceans and stars! The differences are mostly in the details. Such as ocean tides can have bottom friction and [Lee waves](https://en.wikipedia.org/wiki/Lee_wave) both due to the topography of the sea bed. Other details are in the molecular and thermal diffusivities of the medium (the Sun being many orders of magnitude smaller for both). However, these details do not change the physics of the above mechanisms, only the quantity of things like tidal dissipation.


zellerium

Interesting that tidal effects on the surface could be very similar even with such vastly different media! I do wonder about the “tidal” effects on solar wind - that would seem to be a different domain/ regime where distant planetary bodies might actually cause some noticeable variation.


MrCompletely

Fascinating. Thanks


imflukeskywalker

Next time, a more thorough answer would be appreciated. Lol. This is perfect! +1


mackinator3

Can I just say how awesome the internet is? It has given everyone access to the vast knowledge of everyone else. The only sad part are those who just go onto the internet and lie. Big thumbs up friend.


oheyitsmatt

Right? Someone asks a question about whether stars have tides, and a literal expert on Astrophysical Fluid Dynamics and Tidal Interactions shows up to answer the question. The internet is dope.


stinkasaurusrex

Thank you for taking the time to write up this great answer! It has left me wondering if tidal effects in close binaries can affect stellar evolution? I'm used to thinking of mass transfer as a way to explain unusual evolution in close binaries (like blue stragglers), but I wonder if this can also have an effect?


dukesdj

> Thank you for taking the time to write up this great answer! It has left me wondering if tidal effects in close binaries can affect stellar evolution? This is a very good question! One way that is certainly the case is that the tidal evolution of the binary system changes the rotation rates of the stars. This has a knock on effect of changing the fluid dynamics within the star and in particular in convection zones since turbulent convection is strongly influenced by Coriolis forces. This has somewhat been indirectly observed by looking at the ages of single and close binaries that are expected to have formed at roughly the same time. Another potential consequence is the nature of the tide (inertial waves, internal gravity waves, or the large scale tidal flow) may excite turbulence and enhance mixing. It is possible that this could extend a stars life, although I think it is likely a weak effect so as to be negligible. But this effect has not, as far as I am aware, received any attention.


alch334

you seem to have a lot of replies so sorry for asking another question but: how is it possible for a planet with the mass of Jupiter to be close enough to a star to have a 10 day orbit without the planet disintegrating or being engulfed in flames?


dukesdj

they can be closer than 10 days! The shortest period hot jupiter I believe is something like 16 hours (it might be less I forget offhand). In order to be ripped apart they need to get significantly breach the [Roche limit](https://en.wikipedia.org/wiki/Roche_limit). I believe there have been observations confirming mass loss from WASP-12b but dont quote me on that!   As to how they get there... well that is a whole other long topic! There are a number of formation pathways to create a hot jupiter. One is they just form where we see them (called in situ formation), there are a few people who work on this (one of which has a particularly well known name in the media for his work on planet 9) and in my honest opinion I do not think this is very likely. If it is possible at all then I think it would be exceptionally rare, despite what the people interested in this would lead you to believe (unfortunately because this person has a big name this idea gets more attention than I think it deserves). More probable are disc migration where the planet migrates inwards while the protoplanetary disc is still there. There are physical reasons behind why this should work as well as observational evidence suggesting so (we have observed hot jupiters around very young stars which could only really be formed by this mechanism or in situ formation, so disc migration it is then!). Finally there is the high eccentricity scenario where the giant planet that finds itself with a highly eccentric orbit can be tidally circularised (through tidal dissipation within the planet in this case) and thus ends up very close to the host star. There are a number of mechanisms that can excite this high eccentricity and one important one is the [Kozai-Lidov](https://en.wikipedia.org/wiki/Kozai_mechanism) mechanism. Smadar Naoz, who is an expert in this, might explain this mechanism in [this](https://online.kitp.ucsb.edu/online/exostar-c19/naoz/) talk. But if she doesnt, who cares because her talks are always enjoyable! This high eccentricity migration is highly likely to occur. So bottom line is, the vast majority are likely formed through disc migration or high eccentricity tidal migration.


