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It's not the density of the star but the density of stars. Dense clusters like those found in the center of our galaxy create a lot of secondary effects like bi

It's not the density of the star but the density of stars. Dense clusters like those found in the center of our galaxy create a lot of secondary effects like bigger stars pulling matter away from smaller stars (creating lots of background radiation and matter floating around) and then stars plow through those interstellar clouds, creating deadly bursts capable of cooking entire planets, stripping away their atmospheres, etc. In the center of the galaxy, these events happen so frequently that it's extremely unlikely life on any of the planets would survive long enough to evolve beyond simple single celled organisms.

soulofmischief 7y ago
I'm talking about the local solar density, not an individual star's density. Obviously that has little effect on the habitable zone of a planet. My question was about the ability of a system's star's own radiation to ward off extra-solar radiation and what kind of limitations we are aware of.
- mixmastamyk 7y ago
  Believe you are thinking of solar wind? That might counteract another source, but don't believe light radiation would be affected.
  - soulofmischief 7y ago
    Solar wind is a type of solar radiation. I thought perhaps a charged field of particles with an outward force could act at least partially as a shield in for some higher frequencies of electromagnetic waves.
- snowwrestler 7y ago
  Electromagnetic radiation from one star does not repel electromagnetic radiation from other stars. If it did, we wouldn’t be able to see stars at night from the Earth.
  - xelxebar 7y ago
    > If it did, we wouldn’t be able to see stars at night from the Earth. Ha! I love straighforward sanity checks like this. My initial reaction was to ask myself about photon-photon collisions which are im fact possible, but your comment gives a nice Fermi bound on how rare such events actually are. Cool!
    - Robotbeat 7y ago
      Photon-photon collisions are still technically possible... I remember a professor mentioning this as one question he got in grad school... draw out the Feynman diagram and you see a vanishingly small probability of photon-photon interaction. But yeah. Ionized particles like Galactic Cosmic Rays can be repelled by the local stellar magnetic field, but mostly the lower energy rays are deflected. Higher energy -to-charge-ratio GCRs can punch right through the weak stellar magnetic field, just like do for our Sun’s interplanetary magnetic field.
      - soulofmischief 7y ago
        Thank you for understanding my question before reaching for dismissal :) I knew low-energy waves are partially deflected, I just wasn't sure about high-energy waves. Makes sense!
  - soulofmischief 7y ago
    I should have been more clear in my question. Solar wind is a form of solar radiation, and I was curious about the effect of solar wind + the magnetic field that carries it would have on some frequencies of electromagnetic waves. I would expect mid-frequency radiation such as visible light to remain largely unaffected, I was thinking more about its effect on high-frequency extra-solar radiation. And it's likely not correct to visualize this as individual photons colliding but rather wave interference. Here is an article explaining the effect [0]. An excerpt: "The interplanetary magnetic field, which is embedded in the solar wind, deflects low-energy cosmic rays from us at the outer reaches of our solar system, decreasing the flux of these cosmic rays that reach us at Earth." [0] https://aasnova.org/2017/12/01/a-shifting-shield-provides-protection-against-cosmic-rays/ https://aasnova.org/2017/12/01/a-shifting-shield-provides-pr...
- zipwitch 7y ago
  It sounds like you're thinking of the heliosphere, which is the bubble in the interstellar medium created by the solar wind. The solar wind, in turn, is created by outflowing plasma from the Sun, and is also responsible for auroras and comet tails. The details of how far from the sun the heliosphere extends are complex, but it encompasses all the known planets. The heliosphere does provide us with a significant amount of protect from cosmic rays, which aren't actually electromagnetic radiation. Cosmic rays are extremely energetic particles, typically protons, coming in from outside the solar system. The Earth's atmosphere also does a good job stopping cosmic rays, which means their primarily a hazard to spacecraft, both manned an unmanned. (I don't know what effect cosmic rays would ultimately have on Earth if we didn't have the protection of both the heliosphere and our own atmosphere, but I know they have been investigated for links to mass extinctions.) They're a threat to space travel because they cause soft errors in electronics, and DNA and other radiation damage to human beings. The Sun's magnetic field - aka the interplanetary magnetic field or heliospheric magnetic field - travels with the solar wind and fills the solar system. It is magnetically coupled to solar system bodies like the Earth and Jupiter. As an amateur astronomer, the heliospheric magnetic field doesn't have any significant effects on photons coming into the solar system.
  - soulofmischief 7y ago
    That is incorrect. Energetic particles are radiation. Radiation isn't just photons. I don't think you understood my question very well because none of what you presented is new to me nor is it what I asked about. Still, thank you for the time and effort.

