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Planets evenly spaced on log scale
- debt 9y agoWas kind of hoping to see pictures of the planets themselves, evenly spaced on a log scale. Those line graphs were a little less exciting.
- rcthompson 9y agoUnfortunately, I believe we only have decent photos for one of the mentioned solar systems.
- EGreg 9y agoWould have made for a great illustration, methinks!
- pacaro 9y agoI’m working on a solar system chart for my daughter, to my eye it’s more aesthetically pleasing to scale both distance from the sun and radius by square root. Regardless of your approach the sun is too big to usefully represent on the same scale and have all other objects be visible
- bdamm 9y agoGraphs of exoplanet orbits exist and are easy to locate: For example: http://www.openexoplanetcatalogue.com/planet/KOI-1843.03/ http://www.openexoplanetcatalogue.com/planet/KOI-1843.03/ It isn't on a log scale but this example is easy to see as a counterexample to the OP as there are two planets out in large orbits that orbit close together with a large gap between the first planet.
- topspin 9y agoResolving extrasolar planets so difficult that one can concisely list[1] all of the planets that have ever been resolved and adding an entry is a significant achievement. Directly imaging extrasolar planets is only possible given certain conditions (type of star, orbit, planet size/type, etc.) The vast bulk of extrasolar planets cannot be resolved directly with contemporary instruments. [1] https://en.wikipedia.org/wiki/List_of_directly_imaged_exoplanets https://en.wikipedia.org/wiki/List_of_directly_imaged_exopla...
- outworlder 9y agoWe cannot even take a picture of Pluto that's bigger than a few pixels without sending a probe there. Not sure images from extrasolar systems, even if available, would be very exciting.
- bdamm 9y agoIt's an interesting conjecture, but what about the anomalies? There are over a hundred planet systems discovered by Kepler with various levels of confirmation. None of them are mentioned here. The essay only lists 9 systems. How do the rest compare? Are there anomalies in unconfirmed systems? Why were these systems chosen; was it a random selection?
- rcthompson 9y agoThe post explains exactly why these systems were chosen: because they have the most planets. This is every known system with 6 or more planets (according to the OP).
- olympus 9y agoYou need a system with more than two planets. A system with only two planets is going to be linearly spaced on any type of scale. Once you've filtered out systems with two or fewer planets, you need orbital measurements with decent precision to tell whether a plot of planet spacing is actually linear on a log scale or not. Measuring a planet's orbit requires a decent amount of observation (since we can't measure star/planet mass directly and don't usually measure period directly), so unconfirmed systems likely don't have good measurements. It's likely that most of the unmentioned systems get filtered out by one of the above two criteria.
- grkvlt 9y agoAlso, even if we detect a system with N > 3 exo-planets, we often cannot tell if there are more than N, but below the threshold of detectability, making the plots incomplete and incorrect.
- kpwagner 9y agoFascinating that this relationship scales from solar systems in which the planets are close to the star to solar systems that are more spread out. I wonder if the mass of the star has an effect on the average distance that the mass of the rest of the solar system is from the star. I also wonder if the mass of the star has a correlation with the tightness of the logarithmic distance relationship exhibited in this article.
- delecti 9y agoBased on the graph for our system, it seems more likely that the mass of the planets affects the correlation than the mass of the star. Mars is a bit small (relative to earth) and is a slight dip from a straight line, whereas Jupiter which is quite large is a jump up above the straight line. If hypothetically the planets beyond Jupiter were all small and rocky then it seems they'd dip back down past the straight line again.
- hinkley 9y agoI suspect some expert will come in and tell us that there is some fundamental of orbital mechanics which correlated to the observations. That is, stable planetary systems have orbits that correlate with the area of the orbit (the square of the distance from the star) I recall one of the earliest breakthroughs in orbital mechanics was someone figuring out how the area of a slice of a elliptical orbit was the same anywhere in the orbit, when the angle of the arc is calculated as a unit of time and not degrees. Not to say you’re wrong. I think you’re right, but the quality you’re attributing to the system is a behavior of the system that has an underlying link to physics that may already be well explored. Just nobody has bothered to put a pretty plot in front of us armchair types and students before.