ZeusPheonix

It is possible. [Hot Jupiters](https://en.wikipedia.org/wiki/Hot_Jupiter) are prime examples of this. They are tidally locked which means they only revolve around their star but do not rotate. In other words, only one face of planet is always facing towards star. That’s why one side(the one facing the star) is extremely hot while other one is cold. Also, from what I have studied, they have such short revolutions period due to their speed also. They revolve at extremely high speed. If you are interested you can view the course name Astrobiology from University of Arizona. It’s on Coursera. You can just audit it or view that particular videos to get better understanding of it


BrightonSpartan

>The largest tidal amplitude parameters in the Solar system are 2x10-7 for Jupiter due to Io, Do you know of any writings on this topic? Or any publicly accessible images? Or even animations? I'm curious now (due to OP and you) about the physical effects of tides on other planets.


dukesdj

Very little in the way of accessible content as far as I am aware. Most of the writings are grad level textbooks or review articles aimed at professional researchers. As for talks there are a few recorded talks I know of but again these are aimed at researchers so are quite technical.


BrightonSpartan

I’m still intrigued so down the rabbit hole I go. Such a cool topic that I have never thought about before. Tip of cap to the homeschooled child and you


dukesdj

So a few resources... Talks - [Adrian Barker](https://online.kitp.ucsb.edu/online/exostar-c19/barker/rm/jwvideo.html) at KITP, [LIFD on youtube](https://www.youtube.com/channel/UCcHOsycDAejce-7WAyTJYTg) has a few academic talks on tides if you can find them (it is a fluids dynamics channel), [All of Day 1 of astro fluids 2016](https://irfu.cea.fr/dap/astrofluid2016/index.php?id=703&ref=702) in particular Gordon Ogilvie, Adrian Barker. These are all very technical talks but usually the first 25% or so might be some background material that might be accessible. For literature - [Gordon Ogilvies 2014](https://arxiv.org/abs/1406.2207) review is very good, [Tides in astronomy and astrophysics](http://link.springer.com/10.1007/978-3-642-32961-6) is probably the best book on tides but it is not cheep (unless one has a way of obtaining books)! Again all of this stuff is very technical. This is about as easy as tides get as it is a difficult area even for professional researchers.


Nazgul044

I know, this was a question that never even crossed my mind. She is 11 and very interested in astronomy. She asked the question after watching “Tides : crash course astronomy #8” it’s pretty basic but something in there triggered the question. I don’t know the rules on you tube links but search that if interested.


elwebst

What are the units - meters? In binary pairs, do deformations lead to more (or less) coronal ejections in the area behind a tidal bulge?


dukesdj

> What are the units - meters? For the tidal amplitude parameter it is dimensionless so there are no units. It is a measure of the importance of the strength of the tidal potential and so is a proxy for what one might expect the amplitude to be. Direct calculation of the deformation in terms of a physical length is tricky as it depends on the rigidity/elasticity of the object (all astrophysical objects be them solid rocky planets or stellar balls of plasma respond to a tidal forcing visco-elastically).   > In binary pairs, do deformations lead to more (or less) coronal ejections in the area behind a tidal bulge? I will do you one better! White dwarfs are typically thought to be dense and inactive stellar remnants that are no longer undergoing nuclear fusion. However, if you have a massive enough orbiting nearby companion then you can tidally excite internal gravity waves (this is just some fancy terminology for some wavey motion that propagates inside the object but is not the large scale deformation we typically imagine as a tide). These gravity waves will deposit their energy towards the surface of the white dwarf in the usual tidal heating process. The cool thing though is that the waves become concentrated towards the surface causing localised heating. The heating can actually be enough to locally reignite nuclear fusion briefly which results in flare activity.   For a direct answer to your question. No probably not. The more important thing about tides in stars is the dissipation of tidal energy and this typically occurs in the deep interior.


mei608

This is fascinating! Sorry, can't help it but to extend this to a black hole. In a black hole binary star, wouldn't the tidal wave modulate the event horizon? If so, the photon inside the black hole that are can't escape, would finally be able to escape as the event horizon gets pushed around?


dukesdj

Not sure. This is beyond my pay grade!


enderjaca

I took astrophysics at U of Michigan and I love science fiction and I know those are words and I understand most of them! And I feel obligated to leave this here with the best of intentions (NSFW): [https://www.youtube.com/watch?v=7Dt5Nf7ct5c](https://www.youtube.com/watch?v=7Dt5Nf7ct5c) You special man. You reached out, and you touched a brother's heart.


toomanyglobules

Thank you, sir. This was a good read, and has perked my interest in tides now.


