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Yes 12 ly is amazingly close! > If we presume there's nothing special about our little corner of the universe, then the distance to the nearest potentially hab
by joshuahedlund 7y ago
Yes 12 ly is amazingly close!
> If we presume there's nothing special about our little corner of the universe, then the distance to the nearest potentially habitable planets gives us an estimate of how many habitable planets are out there
I would put a slight caveat to this - I would argue we do know there's something "special" about our little corner of the galaxy, at least - we are in the continuously habitable zone - for example, there are billions of stars at higher densities closer to the core whose planets are likely uninhabitable due to toxic levels of radiation, GRBs, etc. So I actually might expect other planets near us to be more habitable on average than at least some other places in our galaxy.
But I also think it's too soon to know how potentially habitable these planets are, until we have a chance to check a bunch of other things on the checklist, like the long-term stability of the sun's output and the planet's orbits, the frequency of destructive solar flares, the frequency of asteroid bombardments (if there are no Jupiters to absorb them), etc.
Regardless the close distance should make it much easier to answer these sorts of questions than it would be far planets much farther away, and I'm excited to see what we can learn in the coming years.
- soulofmischief 7y agoWouldn't each system's star do a decent job of pushing back extra-solar radiation? Up to a point, obviously, but it would seem that planetary background radiation levels aren't a direct function of solar density.
- akiselev 7y agoIt'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 agoI'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 agoBelieve you are thinking of solar wind? That might counteract another source, but don't believe light radiation would be affected.
- soulofmischief 7y agoSolar 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 agoElectromagnetic 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 agoPhoton-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.
- erikpukinskis 7y agoNope! Some stars are in a stable orbit in a region with some NASTY orbiting interlopers who are eating star systems every million years and have just not made their way to them yet. We have made it at least a billion or so without getting too close to a nasty body so that says something about the region around us.
- samplatt 7y agoI'm guessing you've read Incandescence by Greg Egan? It explores the possibility that general relativity could be discovered by a pre-industrial civilisation living inside an asteroid in a very tight orbit of one those nasty interlopers.
- xelxebar 7y agoEgan is one of my all-time favorite SF authors. Was delighted and surprised to find his name popping up in some nitty-gritty, research-level algebra discussions recently. I haven't heard of Incadescence so it's definitely going on the list. Am also intrigued by Dichronauts too! Have you read it?
- cced 7y agoI often hear about the LY unit of distance. Why is it that we are still discovering things which are close to us in LY units? Wouldn’t we discover things at a distance of 5xLY before discovering things at a distance of 100xLY?
- Tuna-Fish 7y agoThings that are very luminous can be seen much further away than things that are very dim. This particular star is a tiny red dwarf, which is so dim we only just found the star itself in 2003. Our best planet-finding methods depend on finding signals in the light output of the host star. This is relatively insensitive to distance, but very sensitive to the properties of the star.