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Can we seek out worlds closer to the center of the galaxy?

  1. Mar 16, 2012 #1
    From what i know there is this Goldilock Zone of the galaxy where is not too much radiation coming from the Super Massive Black Hole at the center of our galaxy and where our solar system is...
    but in the future, can we venture closer to the center of the galaxy where is no more the galactic goldilock zone to find potential habitable worlds?:confused:
     
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  3. Mar 16, 2012 #2
    Recently we've been finding planets orbiting metal poor stars (measured as the Fe/H ratio), which we've only recently started looking at, so it's debatable as to whether the Galactic Habitable Zone is actually a useful concept when considering whether the star has enough heavy elements to produce terrestrial planets.
    See the graph here
     
  4. Mar 16, 2012 #3
    But if a star is poor in metals, isn't more probable for it to produce Gas giants and ocean worlds rather than solid?
    And anyway, if a terrestrial world is produced closer to the galactic core, can there even start evolving life?
    Is nature that tricky?
    i mean there are heavy bombardments of radiation...:uhh:
     
  5. Mar 16, 2012 #4
    Does anyone have any details on that alleged radiation problem? I don't find it very convincing.

    Is it due to supernovae happening very often? If that happens, then one of them may go off close enough to a planet to give it a big dose of ionizing radiation.
     
  6. Mar 16, 2012 #5

    Drakkith

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    The radiation isn't from the SMBH, but from the denser collection of stars near the core. And I'm not sure such areas are "heavily" bombarded with radiation. Consider that even a star that outputs 1 thousand times as much radiation as the Sun would need to be within 1 thousand AU to equal the amount of radiation falling on Earth that the Sun already does. 1 thousand AU is only 1.6% of 1 light year. Even considering that a massive star puts out more UV and other high frequency light than visible light, that still puts a star as needing to be exceedingly close (within a light year) to really pump up the amount of radiation in the solar system.

    But, as I am not a professional astronomer, take my opinion with a grain of salt, as I could easily be wrong.
     
  7. Mar 16, 2012 #6

    marcus

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    I'm also not a professional astronomer, just a retired mathematician who loves the stuff and watches from the sidelines.
    I agree with Drakkith about the radiation not being such a great obstacle. Our sun makes a bunch of ionizing radiation (a danger to astronauts) but our atmosphere shields us from it pretty well.

    AFAIK our galaxy's central BH is not really a big deal. It is not like a quasar with those huge lethal beams jetting out along the North and South pole axis. It is only 2 or 3 million solar masses, as I recall. Anybody who knows different, please correct me! AFAIK it is a comparatively harmless BH. It might be fun to live closer in towards the galaxy's central bulge. I think.

    Does anybody have an online source where one can read up on what determines the socalled "habitable zone" of a galaxy?
     
  8. Mar 16, 2012 #7

    Drakkith

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  9. Mar 16, 2012 #8
    That's a reasonable assessment for hot-star ultraviolet light -- you have to be very close to receive much of an effect.

    Milky Way - Wikipedia
    Stellar Populations

    Density of stars near the Sun: 0.122 per cubic parsec (all), 0.0147 pc^(-3) (brighter than mag 8.5).

    In the center of our Galaxy: "hundreds of thousands". That means that the average separation of stars there is about 0.005 times the average separation out here. Moving a star that much closer means adding -11.5 to its apparent magnitude, and the brightest stars would be as bright as the full Moon. It's hard for me to estimate how many stars would be visible, however. If one extrapolates from what stars are visible from the Earth, one gets well over a billion stars, but that would mean a lot more than that in the few hundred parsecs around our Galaxy's center.
     
    Last edited: Mar 16, 2012
  10. Mar 16, 2012 #9
    Finding the Galactic Habitable Zone | astrobites mentions [1107.1286] A Model of Habitability Within the Milky Way Galaxy, which estimates a Type II supernova as having a sterilization distance of about 8 parsecs and a Type Ia one of having a sterilization distance of 20 parsecs.

    The sterilization happens from destruction of ozone, which lets more of the planet's star's UV in. It's unlikely to be complete sterilization, however -- there are lots of organisms that live in UV-proof habitats, or may otherwise be able to survive it.

    Gamma rays may have devastated life on Earth - 24 September 2003 - New Scientist -- speculation about the end-of-Ordovician mass extinction being due to a gamma-ray burst that does something similar to the Earth's atmosphere.

    Type II supernovae will happen wherever there are recently-formed stars, because some of them will be massive to become a Type II supernova. There are about 2*10^(-3) Type II supernovae per year in our Galaxy, the mass density near the Sun is 0.05 solar masses / pc^3, and the mass of the Galactic disk is about 2*10^10 solar masses (The mass distribution in the galactic disc. I - A technique to determine the integral surface mass density of the disc near the sun. | Mendeley; radius of 12 kpc assumed). So the volume of the Galactic disk is about 10^9 cubic parsecs, meaning a Type II supernova rate of 2*10^(-12) per pc^3 per year.

