Distant black hole poses for a close-up
Written by Anne Minard
1H0707-495
Astronomers have probed closer than ever to a supermassive black hole lying deep at the core of a distant active galaxy that was once thought to be shrouded in dust — which will greatly advance the look captured in this NASA file image from the mid-1990s. Using new data from ESA’s X-ray Multi-Mirror Mission (XMM)-Newton spaceborne observatory, researchers peered into the innermost depths of the object, which lies at the heart of the galaxy known as 1H0707-495.
“We can now start to map out the region immediately around the black hole,” says Andrew Fabian, at the University of Cambridge, who headed the observations and analysis.
Artist's conception of a black hole. Credit: ESA
The galaxy – known as 1H0707-495 — was observed during four 48-hr-long orbits of XMM-Newton around Earth, starting in January 2008.
X-rays are produced as matter swirls into a supermassive black hole, illuminating and reflecting from the matter before eventually accreting into it. Iron atoms in the flow can be observed in the reflected light, affected by the speed of the orbiting iron atoms, the energy required for the X-rays to escape the black hole’s gravitational field, and the spin of the black hole. All these features indicate that the astronomers are tracking matter to within twice the radius of the black hole itself.
XMM-Newton detected two bright features of iron emission in the reflected X-rays that had never been seen together in an active galaxy. These bright features are known as the iron L and K lines, and they can be so bright only if there is a high abundance of iron. Seeing both in this galaxy suggests that the core is much richer in iron than the rest of the galaxy.
Statistical analysis of the data revealed a time lag of 30 seconds between changes in the X-ray light observed directly, and those seen in its reflection from the disc. This delay in the echo enabled the size of the reflecting region to be measured, which leads to an estimate of the mass of the black hole at about 3 to 5 million solar masses.
The observations of the iron lines also show that the black hole is spinning very rapidly and eating matter so quickly that it verges on the theoretical limit of its eating ability, swallowing the equivalent of two Earths per hour.
Source: ESA. The paper appears in Nature.
Filed under: Astronomy, Black Holes
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May 27th, 2009 at 10:52 am
Nice that a busy BH tests BH theory ("limit of eating ability").
Cue PU 'explanations' for this limit and why this isn't a BH in … 3 … 2 … 1 …
May 27th, 2009 at 11:02 am
I'll go one further, Torbjorn Larsson OM.
Prediction: none of the PU/PC/EU comments made wrt this UT story will contain specific, quantitative, feasible suggestions on how the PU/PC/EU explanations of the observations described in the UT story could be tested.
I would *love* to be proven wrong on this prediction …
May 27th, 2009 at 11:30 am
It's really interesting what we can learn from spectra. This result is obtained by just analysing the K and L line of iron. One can read the velocity of the iron. One can see that the irons swirl around something, since the line is broadened at both sides of the "real" line. One can even see how fast the "central" thing is rotationg. I must admit that I don't know how one can do this. It would be interesting to read the paper – but it is published in Nature. I guess it will take some time until one can read it for free – I would be glad if it were otherwise…..
(There's a reason that I didn't use the term black hole – what else could it possibly be?)
May 27th, 2009 at 12:07 pm
Dr Flimmer, I think the astronomers measured the width of the two emission lines (especially blueward and redward wings on each side of the "real" L & K lines) to determine the speed of rotation. Interesting that strong iron lines are observed since this element must have only come from supernovae enrichment of the surrounding materiel . Haven't been able to find a pre-print or free copy of this paper, but will post a link if I can find one.
May 27th, 2009 at 1:47 pm
At least the ESA page says that they measured the rotational speed of the iron and the spin of the black hole. The first thing is of course "simple" Doppler shift (those lines can become really broade close to a black hole. But I wondered how one can determine the spin of the black hole. Most likely there is a specific effect on the line, but I don't know what effect that is (or I forgot about it….)
May 27th, 2009 at 2:20 pm
The paper is not even in ADS yet!
There are some earlier ones by Fabian et al. which report observations of other AGNs, and describe the techniques used (I think). Anyone interesting in links to those papers?
May 27th, 2009 at 2:59 pm
Um, I mean "carry an enrichment of iron".
May 27th, 2009 at 6:58 pm
Impressive work. Can't wait until these sort of innermost stable orbit observations become truly routine…
May 27th, 2009 at 8:13 pm
Excellent. This is a pretty direct observation of the near field region of a black hole outside the horizon.
The rotation of the black hole is estimated from the observation of speeds of the material around the BH. The closer in the faster material will orbit due to frame dragging. There are some pretty complicated calculation here with the Kerr metric.
