The Dusty Path Toward Doom

By Phil Plait | October 17, 2005 10:51 pm

Yesterday, I talked briefly about what infrared images can tell us about dust in spiral galaxies. In a funny coincidence, the European Southern Observatory put out a press release today about a new image that discusses a similar topic! In this case, though, the arms lead down to a bottomless pit: a black hole in the center of a spiral galaxy called NGC 1097.

Galaxies are vast collections of stars, gas, and dust. At first glance, NGC 1097 looks like a fairly typical spiral galaxy:

Pretty, isn’t it? Our Milky Way would look a lot like that from a few million light years away, too.

Sometimes, this kind of galaxy is called a “grand design” spiral, because the spiral pattern is so big and obvious. But what’s interesting is what happens when you zoom in on the nucleus:

The blobby ring there is a circle of dense clouds of gas and dust forming stars. But if you look carefully, you can see that the dust inside the ring is forming a spiral pattern, and it looks like it’s swirling down into the nucleus! This image has incredible resolution, rivaling Hubble’s for seeing small objects. The astronomers then processed the image a bit to bring out faint details, and made this way cool image:

The dark ellipse is the region in the image where they enhanced it. With the brighter glow suppressed, you can actually clearly see the dust arms dropping right down into the center of the galaxy! And what happens there? Well, it’s too small to be seen in these images, but inside that galaxy, right at its very heart, is a supermassive black hole. It’s called “supermassive” because it tips the cosmic scales at about a million times the mass of the Sun. Even then, it’s kindof small for a galaxy’s central black hole. The one in the center of the Milky Way is four times that mass.

Anyway, that dust from the outer part of the galaxy core is falling into that black hole. As it falls in, it forms a disk called an “accretion disk”, which gets very hot. The disk is like a holding pattern for the gas, a place to pile up before it falls into eternity. Since the disk gets hot, it emits light. In some galaxies it gets very bright, outshining the galaxy itself — in those cases, the galaxy is said to be “active”). So ironically, even though black holes are known for gobbling down even light, they can power some of the brightest objects in the Universe!

Like I said in yesterday’s blog entry: studying the dust in a galaxy can tell us a lot about it, even about things we can’t see.


Comments (18)

  1. Thomas Siefert

    These pictures always envokes my childhood dreams of going there, of being up close.

    Imagine being at a distance of a galaxy where it fills your whole field of vision. Or on a planet in the center of a galaxy where stars are so plenty that the nightsky is like day light here on earth.

    I am just waiting for a science fiction movie that have enough imagination to actually take me there (and a 100″ TV to watch it on). For now I have to make do with pictures and my imagination.

    Of course, for now I would settle for a close passing comet or a nearby supernova in my life time (still want that TV though :-).

  2. Blake Stacey

    Maybe we’ll be lucky and Betelgeuse or Eta Carina will have blown up. The light might reach us tomorrow. . . .

  3. Samara


    A supermassive balck hole in the center of the galaxy – are we do to be sucked down anytime soon?

  4. Thomas Siefert

    To Samara:
    YES! we will have to get off this planet right now, do not bring any hand luggage :-)

    No, just kidding.
    Gravity is not like a drain in a bath tub where everything (minus long strands of hair) will sucked down.
    You should think of it more as the end of a vacuum cleaner tube, only nearby dust particles will be sucked up.
    I’ve tried this in my early years when my mum would make me vacuum my room, there is no such thing as a leave-the-vacuum-tube-in-one-spot-for-full-room-cleaning. Of course if you have a very powerful vacuum cleaner you could do the one-spot thing but the vacuum cleaner…. sorry… the black hole in the centre of our galaxy is not that powerful.

  5. The black hole in our galaxy is plenty powerful. We ARE getting pulled towards it and the galactic center in general, but we are orbiting it, so we aren’t getting any closer. Just like a satellite orbits Earth, the sun orbits the center of the galaxy. Satellites don’t come crashing down unless they slow down. (Low ones do eventually hit enough air molecules to do that, but that’s another story.) Slowing down the SUN would take a bit of doing! Don’t worry.

    Besides, even at the sun’s whopping speed of 220 kilometers per second (!) the galactic core is about 38 million years away.

  6. Nigel Depledge

    Dan, I think that the mass of the hundred billion or so stars in our galaxy kind of outweighs the 4-million-solar-mass black hole at its centre. We don’t so much orbit the central black hole as the centre of mass of all the billions of stars and the black hole combined.

  7. worse astronomy : the moon
    (sorry , but it’s tough being a musician !!!!)

  8. George

    Beautiful and amazing. :clap:

    It is interesting how the nucleous seems to be spiraling-in clockwise, while the galaxy seems to be spinning counter-clockwise. Huh?

  9. JusANuttaBackYahdah

    George…kinda like the way toilets flush in Australia…ROFL….
    Clear skies

  10. It reminds me of Irish Celtic “triskelion” three-part whorls in the illuminations from the Book of Kells.

  11. Kaptain K

    A few (possible) nit-picks. Please correct me if I’m wrong!

    “At first glance, NGC 1097 looks like a fairly typical spiral galaxy”

    Well, a “fairly typical barred spiral galaxy” anyway.

    “Our Milky Way would look a lot like that from a few million light years away, too.”

    While the Milky Way is a barred spiral, That looks like a SBa to me and I thought the MW is a SBb.

    “Sometimes, this kind of galaxy is called a “grand designâ€? spiral, because the spiral pattern is so big and obvious.”

    I thought “grand designâ€? spirals were more like M31 and M33 – Big, multi-armed and more circular than elliptical.

  12. George

    The counter-rotating core is not counter-rotating. The visible image shown is flipped (thanks to another Babber’s quick eye – cran) which causes the confussion.

  13. Kaptain K– assume a :-) goes with each point below:

    1) Barred spirals are still spirals.

    2) That’s why I didn’t say it would look exactly like it.

    3) To my knowledge, any spiral with big, well-organized arms is grand design. I’ll have to look into that more deeply. As long as they aren’t Intelligently Designed. Maybe they’re noodly instead.

  14. George

    [i]Intelligently[/i] Designed are barred. 😉

  15. Phil,

    First off, I simply love your blogin’s. You’ve shown me so much… so many huge and incredible things. Thank you for being here.

    This little posting is wonderfully profound, it sheds clear light on our OWN origins, and our certain fate. You made some very heady concepts most remarkably easy to understand.

    I blogged this post to under the title “Where We’re Heading.” on 20 OCT 05. I hope you get some traffic from us, as your site is MOST deserving of as wide an audience as possible. I hope I didn’t gush too much about you in my post.

    I sincerely find you one of the best teachers I’ve ever had to pleasure to know. Thanks again for being here… If my Astronomy Prof in College was even halfway as good as you, I’d have never missed a class. Because of you, I can actually work the Main Sequence of Stars in my head… and actually see them, in my mind’s eye, in all of their massiveness, floating in Space. When you show us a new star, I can classify it immediatly as I read the data you provide…

    So there’s my little testimony for you… What used to take me hours, laboring with pencil, graph paper and calculator… I now can do at a glance. Bravo Zulu, Phil! You tought an old, salty (Navy) dog new tricks!

    You kick Jack Horkheimer’s ass!


    -Tony B.

  16. Wow. I’m overwhelmed.

    I’m just doing what I have to do. It takes someone to listen, too, so don’t say it’s because of me. I’m just a match; you’re the firecracker.

    Oh– I met Jack some years ago at the first James Randi Amaz!ng Meeting. We got along pretty well. I have more hair than he does! But I don’t want to kick his ass. I just want his job. :-)


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar