Heart and Skull nebula

By Phil Plait | April 7, 2011 7:00 am

I’ve been an astronomer a long, long time. Even so, I still sometimes get surprised at how different the same object can look when imaged in different ways. I just saw an excellent example of this… W5, aka the Soul Nebula:

[Click to ennebulanate.]

Pretty, isn’t it? It was taken by César Cantú, an amateur astronomer in Mexico. It’s not a true color picture. Not even close! For one thing, he used three filters which let through extremely narrow wavelengths of light (that is, the filters reject all light except for a very thin range of wavelengths; I’ve written about them before). Our eyes see broad ranges of colors, so immediately these filters change the very nature of the picture. Different atoms in space emit at different colors, and the filters he chose select for hydrogen, oxygen, and sulfur, which tend to emit light very strongly in gas clouds.

Not only that, he mixed and matched the colors. The hydrogen filter lets through red light, but he colored it green in the picture; oxygen is usually green but he made it blue*; and sulfur is red which he actually did color red. This throws off my usual sense of what I’m seeing in a picture (I really am used to hydrogen being red and oxygen green) so it forces me to re-evaluate how I see this gas cloud.

But more than that, when César said this was the Soul nebula I almost didn’t believe him! I’ve seen this nebula any number of times, including most famously as seen in the infrared picture here from the Spitzer Space Telescope (go to that link to see a much larger version). It’s tilted the other way, but if you look carefully you’ll see this is in fact the same gas cloud; look closely at the cusp at the top of the nebula in particular.

And I can’t help but laugh at the funny irony here: in the Spitzer image, W5 looks like a classic valentine, a heart. But in César’s picture it looks like a skull! It even has glowing eyes, like something right out of Halloween. Talk about contrast. The more I look at it, the creepier it gets. Yikes.

Of course, there’s science here. Stars are forming in this region of space, and the glowing eyes of the skull are actually where newborn stars are blowing strong winds and emitting fierce amounts of ultraviolet light. That acts to carve cavities in the gas, making what look like the eye sockets. In fact, the whole outline of the nebula is shaped by the winds from those stars.

So I guess there are many ways to see this same object: different filters, different colors for those filters, different wavelengths, different body parts as interpretations of the shape, and thinking scientifically instead of pareidoliacally. Which I think isn’t a word, but maybe is now.

Anyway, if you like this picture, go take a look César’s website where he has beautiful images of galaxies, planets, and other astronomical objects. And when you do, keep your eyes and your brain open. Who knows what you’ll see!

* For the pedants out there, the color emitted by an atom depends on other factors as well, like the temperature, the density, and how ionized the atom is. Oxygen missing one electron tends to emit in the blue, but an oxygen atom with two missing electrons emits in the green. It’s pretty complicated in reality, as the Universe is sometimes, so I’m simplifying here.

Related posts:

Happy cosmic Valentine’s day! (a gallery of heart-shaped astronomical objects)
A new old view of an old friend
An ionized rose would smell as sweet

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (18)

  1. Gary Ansorge

    Ah, pareidolia, from skulls to hearts to, well, anything. So much fun,,,

    In the following link, the author talks about bared vs spiral galaxies and how they may be mere stages in an ongoing evolution that repeats itself.


    Gary 7

  2. uudale

    Pretty cool. Looks like we have a new form of art here: Using filters to create different views of the same astronomical object.

    Astronomy as art!

  3. Creepier still… At the bottom of the blob to the right of the skull, is a hand holding one if its eyeballs. (I guess the other eyeball is floating away, towards the top-left corner of the image.)

  4. Thea

    You misspelled the word ‘sulphur’.

    And that picture is amazing. It looks like a green glow-in-the-dark skull!

  5. Roland

    I think it’s actually He-Who-Must-Not-Be-Named’s Dark Mark.

    It seems we’re doomed, yes.

  6. Chris A.

    @Thea (#5):
    Umm, not according to the IUPAC (as of 1990) or the Oxford English Dictionary: “In chemistry… the -f- spelling is now the standard form in all related words in the field in both British and US contexts.”

  7. DrFlimmer


    I am not a native speaker, but I would prefer pareidolious as the adjective and, hence, pereidoliously as the adverb. ūüėČ

  8. It’s either Invader Zim or Cthulhu. Ia! Ia! Cthulhu Fhtagn!

  9. Wow a nebula that looks like that must be a sign of something!

    Or not, whatever…

  10. RwFlynn

    I’m so glad you posted this. I’m (obviously, lol why else would I be here?) interested in Astronomy, and in the middle of learning Spanish so his website is perfect for me.

  11. Phil, as a fellow Trek fan I’m embarrassed for you. It’s clearly a Melkotian.


  12. Very interesting picture… the universe is such a beautiful place! Thanks for posting this pic.

  13. Svlad Cjelli

    Agreeing with DrFlimmer. Pareidoliacally is an ugly word, and the second “a” looks suspect. ūüėõ But, as Phil notes, yes it’s a word.

  14. Robert Carnegie

    British reprints of Marvel Comics used to occasionally have four-colour printing in the wrong colours. Spider-Man would be in green and the Incredible Hulk red, or something like that. Also, one time, Conan the Barbarian was captured by local tribesmen and tied hand and foot to a pole so they could carry him, like that bit in [Return of the Jedi], and this apparently confused the printer so the page was printed upside down. It hasn’t happened lately, they are probably using superior technology, but there is an actual “Red Hulk” character in stories now so I don’t rule it out.

    My current science-fiction read, [Absolution Gap], has so far revealed a green star, which the reader is expected to know is Wrong. It is a star where something bad has been done to it, or near it. Rather annoyingly, it is being told out of sequence so that characters in the book know exactly what it is, they were there when it happened, but we don’t, yet.

  15. Interesting photograph – I didn’t realize you could filter out colors (wavelengths) that specifically, although it makes sense as you would need to to determine what elements are on other stars, planets, etc.


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