In Reality, Nebulae Offer No Place for Spaceships to Hide

Article written: 22 Feb , 2013
Updated: 23 Dec , 2015

In the Battlestar: Galactica universe, nebulas are a nifty spot to hide from the Cylons that are plotting to kill humanity. There’s just one problem with the hypothesis, though — these diffuse areas of gas in our universe are actually very faint, even if you get close up. Probably too faint for a hiding spot.

Prequel Battlestar Galactica: Blood and Chrome (released on DVD this week) shows the young William Adama flying around the universe with pretty nebulas in the background. That’s not anywhere near the truth, Harvard astronomer Peter Williams told Universe Today.

In an e-mail, Williams explained that bright nebulas are a common misperception seen in Star Wars, Star Trek and a host of other sci-fi series.

The big issue is that nebulae are just too faint for the human eye to see. And while it’s tempting to think that they’d look brighter from up close, in fact this isn’t actually true — they actually look just as bright from any distance! This is a law of optics, known in the jargon as the “conservation of surface brightness”. The key is that there are two competing effects in play. Imagine that you can see a nebula that’s, say, the size of the full moon.

Yes, if you get closer, your eye will receive more total power from the nebula. But the nebula will also look bigger, so that energy will be spread out over a larger visual area (technically: “solid angle”). The physics tells you that the power per solid angle in fact stays exactly the same, and this quantity is precisely the “brightness” of an object. So if nebula are too faint for to see from Earth with the naked eye — and they are — getting up close and personal doesn’t help any.

Those bright colors surrounding Battlestar's ships are not actually what you would see if nestled in a nebula, according to  Harvard astronomer. Credit: Battlestar Galactica/SciFi (screencap)

The opening sequence in Battlestar: Galactica shows the ships hiding in a bright nebula. Credit: Battlestar Galactica/SciFi (screencap)

Further, Williams, explains, the bright colors we’re used to seeing in Hubble Space Telescope images are just an approximation of what a nebula actually looks like.

Reproduced images of nebulae don’t portray their colors accurately. As you may know, some astronomical images use “false color” to represent wavelengths of light that humans can’t even see. This does happen with images of nebulae, but nebulae really are colorful, and many nebula images try to reproduce those colors faithfully. No current reproduction, however, can be truly accurate.

The Crab Nebula. Image credit: Hubble

The Crab Nebula. Image credit: NASA/Hubble Space Telescope.

The problem is that the colorful nebular emission comes from reactions that produce light at a few, specific wavelengths; meanwhile, our inks and pixels emit over much broader wavelength ranges. We can mix these broad ranges in ways that approximate the narrow ones, but the results aren’t quite the same.

For an entertaining look at the science of nebulas, Williams recommends this entertaining video by astronomer Phil Plait, a long-time friend of Universe Today who is best known for his Bad Astronomy blog (now at Slate). “If you were inside [the nebula and looked down], you wouldn’t see it,” Plait says in this 2008 clip.

Guess it’s time to find another spot to hide.

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20 Responses

  1. Hans Cummings says

    So, if we were currently in a nebula, would we have any way of detecting that?

    Also, is there any distance at which an observer could park their hypothetical starship to get a fairly spectacular view of something like a nebula or would the light be too diffuse by the time you got close enough to have a spectacular vista? (say I wanted to park a space station 15 LY from the Crab Nebula–I realize that we view it at being 5.5 LY in diameter but we’re looking at it as it appeared 6,500 years ago–I’m just speaking hypothetically here)

    • Rain says

      One way: when Voyager I and II drift pass the heliopause and the sun’s magnetic influence, i.e., when they are in true interstellar space, then their particle density measurements could provide a quantitative comparison of what the solar system’s vicinity is like compared to a typical nebulae region.

    • newSteveZodiac says

      15LY from a 5.5LY wide supernova remnant, swathed in synchrotron radiation from a radiating pulsar at its centre and the view would certainly blow you away.

  2. Beck45 says

    Don’t tell this to Star trek writers–that would mean the end of the franchise.

  3. But if you’re in interstellar space, it’s virtually perfect darkness anyway, so no one is going to see you.

  4. newSteveZodiac says

    So nebulae are nebulous? What a revelation.

  5. Astroraider says

    I guess that the Wing Commander games got it closer to right when they hid in asteroid fields … although I imagine that the depiction in the games wasn’t accurate. Even in the asteroid belt of the Solar System, asteroids aren’t very close together and certainly wouldn’t be packed together as depicted in Wing Commander. I suspect that we don’t see a lot of small debris from earth that may be present in the asteroid belt but we have sent numerous probes through that region without incident so it is pretty sparsely populated even so.

  6. kkt says

    Aw, spoil a nice plot device, why don’t you 😉

  7. Howard D says

    How would these people know? They haven’t been to a nebula. jk.

  8. Zoutsteen from Holland says

    science faction ruined my science fiction enjoyment a lot of times before. I think i can handle this again.

  9. zkank says

    Solar nebula is the nebula becoming denser, and continuing into a protoplanetary disk it’s denser still!

    With increasing heat and gravity through these progressions, I think there is enough there to rationalise it into a feasible hiding place! 😉

  10. John Stock says

    Transporters, energy shields and warp drives don’t exist either.. why point out just nebulae?

  11. Light_Horizon says

    Similar to how our solar system is in the middle of a minor arm of the galaxy. From a million ly away, it looks like we’re in a cloud, but to us, it’s just dark space.

  12. Turanga Leela says

    By this reasoning, Mars would be no brighter if you were in orbit around it than looking at it from Earth. The reasoning does not seem sound to me.

    • pollydextrous says

      Except that the brightness of Mars comes from light reflected by trillions and trillions and trillions of atoms per square centimeter. So the closer to Mars you get, the more your eyes will capture those photons. A nebula might have only tens of atoms per centimeter, your eyes would have a very hard time seeing the nebula no matter how close/distant you are from it.

    • Rain says

      Because nebulae are extended objects, Mars and (especially) stars are effectively point sources. So think about this and re-read what Williams say.

  13. DonH says

    The space photograph promulgators have only themselves to blame for the public’s misperceptions about phenomenon like this. We see all these pretty Hubble pictures, but the fact that our eyes would never see that image even if they were up close because you would still need to stare unblinking at it for several solid days is buried in the fine print. A majority of these may as well say ‘artist’s conception’.

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