What does a nebula look like up close?

By Phil Plait | April 26, 2008 9:00 am

A while back, during one of my video live chats, I was asked what star I’d like to see up close. That’s a good question, so I recorded my answer. It morphed into a discussion of what a nebula, an interstellar gas cloud, would look like if you traveled up close to one. Here’s the video:

I’m doing another live chat on Sunday! If you have any questions, ask them then, and maybe I’ll do a video of them, too.

CATEGORIZED UNDER: Astronomy, Video Blog

Comments (35)

  1. We’re sorry, this video is no longer available.

  2. Taysine

    It’s coming up that the video isn’t there for me too.

  3. And “Here’s the video” link goes: “This is a private video. If you have been sent this video, please make sure you accept the sender’s friend request.”

  4. BA.
    Clicking on the hyperlink gives that ‘this is a private video’ and need to have an ‘invite’ to view it.


  5. Moog

    Only your friends can see it BA :)

  6. That was really odd. I uploaded it as public! Not sure why that happened. Well, it’s fixed now. Sorry.

  7. That is actually a known YouTube glitch where public videos appear private. The fix is to make them private then public again. There’s other glitches where videos become unavailable or comments take a couple of hours to appear.

    So I guess the question becomes: How do we know that we’re NOT in a nebula right now?

    (ps–Brown Dwarfs are cool, but not as cool as brown pygmies – har har!)

  8. Bill Bones

    Ah, I am vindicated! I KNEW they would be almost invisible from the inside and too faint to be worth a look from a short distance…!

    As I am not a rancorous person, I am not going to clog anyone’s e-mail adresses with this video, although they deserve so for trusting Star Trek’s visual FX team over common sense and the reality of what nebulas are…

    I will just send the link to this video as a late Xmas gift instead! (wicked smile).

    (Seriously, it’s like if people had an issue with clouds. Some people won’t believe it neither when you tell them that being inside a cloud is exactly the same as being inside fog -as fog and clouds are exactly the same thing!)

  9. John

    I’d opt for Eta Carinae…..but not too close 😉

  10. Yeah, I never did the math but I had a feeling it would be like that. I always have a sense of “bah” when I see one of those pretty space illustrations (or film footage… worthy of a few BA items, no? Star Trek, for one, is full of that crap) showing a crescent planet with a neat nebula in the background and often with its star shining from the wrong place relative to the phase of the crescent.

    Still, if your planet is a few light years away from one such nebula, you might be able to see it (the nebula, I mean). Probably much, much dimmer than what is usually shown in those illustrations, and certainly way too dim to be visible together with all the light that is reflected by your typical earth-like world (not to mention its star), but visible in a dark sky as a tenuous glow apparently coming from a large chunk of the firmament.

    Am I right?

  11. Mind you, this is only for planetary nebulae. The view inside, say, the Orion Nebula would still be fantastic. That’s because it has far denser regions, and filaments which would be bright enough to see.

  12. So are we inside one now then? Could we tell?

  13. KC


    Glad you mentioned the Orion Nebula. That one popped into my mind while you were talking about planetary nebula.

    As for stars, I think it would be neat to get a better view of Cygnus X-1.

  14. Hm… I’m skeptical even with reflection nebulae. The point is: if, when shooting photos of planets, they are so bright that you are unable to see even the brightest of stars, how on Earth would you be able to see light that is reflected in interstellar gas after being emitted by the very same stars you can’t see in the first place?

    Again, I didn’t do the math, but my gut feeling is that you won’t. There’s no way you could see at the same time the planet *and* the nebula, except, perhaps, if the planet is a thin crescent.

    On the other hand, if your planet is inside the Orion’s nebula, the brightest stars in your sky would be the Trapezium stars, way brighter than Sirius. But would they be able to match the brightness of an Earth-like planet?

  15. Nigel Depledge

    I think there are a couple of things that you could have mentioned but did not, BA:

    1. When we point a telescope at a planetary nebula, we are looking at the cumulative light from the entire depth of the nebula material. If you were inside the nebula, the light reaching you would only be from half as much material. (Plus, as you did sorta mention, if you were inside it, that light would be spread over the whole sky whereas we see it concentrated in a small are).

    2. Exposure time. The ring nebula has all these pretty colours and superb structure, when taken with an exposure of – what? – about an hour or so. When you look at it through a telescope, it’s just a little ring-shaped fuzzy grey thing (which I once saw occulded by a power line!).

  16. Patrik

    BA you probably know this but just to clarify, while it would be amazing to observe the Orion nebula upclose, the nebula wouldn’t be any brighter since surface brighness is independent of distance for non-pointlike objects.

  17. Chip

    I think its OK that occasionally, some SciFi shows (B5) show nebulae closer but still outside and from a distance. From the outside, if not too close you’d see something there, even if a faint cloud. Other than inside a planetary nebulae, in other types of gas clouds that have bright forming stars and star birth within, as the BA mentioned, you would find a very interesting view.

  18. lorna

    Thanks very much. Planetaries are my favorite DSOs, and they are pretty great looking in my scope (just an 8-incher), but looking only white. I never ever saw them as blue-green, though some folk do–thus the name–but on the other hand, I see the Helix as very bright and it’s supposed to be faint according to all my books, and I have no idea what people are talking about when they call M76 faint, for it’s a super-bright little gem to me. But it’s the Hubble images that make these so darned lovable. I simply thrill to the reality of certain ions regaining their electrons and putting out specific colors/wavelengths as the electrons cascade down through the energy levels. (How Bohr came up with the idea of discrete energy levels to atoms is still amazing to me–it seems like such an great leap forward.) Doubly ionized oxygen emitting in the blue-green, hydrogen in red is nearly as cool as black body radiation curves and maximum points of the curve making stars their various colors.