- vkou 9y ago> I recall one of the earliest breakthroughs in orbital mechanics was someone figuring out how the area of a slice of a elliptical orbit was the same anywhere in the orbit, when the angle of the arc is calculated as a unit of time and not degrees. That would be Kepler's second law. It states that a line between the sun and the planet sweeps equal areas in equal periods of time.
- rcthompson 9y agoThere's an extra large jump from Mars to Jupiter, but that's because there's an asteroid belt between them, which might be an aborted planet. If you put the average distance of the asteroid belt as planet number 5, I bet it would look even more linear.
- olympus 9y ago??? Adding a point in between two other points literally can't make something more linear, it can only make it less linear.
- rcthompson 9y agoI mean that the asteroid belt would be counted as a 5th planet, and Jupiter would be 6, and so on.
- olympus 9y agoAh, I understand now. Increasing the index of the outer planets is what would make the fit better, and the asteroid belt is a good way to justify it (and happens to be consistent with some other theories about the solar system).
- afthonos 9y agoThe x-axis is the planet (+aborted planet) count. You’d be shifting all later planets over by one.
- deleted 9y ago[deleted]
- blacksmith_tb 9y agoSome models[1] suggest that Neptune and Uranus formed closer to the sun, and then migrated to their current orbits later (explanations vary between Jupiter and Saturn pulling them out, or some extrasolar mass). 1: https://en.wikipedia.org/wiki/Neptune#Formation_and_migration https://en.wikipedia.org/wiki/Neptune#Formation_and_migratio...
- perlgeek 9y agoOne has to be careful with inspecting log graphs by mere looks. What looks like a small difference from expected to actual value in log scale can be very large difference in terms of actual values. So it bothers me a bit that there is no actual fit and error margins.
- liberte82 9y agoWhat looks like a small deviation is only actually a large difference on a linear scale, in these graphs. On a logarithmic scale, it’s a small difference. That’s the point of scaling it logarithmically in the first place, to show how closely the planets line up on this scale.
- perlgeek 9y agoThe purpose of plotting it on a logarithmic scale is to demonstrate a power law, not necessarily to obscure a deviation from the linear-in-log power law.
- floil 9y agoMoreover, x and y are not independent on this plot -- x is just the rank of y. A graph constructed this way can never dip down. So a linear-looking upward trend is basically guaranteed.
- petters 9y agoCompletely agree. I made a plot with a uniform distribution: https://www.strandmark.net/Planets.html https://www.strandmark.net/Planets.html So I am not sure there is anything going on here.
- deleted 9y ago[deleted]
- wpietri 9y agoMar's Law: "Everything is linear if plotted on a log-log scale with a fat magic marker." It's #6 on the excellent (and surprisingly software-applicable) "Akin's Laws of Spacecraft Design": http://spacecraft.ssl.umd.edu/akins_laws.html http://spacecraft.ssl.umd.edu/akins_laws.html
- amelius 9y agoSomething tells me that the mass of the planets should be in the conjecture somewhere, because small objects have little meaning and perhaps would not even classify as planets.
- mikekij 9y ago...sort of like what you’d expect inside a simulation.
- Retra 9y agoA simulation is very general concept. You may as well have said "sort of like what you'd expect to hear with your ears." Obviously you hear things with your ears. And equally obviously, you can expect things in a simulation.
- rdiddly 9y agoAnyone care to speculate based on physics why this might have worked out this way?
- yonkshi 9y agoIndulge my wild guess (I'm not a physicist): If the proto solar system's matter distribution was a Gaussian-like distribution, it would make sense that matter density droped in a logarithmic scale, and thus planets formed droped logarithmically w.r.t radius. More intuitively.. further away from the sun has less probability for rocks/particles to interact with each other.