soulofmischief 7y ago

I'm talking about the local solar density, not an individual star's density. Obviously that has little effect on the habitable zone of a planet. My question was about the ability of a system's star's own radiation to ward off extra-solar radiation and what kind of limitations we are aware of.

mixmastamyk 7y ago
Believe you are thinking of solar wind? That might counteract another source, but don't believe light radiation would be affected.
- soulofmischief 7y ago
  Solar wind is a type of solar radiation. I thought perhaps a charged field of particles with an outward force could act at least partially as a shield in for some higher frequencies of electromagnetic waves.
snowwrestler 7y ago
Electromagnetic radiation from one star does not repel electromagnetic radiation from other stars. If it did, we wouldn’t be able to see stars at night from the Earth.
- xelxebar 7y ago
  > If it did, we wouldn’t be able to see stars at night from the Earth. Ha! I love straighforward sanity checks like this. My initial reaction was to ask myself about photon-photon collisions which are im fact possible, but your comment gives a nice Fermi bound on how rare such events actually are. Cool!
  - Robotbeat 7y ago
    Photon-photon collisions are still technically possible... I remember a professor mentioning this as one question he got in grad school... draw out the Feynman diagram and you see a vanishingly small probability of photon-photon interaction. But yeah. Ionized particles like Galactic Cosmic Rays can be repelled by the local stellar magnetic field, but mostly the lower energy rays are deflected. Higher energy -to-charge-ratio GCRs can punch right through the weak stellar magnetic field, just like do for our Sun’s interplanetary magnetic field.
    - soulofmischief 7y ago
      Thank you for understanding my question before reaching for dismissal :) I knew low-energy waves are partially deflected, I just wasn't sure about high-energy waves. Makes sense!
- soulofmischief 7y ago
  I should have been more clear in my question. Solar wind is a form of solar radiation, and I was curious about the effect of solar wind + the magnetic field that carries it would have on some frequencies of electromagnetic waves. I would expect mid-frequency radiation such as visible light to remain largely unaffected, I was thinking more about its effect on high-frequency extra-solar radiation. And it's likely not correct to visualize this as individual photons colliding but rather wave interference. Here is an article explaining the effect [0]. An excerpt: "The interplanetary magnetic field, which is embedded in the solar wind, deflects low-energy cosmic rays from us at the outer reaches of our solar system, decreasing the flux of these cosmic rays that reach us at Earth." [0] https://aasnova.org/2017/12/01/a-shifting-shield-provides-protection-against-cosmic-rays/ https://aasnova.org/2017/12/01/a-shifting-shield-provides-pr...
zipwitch 7y ago
It sounds like you're thinking of the heliosphere, which is the bubble in the interstellar medium created by the solar wind. The solar wind, in turn, is created by outflowing plasma from the Sun, and is also responsible for auroras and comet tails. The details of how far from the sun the heliosphere extends are complex, but it encompasses all the known planets. The heliosphere does provide us with a significant amount of protect from cosmic rays, which aren't actually electromagnetic radiation. Cosmic rays are extremely energetic particles, typically protons, coming in from outside the solar system. The Earth's atmosphere also does a good job stopping cosmic rays, which means their primarily a hazard to spacecraft, both manned an unmanned. (I don't know what effect cosmic rays would ultimately have on Earth if we didn't have the protection of both the heliosphere and our own atmosphere, but I know they have been investigated for links to mass extinctions.) They're a threat to space travel because they cause soft errors in electronics, and DNA and other radiation damage to human beings. The Sun's magnetic field - aka the interplanetary magnetic field or heliospheric magnetic field - travels with the solar wind and fills the solar system. It is magnetically coupled to solar system bodies like the Earth and Jupiter. As an amateur astronomer, the heliospheric magnetic field doesn't have any significant effects on photons coming into the solar system.
- soulofmischief 7y ago
  That is incorrect. Energetic particles are radiation. Radiation isn't just photons. I don't think you understood my question very well because none of what you presented is new to me nor is it what I asked about. Still, thank you for the time and effort.