    That means about 20 Type-II supernovae less than 8 pc from the Earth over its history, or 2 since the base of the Cambrian. Which may be about right for the end of the Ordovician.

    Older stars have a probability of about 1% of becoming a Type Ia supernova; they have to become white dwarfs in close binaries. The rate of Type Ia supernovae in our Galaxy is about 4*10^(-3) per year. Using a Galactic core radius of about 1 kpc, and assuming that most Type Ia's are there, I find a rate of 1*10^(-12) per pc^3 per year. If the Solar System was in the core, it would be exposed to 150 supernovae over its history, and near the center, it would be even worse.
     
  11. Mar 17, 2012 #10

    Chronos

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    Stellar population demographics do not support the idea earth has been bombarded by a couple dozen type II supernova within 8 parsecs over its history.
     
  12. Mar 17, 2012 #11
    I'm not sure about one thing...
    Does stars usually orbit spiral inwards to the center of the galaxy or they just stick calmly in their relatively circular orbits around it...
    OR they orbit spiral outwards, farther away, from the center of the galaxy and if they are closer in to it then they start orbiting spiral inwards?
     
  13. Mar 17, 2012 #12

    Drakkith

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    It depends on the eccentricity of the orbit. Our sun has a fairly circular one and doesn't drift much either way. Interactions with other stars and stellar objects can cause orbits to change over time though.
     
  14. Mar 17, 2012 #13
    But the stars of our galaxy do get abbandoned in the intergalactic space if they are on the edge of the galactic disk?:confused:
    And if a star starts orbiting spiral inwards what happens when it reaches the SMBH at the center?...But it can even reach the core of the galaxy in it's lifetime?

    And another question:
    Are there wild solar systems floating in the intergalactic space... i mean literaly wild and alone??
    Cause i've made a few small calculations about this subject and i'm just not sure... My cosmology teacher says it is probable and my physics teacher says it can't be and i'm just extremly confuse!!!:confused::confused::confused::confused:
     
    Last edited: Mar 17, 2012
  15. Mar 17, 2012 #14

    Drakkith

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    Not unless it interacts with another star or something and gets thrown out.

    Sure, if it get perturbed out of it's normal orbit. However this is fairly rare compared to the number of stars in the galaxy. If it reaches the SMBH in the center of the galaxy, it will be torn apart like anything else would.

    There are extragalactic stars that have been thrown out, so I think it's a safe bet that there's a star out there outside the galaxy with some planets around it.

    I can't see there NOT being at least a few star systems out in intergalactic space. And I would believe your cosmology teacher over your physics teacher when it comes to astronomy.
     
  16. Mar 17, 2012 #15
    Why do you say that? Do you have numbers that are better than mine?
     
  17. Mar 17, 2012 #16

    Chronos

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    I dont recall seeing any demographic numbers you posted. You cant apply numbers derived from galactic core counts to our neighborhood.
     
  18. Mar 17, 2012 #17
    I just made a call to my Cosmology teacher and ask him to help me in a small calculation about the possibility of stars forming out of intergalactic nebullae...
    First i don't know if they have a source that will cause it to start evolving into a protostar
    but i theorized...
    Another issue is that i'm to lazy to make another calculation of how that intergalactic nebullae appeared in that intergalactic space...
    is it:
    1-Material left over from the primordial material of the Big Bang...
    2-Material that flew away from it's galaxy
    3-(WARNING SPECULATION) PROBABLE some wild SMBH left over from violent galactic collision just magnetically influenced a cluster of free floating atoms and molecules to coalesce into clouds of Hydrogen and Helium and... eh...:uhh:
    well maybe that's the influence necesarry to make that cloud coalesce into a protostar...?:biggrin: isn't it?????:confused:
     
  19. Mar 17, 2012 #18
    ok but from what i know solar systems closer to the center are new solar systems, it tuke billions of years for earth to turn habitable, so i would assume that in the center the planets are still new and so maybe less likely to be habitable
     
  20. Mar 17, 2012 #19

    Drakkith

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    Are we talking one to a few dozen stars? Or something like a small dwarf galaxy of thousands - millions?
     
  21. Mar 17, 2012 #20
    No.
    About how do wild solar systems form through intergalactic space out of intergalactic gas and dust.
    only this is my theory of how do wild solar systems (and how those wild gas and dust clouds appear[read that "issue" that i had and those 1-,2-,3- subjects]) form besides being thrown out of their galaxy...
    And a link of how new galaxies could form in modern times... (starting from few dozen stars all the way into forming a central SMBH and a good looking spiral disk :biggrin:)
     
    Last edited: Mar 17, 2012
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