S marks the spot

By Phil Plait | April 4, 2011 6:58 am

A few years back I was working on creating educational products for the NASA orbiting observatories Fermi and Swift. These look at super-violent high-energy objects like exploding stars and black holes gobbling down matter. All big galaxies have supermassive black holes in their cores, and some are sloppy eaters, spewing out vast amounts of energy as the material makes The Final Plunge.

I remember finding images of one such galaxy, simply called the Circinus Galaxy, and being baffled as to why I had never heard of it or could find so little info on it. It’s only 14 million light years away, close for a galaxy! Turns out, it’s heavily obscured to visible light telescopes because it happens to lie in the plane of our own galaxy, and we have to look through lots of thick dust to see it. That dims the light a lot! But infrared light can pierce through that dust, making this an interesting object at wavelengths invisible to the human eye, colors that happen to be the specialty of NASA’s WISE spacecraft. So when astronomers took a look, well, behold!

What an awesome picture! [Click to blackholenate.]

There’s a lot to see here. First, obviously, the galaxy’s core is incredibly bright! That’s from the huge amount of infrared energy pouring out of the nucleus. One source is the matter falling into the black hole; that stuff piles up into a disk that has a lot of gas and dust. Close in to the black hole it gets very hot and emits X-rays, but farther out it’s only warmish and emits infrared. Even farther out from there, light years from the core, there is a ring of stars being born in the galaxy, and they too blast out IR.

If you look closely, just outside the intense core, you can see a faint oval marking the galaxy’s spiral arms. That’s more obvious in the image here, which is from a ground-based telescope called 2MASS, for 2-Micron All Sky Survey, another infrared telescope. The orientation is the same (you can see some of the same stars in both images) and the galaxy itself is pretty clear.

In the WISE image, though, you can see two long, sweeping, S-shaped curves. Those are much larger spiral arms arcing out from the galaxy. They appear green in the WISE image because they are emitting at a wavelength of 12 microns, much farther out into the IR than 2MASS can see (in the WISE image, blue is from IR light at 3.4 microns, cyan at 4.6 microns, and red at 22 microns; for comparison, the reddest light the eye can see is roughly 0.75 microns or so). Usually, that wavelength comes from warm dust and long-chain organic molecules called PAHs, for polycyclic aromatic hydrocarbons — basically, smelly soot. This indicates the presence of young stars as well, since locations of star birth generally have lots of PAHs.

I mentioned that the region near the black hole is blasting out high-energy light as well. Here’s how this looks to the orbiting Chandra X-ray observatory (left), and Hubble (right):

The Hubble image clearly shows the spiral arms and some of the material blasting out, while the Chandra image shows that lots of powerful X-rays are being emitted as well.

By combining all these images, all these data across the electromagnetic spectrum, we get a much clearer picture — figuratively and literally — of this enigmatic object. Imagine! Until 1975, an entire nearby galaxy was hidden from our view! What else is out there, waiting to be found?

Image Credits: WISE: NASA/JPL-Caltech/WISE Team; 2MASS: S. Van Dyk (IPAC); Hubble: NASA/A.Wilson et al.; Chandra: NASA/Penn State/F. Bauer et al.


Related posts:

- A black hole wind is rising
- Evidence and theory collide with galactic proportions
- Taste my death ray, 3C321!
- Super zoom of galactic doom
- Voorwerp! (an object that looks much like Circinus)

Comments (13)

  1. Nigel Depledge
  2. Nigel Depledge

    The BA said:

    PAHs, for polycyclic aromatic hydrocarbons — basically, smelly soot

    Aw, Phil, fancy you falling for that one. Aromatic chemical compounds are not named for being, y’know, aromatic (although some of them smell pretty powerfully – yes, pyridine, I’m turning my nose up at you!). Aromatic compounds are a class of cyclic compounds that contain conjugated pi bonds (in addition to the more usual sigma bonds) and therefore have delocalised electrons. Admittedly, it’s more complicated than this in reality, but I’m simplifying here to save space*.

