So yesterday I wrote about two supernovae in NGC 1316. This galaxy is way, way cool, and I wrote so much in the first draft (yes, I edit) that it was taking away from the supernovae. So I split off this bit.
To remind you, NGC 1316 is an elliptical galaxy, more or less, but it’s got some issues. It has another, smaller galaxy just north of it, and the two are in the very slow process of colliding. The dark dust lanes across its middle attest to that:
That’s a Hubble image of the central part of the galaxy. Those streamers of dust are pretty odd, and are a big clue that NGC 1316 started interacting with that other galaxy 100 million years ago or so. Elliptical galaxies don’t have a lot of dust, so that much sitting brazenly in the galaxy means it’s been visiting the galactic buffet table.
When a big galaxy eats a smaller one, sometimes there can be a shake up in the big galaxy. Gas and dust get tossed around, and a lot of it can fall into the central regions of the big galaxy. But as we all learned when we watched "Monster of the Milky Way", every big galaxy has a supermassive black hole in the middle. And even though you may think that black holes eat everything up around them, they actually don’t. As matter falls in, it forms a big disk and gets very, very hot. This can collimate (focus) twin beams of matter and energy that scream out of the vicinity at speeds approaching that of light.
These beams can do a lot of damage on their way out. Eventually, though, they lose energy as they ram their way through the gas and junk between galaxies, and they billow out, forming two huge Q-tip shaped lobes of matter. As it slows and cools, it emits radio waves, and so using radio is the best way to see them.
NGC 1316 is the poster child for this phenomenon. The latest collision dumped a lot of crap onto the central black hole, which responded by belching out a vast amount of gas. In radio waves, the picture is slightly different than the Hubble one:
This image is a composite of radio (in orange) and visible light images, and shows a lot more of the region around NGC 1316 than the Hubble image does. That Hubble image would only be a few pixels across in this image. The radio source from NGC 1316 has its own name: Fornax A.
I’ll note that this sort of thing is very common with interacting galaxies. In fact, many times when you see these twin lobes, it’s a sign that some cannibal is a messy eater.
The radio image makes this all very clear, but there is some indication of it in visible light too. But you have to take a way deep exposure. I found one:
Cripes, what a mess.
Like I said, there’s a lot going on in this system. Those two Type I supernovae, as amazing as they are, I think are pretty much unrelated to the rest of all this. It’s just a coincidence that such an active, violent galaxy has produced two supernovae that we see at the same time. We see lots of other galaxies just like this one– or worse– without simultaneous supernovae.
Also, those two supernovae may be thousands of light years apart; one blew up a long time after the other, but the other one was farther away. From our viewpoint, the light from the farther one caught up with the first one just as it blew up (think of it this way: it might have been 1000 light years farther away, but blew up 1000 years earlier). So it’s all just one big coincidence.
All in all, the only conclusion I can draw is that NGC 1316 pretty much hit the weirdness jackpot.
November 22nd, 2006 at 2:08 am
Those are amazing images. NGC 1316 is monumentally huge. Colossal! Hypothetically, if our little star and solar system existed somewhere within that massive elliptical galaxy, perhaps in the outer regions but still within NGC 1316, would we live out our existence basically unaffected by all the action around us? (Because we take up a small area, assuming we’re not near the super nova). Or – would we eventually find ourselves in hot water – i.e, too much radiation? Just curious. It’s a violent universe. Thanks for the interesting insights in your blogs.
November 22nd, 2006 at 3:38 am
BA,
Are you sure that the dust is the result of a previous encounter wit the smaller galaxy in the picture?
I ask because:
1) The smaller galaxy looks too much like an undisturbed barred spiral to have lost that much dust to its big neighbor.
2) To me, it looks like a more advanced version of Centaurus A, which is in the (final?) stages of digestion of another galaxy.
My impression is that the dust is the result of a previous capture of a galaxy, unrelated to the current interaction.
November 22nd, 2006 at 4:55 am
Great post:).