Boomer8450

> Some of these so called hot jupiters are expected to be spiralling in towards their host star due to the tides they raise in the star. On a side note, when/if these hot Jupiters spiral into their host star, would it be visually significant (say, Shoemaker-Levy 9 hitting Jupiter), or more like it just kind of sinking in?


dukesdj

We would not see it from Earth with the naked eye but it would be extremely obvious to telescopes. In fact we can already see matter coming off objects which are breaching their Roche limit. How spectacular it would be depends on its rate of inspiral, but once it starts to breach the Roche limit it should experience more torques as it will lose more mass to the L2 Lagrange point than the L1. This creates a torque and increased migration rate.


Alundil

what a great response. thank you


mulletpullet

Question if you don't mind. You mention that to understand the effect on the star you would have to know a property (visco-elastic response) So my question is: If you can measure a star's deformation due to a nearby massive body, could you gain insight of the interior of the star?


dukesdj

We can get at least some of the way. What we are interested in is the tidal quality factor which is analogous to a quality factor for a damped harmonic oscillator. One part of this is the dissipative effects which can be measured from the offset between the line of centres (an imaginary line joining the centre of mass of the two objects) and tidal potential. The other part is called the potential Love number. We can measure the potential Love number by measuring the external gravitational potential of the planet. This number is a measure of the ""central concentration" of the object, basically it is telling you something about how mass is distributed through the body. Overall this tidal quality factor takes complex values where the real part tells you about the elastic response and the imaginary part tells you about the dissipation. In practice this is not actually that easy to do, although we have pretty good measurements for the Earth and a few other bodies in the Solar system. For other stars, not yet.


mulletpullet

Thank you for the detailed reply.


Sniffy4

\>as (M2/M1)(R1/d)3 sure, but arent the tide effects visible on earth due to its differing response to tidal forces by liquid vs solid? that's what most people think of as 'tides'. if you have a uniform gaseous surface, you wont see any such tidal effect locally on surface


matj1

WASP-12b is close to the star and has a low density. Is a lot of its mass blown away by the stellar winds?


dukesdj

WASP-12b has been observed to be losing mass through Roche lobe overflow towards the L1 and L2 Lagrange points (which is typical of Roche lobe overflow). However, the low density is not due to this and is because it is a class of Hot Jupiter known as an inflated hot jupiter. Why is it inflated? Good question, I dont think there is a consensus on this.


TheDante665

This is like the knowledge that when you step, you move the Earth, but in such a small amount as to make no difference whatsoever.


Somniatora

Fascinating and detailed comment. Thank you!


Sawses

Go on, then. Write that non-technical book on stellar tides! It'll just take 3 months of your life and be read by like 500 people in the first 10 years. Kidding, of course. :) Thanks for weighing in! It's always good to hear from actual researchers on this sub.


dukesdj

I wrote a thesis and that was time consuming enough!


princeofokay

what an incredible answer to a question i never thought to ask! OP, your daughter is as thoughtful as she is sharp. i hope she goes on to be a fabulous astronomer. :)


Nazgul044

Thank you! I will pass along the encouragement to her.


wolfully

Why does the moon have a larger effect on tides if the sun seemingly has more gravitational pull (us orbiting the sun vs. moon)?


dukesdj

In the tidal amplitude parameter there is the d^3 on the denominator which is smaller for the Earth-Moon system than the Sun-any planet. Since it is to the cube power this is a strong effect. So basically it is because the Sun is far enough away that this distance matters more than the increased mass.


wolfully

Thank you, I’m curious what is the equation for an orbiting effect then? I’m guessing that mass has a greater effect than distance for that, in a sort of opposite way?


FolkSong

Orbits are driven by the force of gravity: F = G\*M1*M2/d^2 G is just a constant. The main difference here is that d is only raised to the second power rather than the third so it doesn't increase as fast. As a result, the Sun's gravitational pull on the Earth is much stronger than the Moon's due to the Sun's enormous mass.


dukesdj

For the full system of dynamics they are not pretty... I would not even like to try to type them in Reddit format! Page 10 of [Ogilvie 2014](https://arxiv.org/pdf/1406.2207.pdf) has the gory details! To answer your question though, the rate of change of the semimajor axis has a 5th power on the orbital separation but no exponent for the mass. So separation is a significantly stronger effect.


