What Would a Nebula Look Like Close Up?

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Discussion Overview

The discussion explores how a nebula would realistically appear from a close distance, specifically within a fraction of an astronomical unit (AU). Participants examine the visual characteristics, particle density, and dynamic processes associated with nebulae, contrasting these with common portrayals in science fiction.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the realism of spaceships hiding in nebulae, suggesting that their appearance would differ significantly at close range compared to distant observations.
  • Another participant provides specific examples of nebulae sizes and distances, noting the vast scales involved and the expansion speeds of gases within them.
  • Particle density in nebulae is discussed, with one participant calculating an average density for the Ring Nebula and comparing it to solar wind densities.
  • Some participants note that the expansion speed of nebulae is much lower than that of solar wind, raising questions about the dynamics of these environments.
  • One participant asserts that nebulae would not significantly affect vision over AU scales, reinforcing the idea that sci-fi representations are unrealistic.

Areas of Agreement / Disagreement

Participants express differing views on the visual and physical characteristics of nebulae at close distances, with no consensus reached on how they would realistically appear. The discussion remains unresolved regarding the implications of particle density and movement within nebulae.

Contextual Notes

Limitations include varying definitions of particle density and the lack of consensus on the dynamics of nebulae. The discussion also highlights the complexity of visual perception in such environments.

dodo
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Merry christmas, and the stupid question of the day:
How would, reallistically, a nebula look like from a close distance, say, within a fraction of an AU?

I mention this because, in too many TV space shows, some spaceship hides into a nebula, as it would in a big cloud, which seems to me severely unrealistic.

First, we see nebulas from an enormous distance. I see no reason to believe they would look just like that at a close range, just as the blur in a foggy day looks denser the farther. For all we know, we could be in the middle of one. Or not? Is there an estimate of the density of ions within a nebula?

Second, there are violent processes associated with nebulas. Shouldn't we perceive them in movement, much as solar wind? Then again, the enourmity of the distances could cancel out the notion of movement, since, in order to be close to (some part of) something, you will probably be moving along with it. That is, if there is some "it" to be seen at a close range, in the first place.
 
Astronomy news on Phys.org
The Ring Nebula (M57) is about a light-year in diameter and is located some 2,000 light-years (3,500 ly according to UWashigton page) from Earth in the direction of the constellation Lyra.
http://faculty.randolphcollege.edu/tmichalik/PlanetaryNeb.htm
http://faculty.randolphcollege.edu/tmichalik/m57.htm

http://www.astro.washington.edu/labs/clearinghouse/labs/ProppnShort/proppn.html

Nebulae are Big, really BIG!

NGC 3132 is nearly half a light year in diameter, and at a distance of about 2000 light years is one of the nearer known planetary nebulae. The gases are expanding away from the central star at a speed of 9 miles per second.

http://www.atlasoftheuniverse.com/nebulae/ngc2237.html - According to this - NGC2237 125 ly for size!

Particle densities vary throughout a give nebula and among nebulae.
 
Thanks for your answer, Astronuc.

The links mention very little about particle density, thought a figure for mass density of the Ring nebula (for the entire nebula as an average, I guess) is given in the third link: 1.7 x 10^-10 kg/km3. which is, if I'm correct, 1.7 x 10^-25 kg/cm3; and given the mass of a proton as 1.67262158 x 10^-27 kg, this is around a hundred protons/cm3 in average, compared to (google-google) 7 protons/cm3 on our solar wind. Stormy weather!

However, the figure given for the expansion speed of the nebula, 20 km/s, is way lower than the 300-900 km/s of the solar wind. Please correct me where I'm wrong.
 
Yes the 20 km/s is quite low compared to solar wind velocities.

Solar Wind Data

http://pluto.space.swri.edu/image/glossary/solar_wind.html

http://www.agu.org/revgeophys/ogilvi00/ogilvi00.html

http://www.spacew.com/plots.php

http://www.dxlc.com/solar/solwind.html


Don't know if this will help, but it might have some useful numbers or references.

Material Enhancement In Protoplanetary Nebulae By Particle Drift
Through Evaporation Fronts
http://www.journals.uchicago.edu/doi/pdf/10.1086/423611


See - http://www.physics.hku.hk/~nature/CD/regular_e/lectures/chap13.html (bottom of page)
In most region of space, the particle density is about 1 atom per cubic centimeter, however, in some region of space, the density is over 1000 atom/cm3. (This is about the best vacuum made by human, while the density of air is about 1019 atom/cm3.) These regions are called nebulae. The typical size of a nebula is about hundred light years. Nebulae are made up of gases and dusts. An example is M42 in Orion.


Lecture 9 : HII regions and planetary nebulae
http://www.astro.utu.fi/~cflynn/astroII/l9.html

On the Reliability of Planetary Nebulae as Extragalactic Probes
http://www.aip.de/groups/sternphysik/stp/PDFFILES/2005/schoenberner_rc.pdf

I saw a number for IDP, but I'm not sure if it's relevant to nebulae.
 
Last edited by a moderator:
The nebula would not affect vision significantly over AU scales. Over light year scales, yes. The presentation of nebula in scifi is entirely unrealistic.
 

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