November 22nd, 2006 at 5:30 am
The latest collision dumped a lot of crap onto the central black hole,…
You meant to say crud, right? Otherwise, another enlightening post that brought a smile to my face – you may think NGC 1316 is “weird” but the supernovae are super cool! Keep us posted. (-8~
November 22nd, 2006 at 7:07 am
Anybody good enough at statistics to say what, if anything, this observation could say about the supernova rate in NGC 1316?
What are the chances of seeing an elliptical galaxy with two SNe at the one time?
Otherwise I think this is one for the News Item of No Scientific Interest bin. I mean, is any astronomer going to write a paper about this? I dunno, maybe there are interesting things you can do if you can get both of them into the same spectrograph slit…
November 22nd, 2006 at 7:39 am
BA,
Intersting stuff…….supernovae are intersting things to learn about.
Off topic a bit, Phil check out the Coast To Coast AM website from Monday. Richard Hoagland is pushing some crap and pictures about ancient ruins on the moon. I thought at first he was a crackpot, but between this and the “C-3P0″ Lunar robot pictures he has, I think he is just nuts.
November 22nd, 2006 at 7:50 am
These posts continue to impress me. Every time I try to explain science, I feel like I have to “begin with the beginning”, so I try to start with Galileo Galilei or even Democritus of Abdera. The BA’s concise and intuitive writing contains an awful lot of lessons, not just about science but about how to communicate science.
(Of course, there’s an advantage to beginning your history with Democritus, because the man had wisdom: “I would rather understand one cause than be King of Persia”, “A life without festivity is a long road without an inn”, and so forth.)
November 22nd, 2006 at 8:17 am
Great post!
What I’d like to know is, how long did it take to inflate those huge lobes of matter? I mean, at maximum speed, how long would it take to grow the lobes to their present day dimentions?
November 22nd, 2006 at 9:16 am
So if two concurrent supernovae in a single galaxy is merely coincidence, then how many would it take before we would suspect that there was more to it than simple chance?
Three? Four? Five? Depends on the precise locations and timing?
I ask because it would not be beyond the realms of possibility that a highly advanced civilization (one which had spread galaxy-wide) could use multiple supernovae as a kind of beacon to say “we are here”. Sure, it’s a very slow and inefficient way to communicate but stars are plentiful and there may be no better way to attract attention from as far as millions of light years away.
If it turns out that intelligent life is an extremely rare occurrence then a single civilization might be alone even in a vast eliptical galaxy and, like castaways stranded on a desert island, they could yearn to make contact with others no matter how far the distance.
It could also be a way of bootstrapping an escalating scale of communications — a pattern of exploding stars would certainly attract our attention, and if we observed such an event we would immediately start probing the host galaxy with every advanced instrument we have (and all those yet to come online), looking for some sort of signal. And perhaps we would find a radio signal that contained the information to allow us to build instruments to hook into some local InterGalacticNet we currently have no awareness of…
November 22nd, 2006 at 9:27 am
I wonder if the influx of gas and dust from the galactic collision might not have been a trigger event for the supernvae, ie, two white dwarves, sitting there, ALMOST ready to go boom and along comes a bunch of “crud” at near light speed, dumping more gas, just enough to tip the stars over the edge. I predict, there could well be more such events in that galaxy in the next few thousand years. If there is, just name the effect after me,,,
GAry 7
November 22nd, 2006 at 10:22 am
Kaptain K, I was surprised too, but the stuff I have read (like the Hubble press release linked in the supernova post) has been saying the dust is from the smaller galaxy, so I wrote that. I’ve been wondering if maybe there was a previous galaxy that got eaten, but I haven’t seen any papers about it. I may yet read some more about it.
November 22nd, 2006 at 11:18 am
What is this ‘dust’ made of? And where does it come from?
November 22nd, 2006 at 12:22 pm
If a large galaxy eats & digests another small galaxy, then where is the larger galaxy’s “poop-chute”, and what does the stuff coming out the chute look like? Is it all just brown dwarfs? Maybe NGC 1316 is suffering the mother of all stomach flu.