Lawrence B. Crowell
May 27th, 2009 at 10:49 pm
Here on Earth, we use high voltage electric currents to produce X-rays, yet there is no mention of such currents in the article. How come?
Cheers, Dave.
May 27th, 2009 at 11:19 pm
is it possible to use red shift to find these so called black holes?
May 28th, 2009 at 1:31 am
"Here on Earth, we use high voltage electric currents to produce X-rays, yet there is no mention of such currents in the article. How come?"
Well for starters, the article didn't mention any of the creation mechanisms for the x-rays in question – it clearly wasn't written to go into that level of depth.
And yes – here on Earth, electric discharges are how we prefer to create x-rays. In this method, x-rays are produced when inner-shell electrons in atomic orbitals decay from an excited state. As an undisturbed atom will (almost) always quickly decay into the ground state, such constant de-exciting inner shell electrons must be excited to higher energy levels in the first place. The question is – what can cause these excitations? Well – electrons accelerated through a potential difference can cause such excitations in the constituent atoms of a target, as in X-ray machines on Earth. But this is far from the only mechanism of x-ray creation/emission…
X-rays can also be produced by brehmstralung, inverse Compton scattering, synchrotron radiation etc. I won't go into these because that would be lengthy – check out wikipedia or some other resource. Suffice it to say though that each mechanism has it's own characteristic emission spectrum that can be distinguished from others. The reason that the electric discharge method isn't mentioned in the article is that the processes just mentioned are expected to be far more important in the plasma environment around a black hole, and are observed to be.
May 28th, 2009 at 1:37 am
"is it possible to use red shift to find these so called black holes?"
In a way – yes. If you look at emission lines in the vicinity of a candidate black hole, one can see an enormous redshift immediately to one side of the whole and an enormous blueshift on the other, corresponding to the orbital velocity of the emitting material. From the magnitude of this shift, one can calculate the recession/approach speed of the orbital material in the immediate vicinity of the hole. Combining that with distance information to the galaxy in question and the angular resolution of the image, one can calculate the orbit of the material, and hence deduce the mass and size of the central massive object. This leads to but one piece of evidence that either falls in favor of or in opposition to a candidate black hole.
May 28th, 2009 at 1:39 am
…to one side of the whole… > …to one side of the hole…
May 28th, 2009 at 6:00 am
My comment is stuck in moderation since last night. Here it is withou the links:
@ Nereid:
LOL! I’ll think you passed the event horizon on that one.
@ Jon:
“this element must have only come from supernovae enrichment of the surrounding materiel .”
As someone on BA’s blog just remarked on iron and supernovae, isn’t iron the last element amenable for fusion, being the most bound nuclei? That would imply iron rich stars, and iron enhancement by stellar processes as well, wouldn’t it?
“When hydrogen is burning in the center of stars, the CNO-cycle remains closed, but in hotter environments, e.g. in Novae or X-ray bursts, a break-out of the reaction chain towards heavier nuclei becomes possible (Fig. 3).”
“The chemical elements heavier than iron can not be produced by fusion reactions. Since the binding energy per nucleon is decreasing past the iron group nuclei and because of the increasing Coulomb barriers, the nuclei heavier than iron are essentially synthesized by neutron capture reactions.”
I.e. wouldn’t the stellar wind of “hotter environments” carry iron?
May 28th, 2009 at 6:01 am
My comment is stuck in moderation since last night. Here it is without the links:
@ Nereid:
LOL! I’ll think you passed the event horizon on that one.
@ Jon:
“this element must have only come from supernovae enrichment of the surrounding materiel .”
As someone on BA’s blog just remarked on iron and supernovae, isn’t iron the last element amenable for fusion, being the most bound nuclei? That would imply iron rich stars, and iron enhancement by stellar processes as well, wouldn’t it?
“When hydrogen is burning in the center of stars, the CNO-cycle remains closed, but in hotter environments, e.g. in Novae or X-ray bursts, a break-out of the reaction chain towards heavier nuclei becomes possible (Fig. 3).”
“The chemical elements heavier than iron can not be produced by fusion reactions. Since the binding energy per nucleon is decreasing past the iron group nuclei and because of the increasing Coulomb barriers, the nuclei heavier than iron are essentially synthesized by neutron capture reactions.”
I.e. wouldn’t the stellar wind of “hotter environments” carry iron?
May 28th, 2009 at 6:40 am
davesmith_au's question (below) is a good one, and Astrofiend's comments address it well.
Let's look at this a little more deeply.
All astronomers have to work with is light (electromagnetic radiation, photons) from the sky.
