Desktop Project Part 5: The mighty, mighty Dragonfish

By Phil Plait | March 30, 2012 7:00 am

[Over the past few weeks, I’ve collected a metric ton of cool pictures to post, but somehow have never gotten around to actually posting them. Sometimes I was too busy, sometimes too lazy, sometimes they just fell by the wayside… but I decided my computer’s desktop was getting cluttered, and I’ll never clean it up without some sort of incentive. I’ve therefore made a pact with myself to post one of the pictures with an abbreviated description every day until they’re gone, thus cleaning up my desktop, showing you neat and/or beautiful pictures, and making me feel better about my work habits. Enjoy.]

I’m fond of saying that the Orion Nebula is one of the biggest, most active star forming regions in the Milky Way galaxy. It has enough gas to form thousands of stars like the Sun, and it’s one of the brightest and closest such gas clouds in the sky.

But, it turns out, Orion is a piker. Or a pike. Because behold: The Dragonfish Nebula!

[Click to ennebulenate, or if you’re feeling frisky, grab the huge 7000 x 5500 pixel 26 MB version!]

The Dragonfish nebula — named for its resemblance to a terrifyingly toothy deep-sea fish — is, like its namesake, a monster. It’s something like 450 light years across… compare that to the Orion Nebula’s 12-15 light year width and you start to see how huge this thing is. It’s also incredibly massive: it may have a total mass exceeding 100,000 times the Sun’s mass, and may contain millions of stars!

Incredible. Even from other galaxies, it must be one of the most obvious features in the Milky Way. Yet, ironically, it’s very difficult to see at all from Earth. It’s located over 30,000 light years away, on the other side of the galaxy. There’s a vast amount of interstellar material (like dust) between us and it, absorbing its light, so in optical light it’s essentially invisible. But infrared light can pierce that fog, and the image above was taken using NASA’s Spitzer Space Telescope, designed to look in the infrared.

Astronomers used a different infrared telescope to look at the individual stars in the nebula, and found that it has an incredible 400+ O-type stars, the most massive stars that can exist. These stars are young, hot, massive, and blast out ultraviolet light. That’s what’s making this huge gas cloud glow, and in fact the cloud is expanding under the influence of the terrible flood of radiation. Worse, those stars will eventually explode in the next million years or so, one after another, blasting out radiation and material that will dwarf even what they’re putting out now. That will eventually tear through the nebula, ramming it, causing parts of it to collapse and form new stars, and other parts to dissipate entirely.

We’re safe where we are, tens of thousands of light year away. Too bad! In a million years, that’ll be quite a show.

Image credit: NASA/JPL-Caltech/Univ. of Toronto


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CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (19)

  1. Nigel Depledge

    Nice pic!

    Erm . . . if the nebula is “essentially invisible”, how did it come to be named for its resemblance to a deep-sea fish? Or is that it’s resemblance in infra-red light to a deep-sea fish?

  2. Fantastic… too bad we can’t see that in visible light here on Earth with amateur scopes. Even so, that’s great that we have the technology to spot it so we can all marvel at it.

  3. Mike Frontz

    “ennebulenate”
    nebula+enable+create?

  4. Eric

    If it’s 100,000 solar masses yet has generated millions of stars, does that mean the nebula is nearing the end of its life? Or does the cycle of star birth and death keep the nebula renewed with new material?

  5. Peter Davey

    In a million years, perhaps we – or whatever we will have become – will be better placed to view the fireworks.

    The science fiction writer, Stephen Baxter, once suggested that the place to really search for intelligence might not be in the comparativelty placid sections of the galaxy, such as our own, but in the more “dramatic” sections, where the pressure to evolve or be destroyed must be so much greater.

    On that basis, if we do take a closer look at the Dragonfish, I wonder what we might find, looking back?

  6. John H

    “…it may have a total mass exceeding 100,000 times the Sun’s mass, and may contain millions of stars…”

    So, given the portion of the mass tied up in the type O stars and the gas and dust and dark components, that leaves the average mass of the other stars in the object at much less than a tenth of a solar mass. Does that make sense?

  7. @ Peter Davey:

    I would suggest another reason for focusing on the “dramatic” places is the lookieloo factor. Everyone slows down to gawk at an accident. Perhaps the destruction of so many stars in so short a time will be considered a spectator sport?

    Maybe we should be listening for the interstellar equivalent of a vuvuzela.

  8. moregrey

    Dumb question: when you say “may have a total mass exceeding 100,000 times the Sun’s mass, and may contain millions of stars!”, to what mass are you referring? Are those millions of stars really tiny, or are you referring to the mass of the gas cloud?

  9. beer case

    If you read a bit in the PDF document, you’ll find this:

    “This verifies the presence of a OB association
    which, on the basis of source counts, is sufficiently luminous to powerits host star forming
    complex, giving it a total mass of 10^5M⊙
    and making it the most luminous OB association in
    the Galaxy.”