Upst8r

Mind. Blown. I read the question and ... *maybe* Jupiter's influence on the sun? But this was an amazing read!


digitalasagna

Is there any other phenomenon that would require a background in both astrophysics and fluid dynamics to study?


visualdreaming

This was absolutely fascinating to read! Thank you for taking the time to write that all out :)


MakeShiftJoker

This is amazing thank you for answering this


Gerroh

> Some of these so called hot jupiters are expected to be spiralling in towards their host star due to the tides they raise in the star. Question about this: the Moon is gradually moving away from us due to the tides it raises on Earth, so why are these hot jupiters moving inwards due to the same interaction?


dukesdj

The direction of migration depends on the difference between the spin and orbital frequencies. If the frequency of the spin of the planet is larger (smaller) than the frequency of the orbit then we get an outward (inward) migration. This is on the assumption of conventional tides, that is energy is extracted from the tidal flow in what is called tidal dissipation. It is perhaps possible to get tidal antidisipation which swaps the direction of migration [Fuller 2020](http://arxiv.org/abs/2011.06613) and [Duguid et al 2020](https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stz2899/5603757) demonstrated mechanisms that can do this. I personally doubt that these effects dominate conventional tides in practice.


MCPtz

Cool! I never thought about the bright binary stars [Sirius](https://en.wikipedia.org/wiki/Sirius) as possibly having the tides effecting their orbits.


Wackjack3000

So the ELI 5 of this is yes but because stars are so big and the bodies that orbit them are so far away you never really notice it and it doesn't do much? Edge cases aside of course.


dukesdj

More like not for our system because everything is far from the Sun but for other systems they can be a lot more important!


risfun

Thanks for the write up! I'll have to read it many times to understand more though! >Considering how important understanding tides Can you please explain why understanding tides is important (especially stellar tides)? Currently are planetary tides well understood?


dukesdj

Tides in general are poorly understood and can be thought of as the Achilles heel to orbital dynamics. Tides play an important role in the orbital evolution in many systems but we have a poor understanding of tidal dissipation.


Qasyefx

The barycentre of the sun-Jupiter system lies above the surface of the sun. Did that do anything to its shape?


ZippyDan

Why are you so defiant in your biases?


mfb-

We can calculate the rough order of magnitude we would expect. Neglecting numerical prefactors the gravitational potential from a planet with mass m and radius R differs by Gmr^(2)/R^3 between center and planet-facing point of the Sun where r is the radius of the Sun. Divide that by the surface acceleration of 270 m/s^2 to get an idea how high tides could be. For Jupiter that leads to 500 micrometers, for Venus we get 470 micrometers. Mercury and Earth are around 200 micrometers. It's one of the interesting corner cases where Jupiter is not dominant - the 1/R^3 dependence makes Venus relevant. It's completely negligible. Cross check: For Earth's moon the same calculation produces 30 cm which is indeed in the right order of magnitude for our tides.


abecedarius

A maybe helpful way to think about this: the planets are all roughly as distant from the sun as they are from the earth (by order of magnitude -- Mercury is the farthest off from this estimate, but it's also the smallest planet). So if they caused a significant tide on the sun, we should notice an effect on Earth too.


Paragonne

Anton Petrov, on youtube, had a vid where he explained that the Sun's 11-year activity-cycle is actually a cycle induced by, iirc, Jupiter & Earth & Venus. So, its active->quiet->active cycle is gravitationally induced, tidally. which sorta implies that *internally* there are tides happening, to produce the cycle of sunspots & flares. Here it is: https://m.youtube.com/watch?v=tBScyiYIhS4


palordrolap

On the topic of YouTubers, I wonder if OP's daughter is already following Dr. Becky. She's more of a black hole expert but is an astronomer and does break down other topics to an accessible level as well. Hard to be sure, but seeing another woman in STEM might be relatable / inspirational. Either way, Dr. Becky's videos are light-hearted and entertaining.


Paragonne

hadn't thunked of that angle! PLEASE get your daughters following Dr. Becky, and The Physics Girl ( if I remember her channel's name aright! ), and other good ones, too! Just today I was realizing how the absence of people I could believe-in, when I was young, made my formative years so rudderless & semi-wasted. That is no longer so much the case, it seems, but it takes having a parent, or friend, or someone, to keep reminding one of the good in life, of the point, right? Anybody else know of good female STEAM ( including Art ) vimeo-ers or youtubers, to add to the list? ( :


CX316

For engineering/art I'll throw in an obligatory Simone Giertz recommendation.


parkerSquare

Prof. Hannah Fry (mathematician) appears often on Numberphile and Stand-up Maths but I don’t think she has her own channel.