    * And, a bit, because my memory of molecular bonding orbital theory is a bit shaky.

  3. Usually, that wavelength comes from warm dust and long-chain organic molecules called PAHs

    10:1 that we see an abiogenic oil comment before this post is buried.

  4. Electro

    @Solius

    So thats what all those space probes are doing, I knew it!!!

    Ethane lakes on Titan? We’ll take those too.
    ;-)

  5. Phil – Jesus is out there, waiting to be found.

    No one’s tried scanning the holy ghost spectrum, have they?? Huh??

  6. The Barber of Civility

    ” What else is out there, waiting to be found?”

    Not “what”, but “who”.

    Amelia Erhart, Jimmy Hoffa, Bigfoot, Klingons, and Nessie (among many). (You DID ask!)

  7. Messier Tidy Upper

    Until 1975, an entire nearby galaxy was hidden from our view! What else is out there, waiting to be found?

    The Circinus galaxy isn’t alone in being a large nearby galaxy hidden behind the more crowded “Zone of Avoidance” for the Milky Way there’s also :

    http://en.wikipedia.org/wiki/Maffei_1

    the closest elliptical galaxy which would otherwise be prominent in our skies. It and its similarly hidden companion galaxy Maffei 2 were found in 1968.

    Mind you, I wouldn’t have thought Circinus :

    http://en.wikipedia.org/wiki/Circinus

    &

    http://stars.astro.illinois.edu/sow/tra-t.html

    was that obscured by galactic star clouds.

    I wonder if we have found everything hidden in this zone yet or not? Great post. :-)

  8. Messier Tidy Upper

    @5. gameshowhost :

    Phil – Jesus is out there, waiting to be found.
    No one’s tried scanning the holy ghost spectrum, have they?? Huh??

    I guess you’re joking there (right?) but the idea that what we consider the the “supernatural” could be part of an extended from of the “electromagnetic” (plus?) spectrum is one that has occurred and has a certain appeal to me. :-)

    Not saying its true or not, just a neat idea. ;-)

    Alternatively – assuming the big “if” that there is actually something to the “supernatural” (for want of a better word) phenomena – could they be related / emanting from one or more of the many other postulated extra dimensions or branes in that genuine cosmological theory thereof?

  9. Messier Tidy Upper

    Again, just a vague musing there & not claiming that things “supernatural” necessarily exist – or don’t.

    Brane theory link here :

    http://en.wikipedia.org/wiki/Brane_cosmology

    for those wondering about that reference.

    The other Circinus section via Kaler here :

    http://stars.astro.illinois.edu/sow/cru-t.html

    Plus the wikipedia entry on the Circinus galaxy here :

    http://en.wikipedia.org/wiki/Circinus_Galaxy

    Incl. a note that it’s the closest Seyfert galaxy and & active galaxy generally to our own. :-)

  10. Messier Tidy Upper

    @ 6. The Barber of Civility :

    ” What else is out there, waiting to be found?”
    Not “what”, but “who”.
    Amelia Erhart, Jimmy Hoffa, Bigfoot, Klingons, and Nessie (among many). (You DID ask!)

    If those “who’s” (& bunyips too? ;-) ) are out beyond our own Galaxy floating around in space they’re in big trouble indeed! ;-)

    Unless they’re on a rogue world like Mongo – in which case they’re in only slightly less trouble! ;-)

    Also they’ll be a little hard to spot even with the likes of Hubble.

    Also if “Nessie” is way out in space beyond our Milky Way then that’s disappointing news to a lot of Scots! ;-)

  11. Nigel Depledge

    @ MTU (10) -
    Nessie is alive and well and living in dozens of gift shops in Inverness.
    ;-)

  12. #11 Nigel:
    Not to mention his/her very own museum at Drumnadrochit!

  13. jkittle

    What is left to be found are any planets larger than Mars out at the distance of the inner oort cloud. Also nearby brown dwarfs!

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