Welcome to planet Hempton. It’s just like Earth in every way except that when we look up in the night sky we see this stretching almost from horizon to horizon.
I have never left my beloved planet (nobody here is really all that industrious) but here you are, visiting from Earth. Howdy!
Are you able to feel any warmth from this big space-thing–like when you close your eye and face the sun on a clear day? Does it exert an appreciable gravitational force on Hempton? Sufficient to drive tides or even be detectable by human types?
Nebulas are not very dense. You wouldn’t feel any gravitational pull from them, otherwise the nebula would have condensed into a mass instead of a cloud. And if you were inside one, the pull would be in all directions throughout the sky, and would mostly cancel.
I assume that you would get a small amount of “greenhouse effect” from stars inside a nebula, but it’s probably not going to be much, as the gases and dust are very diffuse.
However, if you want to see what it’s like to be in a “nubula”, try internet gaming!
LONG before life (much less you) appeared on the planet it (and the star it orbits) would have cleared the immediate neighborhood (cosmically speaking) of any nebula gasses. A planet still forming with the nebula largely still there would be uninhabitable (likely still all volcanic and molten).
Any more distant gas that may drift in would not be noticeable to the inhabitants at all. The gravity would be negligible and at most maybe cause the solar system to drift an eensy bit if you were at the edge. Nothing you’d notice at all though.
I suppose the best you might expect is an interesting to look at night sky.
There are different forms of nebula. The one you linked to is a planetary nebula, created when a dying star expelled its outer shell in a violent explosion. That particular one happened something like 2200 years ago, and the nebula is about 2 light years from tip to tip - meaning that if you’re in that nebula, you were less than a light year away from the star. The little ‘fingers’ and other structures that you see in the nebula are the result of charged particles ripping through the gases as the star goes through conniption fits after the first ejection. Some of those particle eruptions are highly focused, and I don’t think you’re want your planet in the way.
Other types of Nebula are different. The Orion Nebula is a giant star forming region about 12 light years across. The Tarantula Nebula is huge - 500 light years across. It’s also extremely energetic, so much so that if it were as close to us as the Orion nebula it would throw shadows. The Orion Nebula is 1344 light years from us, so I don’t think you’d want to be anywhere inside the Tarantula nebula. It has a cluster of stars at its center with a total mass of about 450,000 suns.
On the other hand, many nebula are just dense clumps of floating gases that haven’t coalesced into stars. They’d be no big deal at all.
Nebula don’t produce heat. At best, they reflect it. So a nebula like the one in the picture is only as hot as the star (or star remnants) in the center. If you couldn’t feel the star, then you wouldn’t be able to feel the nebula either.
The mass in that kind of nebula is no more than there was in the star that exploded to form it, so a negligible force. Even larger star-forming nebulae would be pretty negligible in gravity from any distance where you could see them.
To put numbers to this, both gravity and the intensity of light/heat drops off according go the inverse square law (if you’re 2 times farther away, you have 1/4th the exposure). If we do the comparison based on the distance of the Earth to the sun (8.5 light minutes) for a nebula 1 light year away, we get 1/276 billion. Both in terms of tides and heat, when you start talking billionths it’s not something you can measure without fancy scientific instruments. The nebula would have to millions or billions of times times heavier/brighter/hotter than the sun to be felt.
Direct gravitational forces fall off as the inverse square, but tidal forces fall off as the inverse cube, which makes them even more negligible at a distance.
I wasn’t thinking of gravitational forces - I was thinking about the highly energetic stuff thrown out of the star, often into fairly tightly focused beams of charged particles. I’m not sure how close you’d have to be before it did bad things to your planet. Of course, if your planet is in there, you’ve already had your sun turn into a red giant, so there’s probably not much life going on anyway. Any planet that was in the habitable zone of the star when it was stable would be fried when the thing turned into a red giant. It would also be a lot closer than one light year.
A supernova 100 light years from here could do serious damage to the Earth’s atmosphere and kill unprotected astronauts. A supernova a handful of lightyears away could kill us. So I don’t think I would want to be inside that nebula.