    That’s the 100,000 number.

  10. Lucas

    Phil, this is beautiful, but there is something I don’t understand:
    Is this picture IR or UV? You said it was taken by Spitzer in Infrared. But the you said it’s glowing because of the ultraviolet light it blasts…
    What is it?
    Thanks for showing us all the awesomeness in the universe :)

  11. amphiox

    I am presuming that the mass estimate for the nebula must not include the mass of the stars. Otherwise the average mass per star, at 1/10th, solar, would be barely above the lower limit for the smallest possible red dwarfs, and that, given the info about the giant O stars, would be nonsensical.

    (Unless they are counting brown dwarfs in the star count?)

  12. We’re safe where we are, tens of thousands of light year away. Too bad!

    LOL! You’d rather we were in grave danger? ;-)

    Very impressive object indeed & one I’ll admit I’ve never heard of before. Thanks. :-)

    Wonder how it compares to the Tarantula nebula in the LMC which I’ve read in a few places would be bright enough to cast shadows if it were as “close” as the Orion nebula or another vast star-forming nebula that’s found in Messier 33 – the Triangulum galaxy – called NGC 604 which spans nearly 1,500 light years and contains aroud 200 stars with 15-60 solar masses. (Click on my name for source. Read about it recently in an astronomy magazine but have forgotten exactly which one.)

    @6. John H :

    “…it may have a total mass exceeding 100,000 times the Sun’s mass, and may contain millions of stars…”
    So, given the portion of the mass tied up in the type O stars and the gas and dust and dark components, that leaves the average mass of the other stars in the object at much less than a tenth of a solar mass. Does that make sense?

    A hundred thousand times our sun’s mass makes for an awful lot of stars even O-type which rnage from 20 to 120 solar masses each. 100 O-type stars averaging 50 solar masses each – an estimate that’s probably too high* would be “only” 5,000 solar masses leaving plenty for other lesser stars to form from! ;-)

    I don’t think the BA said *all* million stars were spectral class O!

    ——————————-

    * because lowermass stars arealways more common than higher mass ones so I’d expect most O stars are more like 20 solar mass O9 variety than uber-massive 120 O3 ones.

  13. Messier Tidy Upper

    Continued : Actually the BA wrote :

    Astronomers used a different infrared telescope to look at the individual stars in the nebula, and found that it has an incredible 400+ O-type stars, the most massive stars that can exist. (Emphasis added.)

    So 400 x 50 which is probably an overestimate of the mass of the average O-type star here – given only a few will be the most massive O3 type and the majority probably 20~odd solar mass O9 stars – equals 20,000.

    So twenty thousand solar masses out of a hundred thousand solar masses leaves eighty thousand solar masses – plenty to spread around for lots of lower mass but still superluminous B type stars (4-20 solar masses apiece), lots of Sirian A stars (2 to 4 solar mass range), abundant Procyonese F (just over 1 to 2 solar masses) and solar mass G stars and oodles and oodles of orange, red and brown dwarfs with well under a solar mass each! ;-)

    Incidentally, in general overall terms O & B stars combined make up less than 1% of all stars and our relatively humble sun is perhaps surprisingly in the top 5% of most massive and luminous stars with 75% or so being red dwarfs, 15% or so orange dwarfs
    and 10% white dwarf stellar “corpses.”

    So if this rule holds true for this Dragonfish nebula there’s a rather staggering number of solar like suns there facing the perils of nearby destructive blue behemonths and regular suernova detonations. Fortunately for them, if they survive this early onslought and amanage to form exoplanets they’ve got much longer lives to lead and grow planets -10 billion year lifespans versus the fleeting mere millions of years the blue giants have to live.

    Unless I’ve got my maths wrong which is always possible but, kinda obviously, I don’t think I have.

  14. Messier Tidy Upper

    @ ^ MTU :

    Incidentally, in general overall terms O & B stars combined make up less than 1% of all stars and our relatively humble sun is perhaps surprisingly in the top 5% of most massive and luminous stars with 75% or so being red dwarfs, 15% or so orange dwarfs and 10% white dwarf stellar “corpses.

    D’oh! Ok, okay, I know that doesn’t add up a hundred percent. I was typing from memory and got it wrong. :-(

    (Goes to bookshelf, finds the right magazine and article)

    From Ken Croswell’s “Is there Life around Alpha Centauri?” article in Astronomy magazine, (Kalmbach publishing Co.) April 1991 issue, “The Galactic Pyramid” table / illustration.

    Make that :

    Red M dwarfs = about 70%
    Orange K dwarfs = about 15%
    White dwarfs = about 10%
    Solar G stars = about 4%
    Sirian and Procyonese A & F stars = about 1%
    All other kinds of stars (incl. W, O, & B) = Less than 1%.

    For clarity and getting the numbers to add up right! Sorry.

