Imagine is our nearest neighboring star ejected a planetary nebula at the respectable speed of 1,500,000 km/hr. Much like the rotten egg nebula here: http://www.cnn.com/2001/TECH/space/08/24/hubble.nebula/index.html
Now imagine it had done this about 300 years ago so it was just about to arrive in our solar system?
What effect if any would the arrival of this nebula have upon the planets in our solar system? Pleasant night time lighting effects? Total obliteration? Something in between? What if we happened to be shielded by the sun at just the right moment…
How close would two stars have to be to each other for a planetary nebula from one to “devastate” the solar system in the other star?
The answer can be summed up with one word: zilch.
When the nebula is expelled by the star, it’s not very dense. After expanding for 300 years, it’s a high grade of vacuum. Furthermore, the solar system has a defense (as if it really needed one). The solar wind keeps most interstellar gas out of the solar system. The nebula would pile up at the bow shock where the interstellar gas meets the solar wind.
As far as visibility, it might be faintly visible to someone at a very dark site. For your average city dweller, they wouldn’t notice a thing.
Probably something akin to the 1910 pass of Halley’s Comet, when the Earth moved through the comet’s tail.
[ul]
[li]It would look cool.[/li][li]A lot of dumb rumours would circulate about health hazards and the Wrath of God and whatnot.[/li][li]Life would go on.[/li][/ul]
Actually, it wouldn’t even look cool. Those neat looking pictures of planetary nebulae depend on our distance from the nebula. If you were to get close to the nebula, the light of the nebula[sup]1[/sup] would be spread out over a large area of sky, making it extremely faint. Light polution in cities would easily wash it out. As I said, it might be faintly visible to someone at an extremely dark site.
[sup]1[/sup] Nebulae aren’t especially bright anyway. To get good pictures of nebulae, they generally have to take long exposures, the length of which depends on a number of factors such as the size of the telescope. For a color picture, they have to take several long exposures through different filters and then combine the results.
Oh come on, it would look a little cool…
Depending on the density of the nebula, (an extremely low but pretty variable amount) there could be high-atmospheric reactions, apparant meteor showers, an increase in star-twinkling, maybe some other stuff.
I’m not saying it’ll rival Terminator III but it might be worth driving out to a dark isolated spot with a good camera.
Until it happens, of course, the question is moot.
Actually, I believe the effect would be negligable. The density of a typical planetary nebulae is extremely low. By the time they get to be about a light year or so in size they get very faint.
If you were right up next to one you’d hardly see it, as has already been pointed out. You have to take the total luminosity and spread it out over half the sky. I have worked out these numbers a few months ago (for an upcoming Astronomy magazine article); you could be a light year from the Orion Nebula and not see the diffuse gas at all! You would see the filaments and the like, but not the background gas.
So you would see nothing. The typical planetary expansion loses steam rapidy too; they are rarely more than a couple of light years across. They snowplow into the gas and dust of interstellar space and lose momentum. So by the time of impact with our heliosphere (basically, the reach of the solar wind) it would have no momentum at all, and we’d probably never notice.
Caveat, as always: I haven’t worked out the numbers for the momentum, so I may be completely wrong. This is my (educated but not calculated) guess.