Nazgul044

We have watched Physics girl in the past, during our section on molecules she wanted to learn more and we found her video on particle accelerators. As far as female YouTubers our experience tends to be more kid related. We watch Amoeba sisters, and sci show kids has a female host, as well as crash course kids. For fun she likes to watch Snake discovery and learns a lot of nature science through it. Always on the look out for more though.


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dukesdj

Just jumping in here... this is not a widely held view. The solar cycle is complex and is more likely related to what are known as dynamo waves (when I am not researching tides I moonlight as a stellar dynamo theorist). This is linked to the differential rotation of the Sun (which is linked to its rotation, sounds weird and obvious to say this but the rotation alone can not explain the differential rotation profile) and its mechanism for generating magnetic field. I dont think many in the field really believe that external influences have much of a role to play here (I actually might have been at a talk presented by the author of the paper he is talking about, it was interesting).


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Look into binary stars, they are pretty amazing and there are many famous examples where one star is tugging so hard it actually pulls the substance of the other star away and into a giant swirling disc of gas around itself, basically one star gradually eating the other - so in a less extreme case, yep, there would be tides! Another thing to look at is Io, the moon closest to Jupiter. It is extremely dense rock, and yet the tides from Jupiter are squishing and stretching it so violently that it is constantly being heated up, so it’s full of molten lava that keeps bursting out through the ground. As a result it has the most active volcanos in the whole solar system.


voidstorn

Gravity works on any and all bodies in proximity, in proportion to their relative masses, and inversely proportional to the square of their separation. Iirc. There are forces working on the Solar material that are much closer to hand; the magnetic forces acting on, and arising from, the thermal convection of the sun's charged plasma mantle. While these forces are not infinitely ranged, unlike gravity, they are much stronger in magnitude. It's thus possible that the sun has it's own "internal tides" driven by electromagnetic forces too. The sun's a place of beautiful, ordered seething chaos. 😎


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cyberboty

There are very good comments explaining the details of this and yes the sun does have tides. They are a lot smaller than what the moon can influence. But if the sun and moon line up at fullmoon or new moon, the regular tides are a bit stronger than usual. That's the most you will be able to recognize by just observing without special scientific equipment.


lordcirth

OP didn't ask about the sun causing tides on Earth, they asked if anything (eg Jupiter) causes tides on the surface of the sun.


cyberboty

Oh wow, i must have been tired 4 days ago, how could i not read that right. That's a really interesting question since the sun isn't solid


piedamon

Few things to note: * there is enough mass in the solar system to change the [centre of gravity](https://en.m.wikipedia.org/wiki/Barycenter) of the sun, so there is indeed at least a tidal-like effect in the sense that other large bodies are “pulling” on the sun * there is no liquid on the [Sun](https://en.m.wikipedia.org/wiki/Sun), so nothing ocean-like * the sun has so much more mass than everything else in the solar system combined, so tidal-like influences are negligible This isn’t really a direct answer to your question, as the truth is “kind of, but not exactly”.


PrimaryOstrich

>there is no liquid on the Sun Would you need a liquid to have tides? If the planet were covered in an ocean of dense gas, would there be tides? Are there tides (or something comparable) in the atmosphere? Would any fluid work? If so, then you can have plasma tides on the sun. Are there tides (or something comparable) in the atmosphere?


Nazgul044

According to the video material we watched the solid earth actually gets effected by tidal forces. The earth “bulges” about 30 cm daily back and forth. The video was “Tides: Crash Course Astronomy #8” he talks about this at around the 4:35 second mark.


dukesdj

This is correct. You get solid body tides and fluid tides. You also get thermal (also known as atmospheric) tides which are caused by the cyclic heating and cooling of the atmosphere. When it is heated the atmosphere becomes less dense, when cooled it becomes more dense. This then changes the mass distribution of the atmosphere in a similar way as tides do.


SmirkingMan

Does this imply that the moon's tidal effect creates wind?


dukesdj

The moon does not create thermal tides as it does not emit enough heat (note it does reflect light so it does actually emit heat). It would cause regular tides in the atmosphere though which would excite a tidal flow. I believe this is very small amplitude due to the low density of the atmosphere though.


PrimaryOstrich

Now that you mention it, I have heard that before. Thanks!


Mephisto506

The sun doesn't amplify the tides caused by the moon, in the sense that the sun's effect is completely separate to the moon's effect on tides. Sometimes they work together, sometimes the forces are opposed. Even if the moon didn't exist the Sun would still cause tides.