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."

1 comment:

  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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