From this question in World Building, it is speculated that planets in nebulas are not greatly affected by the presence of the nebula. This being the case, how do we know that the earth itself is not in a nebula? Has this been tested?


This depends a lot on exactly how you define a nebulae, but we are actually in a very dense region of the interstellar medium, the local interstellar cloud.

local cloud

Observing it directly from Earth is very difficult, due to sunlight and the solar wind, but its magnetic field has been measured by the Voyager 2 probe.

Assuming it is mostly hydrogen and helium, there are only about 1-2 ng/km³, so it is not a lot to observe. The actual properties of the cloud are still very uncertain.

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  • $\begingroup$ How should such 2D maps of space be interpreted? As if they were seen from a certain place, like a photo, ignoring the depth? Or are they drawn with correct relative distances but wrong angles between objects? $\endgroup$ – LocalFluff Feb 19 '16 at 9:06
  • $\begingroup$ @LocalFluff checking the galactic coordinates of the stars in the map seems to indicate that it is a view from galactic north. I think there simply is not enough information available to make a more accurate map. It is more like "probably a denser part of a cloud stretching several light years towards the galactic centre and anti-spinnwards."" $\endgroup$ – SE - stop firing the good guys Feb 19 '16 at 9:14
  • $\begingroup$ This has all been new and interesting to me. After reading that Wikipedia article, I intend to tell everyone I know that we live in the "Local Bubble". $\endgroup$ – Robert Feb 19 '16 at 19:55
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    $\begingroup$ This is informative, but I'd be interested in an elaboration upon "depends a lot on exactly how you define a nebulae". So we're in a nebula using some definitions of nebulae? $\endgroup$ – DCShannon Feb 25 '16 at 3:53

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