    It is SUCH a cool universe.

  19. Nebulae are often many light years across, so although you wouldn’t see colorful clouds of gas and dust up close from within, I think you would see the nether regions as such.

    Also, were taking human eyesight as being the Absolute. Night vision ‘scopes and other animals’ eyes see a different world.

    Perhaps, after 100K+ years as a space-faring civilization our eyesight will evolve, too.

    Kim Poor
    Former space artist

  20. John Hart

    Would be cool in the future if they could add the needed bio parts for our eyes so that by just blinking we could switch to different light frequencies or a combination to get hubble vision.

  21. Bob

    BA, what kind of density are we talking about? Molecules/atoms per cubic foot? Per cubic mile?

  22. I’ve read that observing using a roughly 4 to 6 inch newtonian with a ~30mm eyepiece approximates the sort of tenuous view of nebulae that one would get if they were nearby.

  23. “the universe isn’t built to make us happy”

    best quote ever!!!

    cheers from Buenos Aires, Argentina!!

  24. Andy Mak

    Yay! Scarlett Johansson! I wanna see her up close to!!!

  25. Quiet Desperation

    Can’t someone just model this on a computer somewhere already?

    “the universe isn’t built to make us happy”

    Then we should remake it in our image. :) I’ll start by modifying my little corner of reality. I’ll just twaek this- oops! I collapsed the false vacuum. Oh sh-


  26. Tony Webster

    This video prompted me to think about a similar issue – what would it be like to be in the middle of a globular cluster like M 13? I haven’t done, nor am I capable of doing the maths, but I hypothesise that the night sky might be so full of starlight that you wouldn’t be able to see individual stars and wouldn’t be able to see beyond the cluster. Now, if these are some of the oldest stars in the galaxy the possibility of life being around at some stage ought to be strong. But if so and if it was intelligent life perhaps the urge to look outward might not have arisen because there would be nothing to see. The inhabitants might be able to do astronomy outside the visible spectrum but might not have the motivation to do it.
    Does this sound sensible?

    As for the universe “not being made to make us happy” – made implies a maker and I’m not sure that’s a path you really want to go down!

  27. Brown

    The first time I saw the Ring Nebula was through a large telescope near Riverside, Iowa (Trek fans, take note). As Nigel Depledge said, “When you look at it through a telescope, it’s just a little ring-shaped fuzzy grey thing.” Unlike textbook pictures, the Ring Nebula had no reds, no greens, no yellows, no color at all. The Ring Nebula basically looked like a smoke ring.

  28. Dziban

    I seem to recall more instances of your math being wrong (forgot to carry something, didn’t translate from scientific notation correctly…there’s been a few of them) than right, BA, so how can I trust your assertion that you “did the math”? For all I know you calculated how many Cheerios are in a box on average. 😛

  29. Thanny

    BA misspoke about how telescopes work. When you look at a nebula through a telescope, you are seeing it dimmer than with your naked eye. The higher the magnification, the dimmer it appears.

    The telescope objective collects more light, but as magnification goes up, it spreads that light over a larger area. When the magnification equals about 1/7th the aperture in millimeters, the image will be as bright as it can be – pretty much equal to naked eye brightness, with light loss due to scattering and absorption subtracted.

    This is true of any extended object, including nebulae, planets, and most galaxies. Only when the image source is too small to be resolved, and appears to be a point, will the telescope actually make it brighter. That’s the case with stars, where all the additional light collected (over the naked eye) is focused on the same area, instead of being spread out. Increasing magnification actually makes the star brighter, too, since the atmosphere ( a very dim extended image) becomes darker. Until your aperture goes so high that the star becomes resolved into a disc, that is. After that, increases in aperture no longer make the star brighter than the largest aperture that still leaves it a point source.

    I’m sure Phil knows all this, but his comment in the video about collecting more light to make things brighter leaves the wrong impression.

    The real secret to making nebulae and other extended objects fantastically bright and interesting to look at is extended exposure, as someone else pointed out. Our eyes don’t work that way.

  30. MandyDax

    Phil, that was wonderful 😀 I started giggling part-way through when you were holding the book up to show us the nebulae you were talking about. It’s just that you reminded me of a friend’s kid who likes to show people his picture book of big trucks. “And this is a fire truck, and this is a dump truck, and this is a bulldozer. That’s my favorite.”

    On a more serious note, it really makes sense, even without the math, that you wouldn’t see much from inside a nebula. When we photograph these using long exposures and special filters, it appears as a ring, but it’s really a spheroid shell, and we only see the edges where it’s the thickest. The shell’s still there within the image of the ring, but it’s not visible. (I think of this as where it would be densest if we compressed it into a 2-D plane perpendicular to the line of sight, which is kind of what a photo of a tenuous nebula would tend to be.) Also, turn the pic of the Eye of God 90° and it looks for like the Eye of Sauron. ~_^

    My pick for star to visit would be… Betelgeuse comes to mind first, but at the point where it goes supernova. Of course, that’s up-close study of it as it’s entering the end of its life, and then time-dilated, invulnerable ship to study the supernova itself over the course of however long it takes to get good readings of all of what’s going on. (Since this journey is fiction, I decided I’m an Astronomer studying the hard data up close and personal, with all the gear that can survive a supernova and gather data without getting destroyed in the process.) It’ll make a spectacular show for you us Earthlings when it goes.

  31. Clair

    I am a perfect example of the lesson learned. I’m much better looking from far away than up close!


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