November 22nd, 2006 at 1:35 pm
^^^
Such unplanetary thoughts! 0-8~
November 22nd, 2006 at 2:16 pm
tacitus-
While the idea of detonating super-nova sounds technically possible for a greatly advanced civilization, it would also seem like such a waste. Assuming the c=top speed rule, then these stars are going to be the greatest source of energy in a civilizations immediate area, and therefore any civilization able to blow up stars is likely to be harnessing them for energy ( Type II civilizations on the Kardashev scale ). It would be analagous to us gathering all the fosil fuels on Terra (personal preference), putting them in one spot, and lighting the mother of all signal fires “just in case”. Gonna go with probably not on this one.
November 22nd, 2006 at 2:19 pm
tacitus-
While the idea of detonating super-nova sounds technically possible for a greatly advanced civilization, it would also seem like such a waste. Assuming the c=top speed rule, then these stars are going to be the greatest source of energy in a civilizations immediate area, and therefore any civilization able to blow up stars is likely to be harnessing them for energy ,Type II civilizations on the Kardashev scale. It would be analagous to us gathering all the fosil fuels on Terra, putting them in one spot, and lighting the mother of all signal fires “just in case”. Gonna go with probably not on this one.
November 22nd, 2006 at 3:07 pm
PeterV, dust is heavy elements created in previous supernovae. I think the generic term refers to a mix of light gaseous elements and solidified grains made of condensed heavy elements. In any case, “dust” is only visible because it absorbs light, so it appears dark against a bright background. A young galaxy is still full of dust and gas, but an old galaxy has seen all its dust condensate in planemos (planets not orbiting any star), brown dwarfs or red dwarfs.
So, other people, do I get it right?
November 22nd, 2006 at 3:11 pm
All this reminds me of the Known Space sci-fi universe of Larry Niven where the center of our own milky way is undergoing a chain reaction of catastrophic supernovae. The shockwave will reach the ficticious Earth in 20k years. I’m wondering what could possibly cause such a chain reaction… a supergiant black-hole merger creating a gravitational shockwave that would precipitate the collapse of surrounding stars? Wow, such imagination!
November 22nd, 2006 at 8:40 pm
Carl, interesting comments. As I mentioned in my previous comment, I would think that the supernova scenario would only be practical if the civilization had spread over an appreciable amount of the host galaxy. In that case, the use of a few thousands of stars in this manner, or even a million or two, in parts of the galaxy far enough away from the inhabited areas.
And it likely would only happen if the civilization had exhausted other avenues for detecting and communicating with other intelligent life in nearby galaxies. If civilizations are really so rare that only a small percentage of galaxies are host to a single successful intelligent species (I think not likely, but it’s possible) then what better way to advertise your presence than to light a few beacons that can be seen from half-way across the Universe?
Sure it would be a long shot, but if you’ve accomplished everything else as a civilization except make contact with another, then I suspect you might go to extraordinary lengths trying.
I agree it’s not likely, but you never know….
November 23rd, 2006 at 7:09 am
Yep, its an unusal galaxy alright but it does (as someone here already mentioned) remind me quite a bit of Centaurus A (Which also has an NGC designation that I can’t recall from the top of my head.)
I wouldn’t be rude about a galaxy that was so exceptional and showing such generosity with its supernova displays Phil!
I’d say it was a standout or exceptionally cool galaxy rather than a weirdo and as for the er..crud … it swallowed and ejected I think there are better ways you could phrase it.
After all we don’t want to hurt its feelings do we???
November 23rd, 2006 at 2:52 pm
Brings up a question: does anyone know what the killing range for a SN is? For eg, if Betelgeuse at 500 LY or so has already blown up, what is the outlook for this solar system?
November 28th, 2006 at 9:22 am
As an add-on to Gary’s idea, what do the jets from the core black hole do to stars in their path? Are those SNs in that path, perhaps?
It’s clearly been going on for quite some time, given the size of the plumes.