- Someone 9y agoIn our solar system, the small planets are closest to the sun. Jupiter, with 72% of all planetary mass, is more than twice as heavy as all other planets, combined. Saturn, Uranus and Neptune take most of the remaining 28% (https://en.wikipedia.org/wiki/List_of_Solar_System_objects_by_size#Graphical_overview https://en.wikipedia.org/wiki/List_of_Solar_System_objects_b...) (Of course, there also is way more volume that far away)
- clord 9y agoAnother wild guess: a sphere of gas collapsed to a rotating disk. If you take a sphere and squash it flat, the middle has most of the mass, and it declines to zero as you get farther. I would guess the pattern of falloff of a squashed sphere is roughly logarithmic. That pattern gets quantized into planets, and so we see the original spherical distribution in our planets.
- jacquesm 9y agoThat makes a lot of sense.
- alan 9y agoWe might be able to start using this as a way to specify planets, rather than the arbitrary number-by-discovery. Try StarName(with catalog info)#log(approximate radius of orbit) Earth would we Sol#0 Kepler-90#-1.3, Kepler-90#-1.1, out to Kepler-90#0 for the outermost one on his graph. That way, finding a new planet doesn't require either renumbering to specify where the planet is relative to the star. (BTW, I'm not real happy about using AU as the base measurement. It might be better to use Megameters since you're less likely to end up with negative log)
- saagarjha 9y agoWhat would you do for highly elliptical orbits?
- jwiley 9y agoSome more discussion on Reddit: https://www.reddit.com/r/askscience/comments/58plow/why_are_the_planets_logarithmically_spaced/ https://www.reddit.com/r/askscience/comments/58plow/why_are_...
- wl 9y agoMar's law: Everything is linear when plotted on a log-log scale with a fat marker. (I know this is a lin-log plot)
- antognini 9y agoAs a former dynamicist, the underlying reason for this correlation is that planetary systems with many planets are always on the edge of dynamical instability. In other words, these kinds of planetary systems with lots of planets are always packed with as many planets as they can support over any given lifetime. It then turns out that the stability criteria imply that the system cannot be any more packed than having approximately log-equal spacing. In fact, if you take a star and put planets around it with a log uniform distribution and evolve it for a while, you find that eventually the planets that remain roughly fit the Bode-Titus law [1]. (I don't think the reasons for this are entirely well understood.) One consequence of this is that our own solar system has been around for about 5 billion years, and is therefore probably unstable on timescales of 5-50 billion years. Indeed, long-term simulations indicate that there is a few percent chance that Mercury will get kicked out of the solar system or crash into Venus or the Sun before the Sun dies in ~5 billion years [2] [3]. [1]: https://arxiv.org/abs/astro-ph/9710116 https://arxiv.org/abs/astro-ph/9710116 [2]: http://www.scholarpedia.org/article/Stability_of_the_solar_system#Marginal_stability_of_the_Solar_System http://www.scholarpedia.org/article/Stability_of_the_solar_s.... [3]: http://adsabs.harvard.edu/abs/2009Natur.459..817L http://adsabs.harvard.edu/abs/2009Natur.459..817L
- yummybear 9y agoI wonder what effects Mercury crashing into the sun would have - large solar flares? Nothing at all?
- dbasedweeb 9y agoNothing much. The Sun is most of the mass in the Solar system, by over 97%. Most of the rest of that mass is Jupiter, followed at quite a distance by Saturn. Jupiter has more than 5700 times the mass of Mercury. In other words, next to the Sun, Mercury is a teeny little speck that would barely even leave a “splash” as it roasted to a cinder in its corona. It would be the most underwhelming event you can imagine, for Sol. For Mercury it would be an exciting journey of vaporizing outer layers, being torn to little shreds, and those shreds vaporizing completely (all before it contacted anything like a “surface”).
- rhelzerm 9y agoAnything is evenly spaded on a log scale...