    So our Sun is far from being an average star and the blue giants visible like celestial lighthouses across the vast gulfs of space that speckle our night sky are very rare astronomical beasts indeed. Because it seems such high-mass stars are very hard for the universe to form in the first place and have astronomically brief lives when they are born.

    Of course, that article was written before we ‘d discovered a single brown dwarf star so spectral clases L & T were not included – assuming you want to include really super-successful hyper massive Jupiters as “stars” – and I think we’ve since found out that red dwarfs are even more abundant in reality than we used to consider them back then. So the exact percentages may have shifted slightly but I think the general idea of stellar percentages remains roughly true.

  15. Messier Tidy Upper

    Here’s a somewhat more recent and specific table of stars divided into spectral classes :

    Type O = 0.003 %
    Type B = 0.13 %
    Type A = 0.63 %
    Type F = 3.1 %
    Type G =8 %
    Type K = 13 %
    Type M = 78 %

    Source : page 89, “Ask Alan” column by Dr Alan Longstaff in ‘Astronomy Now’ magazine, Pole Star Publications, October 2006 issue.

    Note that this is only for main sequence “dwarf” stars – which are 90% of all stars – and thus does NOT include white dwarfs and supergiant and giant or brown dwarfs.

    BTW. Our Sun is still almost certainly within the top 5% of stars because as a G2 star it is
    hotter and brighter and more massive than the stars of classes G3 to G9 and beaten only b those of classes G0, G1 and some others from G2 such as the older and thus brighter Alpha Centauri A.

    I’ll leave it to y’all to work out the maths from that of how many of each spectral class there are in the Dragonfish nebula given the 400 approx. O-star figure! Anyone care to take on that challenge?

    (If it helps given the age of the nebula and presence of short-lived O-type stars, there won’t be any white dwarfs present to complicate the count!)

    @10. Lucas :

    Phil, this is beautiful, but there is something I don’t understand:
    Is this picture IR or UV? You said it was taken by Spitzer in Infrared. But the you said it’s glowing because of the ultraviolet light it blasts… What is it?

    I could be mistaken – and please correct me if I’m wrong – but my guess would be that the Ultra-Violet light is the energy source that causes some of the nebular material to glow in Infra-Red.

    Spitzer is an infra-red space observatory seeing the cosmos at those wavelengths, so, yeah, it wouldn’t be seeing the UV light (radiation) directly.

  16. amphiox

    The spectral class ratios may not necessarily apply to the stars in this nebula, as these numbers are derived for all stars in the galaxy, and part of the reason the big stars are rarer is because they live so much shorter lives, so they deplete out of the population quickly. I would expect that in an active star forming region the proportion of big stars would at least be a bit higher than the average.

    And again, to fit over a million stars into a 100 000 solar masses means an average stellar mass of 1/10th the sun, but 1/10th solar mass is just about the smallest of the smallest possible M type stars, so unless something is missing in the description, those numbers are impossible. Even a single O star would bump the average above 1/10 solar.

  17. Nigel Depledge

    Lucas (10) said:

    Is this picture IR or UV? You said it was taken by Spitzer in Infrared. But the you said it’s glowing because of the ultraviolet light it blasts…
    What is it?

    Yes. This particular pic shows us the IR emissions (mostly dust and gas and stars), but the nebula glows in visible light because it is being subjected to much UV radiation from the young hot stars and it fluoresces.

  18. Sam H

    This is nice – until now I had thought that Carina was (one of) the largest in the galaxy. Apparently only the biggest this side of the core…;) The Carina complex must still be pretty prominent from an extragalactic viewpoint, though :)

    @5 Peter Davey:
    The science fiction writer, Stephen Baxter, once suggested that the place to really search for intelligence might not be in the comparativelty placid sections of the galaxy, such as our own, but in the more “dramatic” sections, where the pressure to evolve or be destroyed must be so much greater.

    That is a very interesting point, especially considering the book I was flipping thru at the library yesterday (John Gribbin’s Alone in the Universe; essentially Rare Earth redux), which claimed that supernovae explosions and starbirth produce too much radiation to let complex life evolve. He repeated the Galactic Habitable Zone claim, but also added a tidbit I haven’t seen before when he suggested that until 5 billion years ago the rate of starbirth, supernovae and GRBs were too high to allow for the evolution of complex life (which he thinks is itself an extraordinary improbability, having something to do with the Snowball Earth period). IMHO this is an extraordinary lack of the imagination, but given the laws of empirical science + the fact that we still have only one sample (our own), then some of this makes sense. I personally think the GHZ doesn’t take into account the recent discovery of several metal-poor stars harbouring planets, or the possibilities of life being very resilient against radiation, but that up-till-5-bya claim I can’t really say anything on due to lack of knowledge – thoughts anyone???

  19. John H

    amphiox:

    My point exactly, the mass and quantity figures don’t make sense as they are presented in the article. Going back to the original paper, the 10^5 stellar mass figure is just for the OB association within the Dragonfish nebula and appears to have been incorrectly attributed to the entire nebula.

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