Sunday, January 8, 2017

astro picture for the day/ Gliese 710 and generalisations / Mike Brown's Planet9 and planet definitions



Image Credit & Copyright: John Gleason


- a famous picture from 1833 of a 'meteor storm',






I remember reading somewhere(sorry, I didn't keep track of the reference; I managed to find the picture above from Leonid meteor shower wiki) that astronomers determined that the reason why there was  a meteor storm instead of your usual meteor shower(usually a trickle; one a minute just isn't that exciting) in  1833 is because a big cometary debris passed by . . . dangerously close.  To have that many meteors going on(millions per second) means large enough cometary debris was passing by . . . one so large, that if it had hit, we wouldn't be sitting here today.


Astronomers have likewise noted all kinds of things that will happen on astronomical timescales.  The sun will turn into a red giant  . . . four billion years from now.  This may seem like a long time from now, but astronomers have further noted that the sun will start getting to hot in a few hundred million years from now.  The process to becoming a red giant starts in a few hundred million years.

Another major astronomical event that should prove exciting is the Andromeda galaxy will collide with the Milky Way galaxy.  It will start to do so four billion years from now, also. Astronomers will tell you that both these galaxies are so diffuse, the chance of stellar collisions is slight.  This may be so, but the energies put into the motions of the stars is likely to disrupt planetary orbits. The gases and dust that hide the gamma rays and such from the center black holes is likely to be disrupted.  Anyways, I bring these things up because astronomers have determined that a star is heading towards our solar system in about 1.35 million years from now.


Gliese 710 is likely to get within 77 light days of our solar system.  There's likely to be a comet shower(up to 10 comets a year) for millions of years.  The chances are pretty good more than one comet hits the Earth in this time. In fact, Gliese 710's cometary shower is likely to be the biggest such comet shower our solar system has ever experienced.


Astronomers and Space expansion enthusiasts have been championing space colonization to overcome humanity getting wiped out from some astronomical(or nuclear winter) since the space age.  Some of this still sounds astronomically far off; but, it can't be too early to start.



- Mike Brown's demotion of Pluto from a planet . . . definition of a Planet . . . and Planet 9




I don't remember if I've posted this before; but, it can't hurt to repost.  Getting back to Mike Brown's discoveries and demotion of Pluto from planet-hood . . .



Mike Brown discovered Sedna and Eris amongst others. Mike then used these plethora of discoveries to push for demoting Pluto from planethood.  I'm of mixed feelings about it.  Of further note about Sedna and other such trans-Neptunion objects, Mike Brown and Konstantin Batygin have suggested some of these objects have odd orbits, suggesting the existence of a Neptunion like planet pretty far out in the Kuiper belt(not the Oort comet cloud even further out).



I recall people arguing against Pluto as a planet before Mike Brown.  But, there was little reason to till Mike Brown found so many close to pluto like sized objects even further out.  People noticed it was an iceball and an odd orbit for a long time. This is where I also argue the other way; yes, Pluto is different from the inner rocky planets and the gas giants; but, wait a minute!  The gas giants are different from smaller inner rocky worlds. So, to say Pluto is different in composition shouldn't demote it from planethood.



Mike Brown and Konstantin like to say that planets bully, or dominate, the gravity around them.  I just asked Mike Brown, "O.K. so what "planet" dominates the gravity of Charon - Pluto's moon?" 

I further pointed out the above about different compositions of the gas giants vs the inner rocky worlds. I then pointed out that Jupiter has a set of "planets" in orbit around  it much like the four inner rocky worlds and the four outer gas giants. I noted that the sun early on in its life, had stellar winds that pushed lighter elements further out in orbit around the solar system, leaving the heavier elements closer in.  The lighter elements formed the gas giants, and the heavier elemens the solar wind couldn't eject further out formed the inner rocky planets. Astronomers have shown that the Galilean satellites also display this difference in lighter and heavier elements.  The outer moons, Ganymede and Callisto, are made of more lighter elements than the inner "Planet" of Jupiter, Europa and Io. So, we could say that these round worlds(to distinguish from the comets and asteroids) are differentiated between inner and outer worlds, or planets. Likewise, we end up with icy round worlds even further out - Pluto, and now Sedna, Eris and more. So, we end up with three types of "Planets" - rocky, gas giant, and small icy worlds.


Scientists have known for a long time that the distinguishing feature of planets is that they have differentiation of elements(atom types).  They have an inner core that is made of heavier elements than the surrounding crust(or more layers).  This is an obvious definition of a planet from mere rocks(asteroids/comets and so on).



- I should have started this by pointing out that Planet is a vague word much like phlogiston was a pre- theory of fire before combustion was understood to explain fire.  Jacob Bronowski likes to point out phlogiston to explain his theory of knowledge.  I think this whole planet controversy is also an example of how people have a pre-vague concept, and then a later more mathematically well defined word.  See Jacob Bronowski's "Origins of Knowledge and Imagination."

10 comments:

  1. Studying the quantum vacuum: Traffic jam in empty space - https://phys.org/news/2017-01-quantum-vacuum-traffic-space.html

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  2. https://scienmag.com/magnetic-memories-of-a-metal-world/ planets are defined by having gone through element differentiation process.

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  3. Pluto is not an "iceball," as its composition is 70 percent rock. Thanks for your good points about distinguishing asteroids from small planets.

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    1. Thanks Laurel for pointing out Pluto's differentiated composition percentage.

      It's good to see someone listen to reason! I find the percentage of those who listen to this reasoning about Pluto pretty low. I get a like once in awhile on twitter(those accounts are now taken down for reasons I don't really know; i certainly don't agree with it).

      I know that Metzer and Alan Stern both gave a like; but, they don't want to say much more.

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  4. Mike Brown did state that he thinks that the IAU made a mistake developing a formal, scientific definition for "planet". He would've preferred to develop a "cultural" definition that states that Pluto is a planet "because we say it is" and that any new planets would need to be Pluto-sized or larger. He states this in this YouTube video (he starts talking about this at 1:09:59): https://www.youtube.com/watch?v=WHNO079G1i8&list=WL&index=121

    This video was recorded back in 2007 so I do not know if Brown still has this opinion; he might've just been sour at the time about Eris losing its planetary status.

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    1. Hello, thanks for sharing this video. I've watched a certain amount of Mike Brown and Konstantin Batygin's Planet9 talks; but, this is a new one, and maybe one if not the first one.

      I've watched the main talk, and now listening to the audience questions section while I write this. What I'm struck by in this talk is he mentions what separates asteroids from the planets, but this idea doesn't seem to hit him. That's kind of a main thought that I've stated here, and confronted him about it, with little to no response.

      Mike Brown also suggests the size of a planet. And, I pointed out, as I do here, that Gas giants are different from the inner rocky planets. So, I don't think the issue is size; Planethood is an invariant with respect to size. And what's that property? What distinguishes planets from the asteroids? And I'd say element differentiation; heavier elements go to the center of the round planet, leaving the lighter elements on top.

      And, he can't seem to reply.

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  5. I was able to figure out how to choose a name without providing a URL (I do not have a URL) just now; I was unable to figure this out at the time of my first comment, which is why I left my first comment as "Anonymous".

    Good point about how to distinguish a planet from an asteroid. I certainly want Pluto to be classified as a planet. Just because it's small and not a "gas giant" doesn't mean it's not a planet. So what if it doesn't "clear its orbit"? Even mighty Jupiter doesn't clear its own orbit with the trojans in its orbit. As you and others state, size isn't an issue. Mercury wouldn't clear other objects in its neighborhood either if it were in the Kuiper Belt; does that disqualify it as a planet? This just shows that the IAU's definition is flawed.

    I think the IAU went the direction of demoting Pluto (and Eris) from planethood to dwarf planets because those who opposed Pluto being classified as a planet spoke louder than those who supported Pluto being a planet; this was likely because there was no motivation to lobby for Pluto to be a planet since it was already classified as a planet at the time. Now that the IAU developed a scientific definition for a planet, astronomers who are lobbying to reclassify Pluto as a planet are developing their own counterdefinitions of a planet that, frankly, seem overreaching and desperate to me. For instance, Dr. Stern wants to classify several moons as "planets" so that there would be 100+ planets, which is ludicrous. Your definition is more reasonable and sensible to me.

    When I watched that YouTube video that I provided in my previous comment, I was pleasantly surprised that Dr. Brown preferred that "cultural" definition of keeping Pluto as a planet and that any future-discovered bodies would need to be at least the size of Pluto to be considered a planet. Prior to watching that video, I only heard him say that he supported the IAU's demotion of Pluto from a planet to a dwarf planet. Dr. Brown's proposal of that "cultural" definition would've been my preferred route and I wish I had thought of it before (I wish the IAU would've thought of it and adopted it too). I hope Dr. Stern and others propose it too, putting pressure on the IAU to adopt it. Unfortunately, it will be much more difficult to propose and adopt this cultural definition now that the IAU has adopted this current scientific definition for the last 14 years despite its flaws.

    The IAU and others who support the current scientific definition arrogantly says to those who oppose it (i.e. those who support Pluto being a planet) that if they don't agree with it, they don't need to accept it but it's not that simple. All textbooks and educational curriculum now adopt this scientific definition, stating that Pluto is a dwarf planet and that there are only 8 "planets". My 3-year-old son watches YouTube videos about planets, which all state this; I have to tell him myself that Pluto exists and that it is a planet, which I worry will just confuse him. I semi-jokingly tell him to tell his future teachers "You're wrong!" if they tell him that Pluto is not a planet.

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  6. I've posted as anonymous a few times, even when I wanted to use my childhood nickname. So, don't worry about that; i've had the same problems!

    Mercury could actually be considered a fragment. It was once a Earth/Venus, but it got pelted by a mars sized object, and now all we see is a little bit of a lighter element crust on top of the iron core. Mercury is an interesting case!

    If Mike Brown wanted a cultural planet, then he got one; he got pluto demoted for "cultural reasons."

    I've shared my ideas with Stern as well. I got a thumbs up, and then he want on with his definitions of a planet . . . .

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    1. There's a space probe going to an asteroid that is more iron than carbonaceous. I can only assume it's a fragment from a previous planet that is about the size of Ceres/Pluto. I keep meaning to the Astronomers in charge of that mission!

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  7. More proof(which I've known for awhile) is that the different types of meteors is due to a planet being destroyed, and making different types of asteroids/meteors

    Astronomers have known this for awhile, and yet they can't figure out the definition of a planet!

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