At one level, all that astronomers do is find consistent patterns in that light, by location, by time, by photon energy (a.k.a. wavelength, colour, frequency), and by polarisation (and by various combinations of these).
So 'stars' are 'points' of light that move across the sky in a characteristic way; this is a shorthand term, and an empirical one to boot.
'AGN' (active galactic nucleus) is another such shorthand.
With physics that was increasingly powerful in terms of its explanatory and predictive powers came attempts to describe the various classes of astronomical phenomena (objects, events, etc) in terms of models; what a star 'really is' for example (note that, at this level, models can be very simple and purely qualitative – word pictures – or extremely detailed mathematical constructs, or anything in between).
The success, in scientific terms, of a model may be judged by its ability to account quantitatively for ALL the observed characteristics of the astronomical phenomena it claims to model, AND its internal consistency, AND its consistency with the relevant physics.
The current model of AGNs (the term is essentially an empirical description remember) is quite successful, judged by these criteria, but not 100% so.
In the unified model of AGNs there is a super-massive black hole surrounded by an accretion disc that is generally near its Eddington limit. Two jets emerge orthogonal to the disc, from the poles. A dusty torus surrounds the disc. And so on.
There are, at the highest level, two ways astronomers and astrophysicists could have got it wrong: 'AGN' may be heterogeneous (more than one type of 'thing', misclassified as only one), and the model may be wrong.
It happens all the time that a single object is misclassified – look at how many SDSS 'quasars' turned out to be 'stars' for example when spectra were taken – and that unambiguous classification is often difficult. However, discovering that a class is heterogeneous is a REALLY BIG THING (look at the implications of discovering that there are two classes of 'Cepheid', for example!), and does not happen very often.
OTOH, changes to models happen all the time; this is, in one way, what science is all about. Radical changes, of course, happen much less often, and are major events … think of the 1910s and 1920s (when 'nebulae' split into galactic nebulae and galaxies) or the Steady State vs Big Bang cosmologies.
So, back to davesmith_au's question.
One answer is "because no one has yet put forward a viable model of AGNs in which x-ray emission is due, at least in part, to that physical mechanism".
May 28th, 2009 at 8:04 am
Found a preprint version of the Fabian paper here: http://arxiv.org/PS_cache/arxiv/pdf/0905/0905.4383v1.pdf . @Dr. Flimmer, check out the last paragraph of page 4 of the paper (and especially ref.
for a more technical description of the the process of determining BH spin from x-ray spectroscopy. @Torbjorn Larsson OM, I agree with your description of iron being the 'end of the line' when it comes to nuclear fusion in the core of a star. My point was more that a supernova explosion is needed to liberate that iron from the stellar core and thus enhance the ISM.
May 28th, 2009 at 8:06 am
Ooops, that should be "( and especially ref. 8)"
May 28th, 2009 at 11:48 am
Btw: It is also possible to creat X-rays with heat. The gas (plasma) just has to be hot enough.
According to Wien's displacement law 2,9*10^6K would lead to a spectrum with its maximum at a wavelength of 1nm. So it is possible
May 28th, 2009 at 10:06 pm
excuse my change of topic but this seemed like a good place to ask. In the big bang theroy it talks of a sigularity that was unbelievably compressed, which eventualy expanded to the current size of our known universe. My question is, what if there was more than one singularity?what then would our "big bang" be called? a universe with in a multiverse?
also excuse any spelling mistakes.
May 28th, 2009 at 10:07 pm
excuse my change of topic but this seemed like a good place to ask. In the big bang theroy it talks of a sigularity that was unbelievably compressed, which eventualy expanded to the current size of our known universe.
My question is, what if there was more than one singularity?what then would our "big bang" be called? a universe with in a multiverse?
also excuse any spelling mistakes.
May 28th, 2009 at 10:07 pm
excuse my change of topic but this seemed like a good place to ask. In the big bang theroy it talks of a sigularity that was unbelievably compressed, which eventualy expanded to the current size of our known universe.
My question is, what if there was more than one singularity?what then would our "big bang" be called? a universe with in a multiverse?
May 28th, 2009 at 10:08 pm
excuse my change of topic but this seemed like a good place to ask. In the big bang theroy it talks of a sigularity that was unbelievably compressed, which eventualy expanded to the current size of our known universe. My question is, what if there was more than one singularity?what then would our "big bang" be called? a universe with in a multiverse?
May 28th, 2009 at 10:08 pm
In the big bang theroy it talks of a sigularity that was unbelievably compressed, which eventualy expanded to the current size of our known universe. My question is, what if there was more than one singularity?what then would our "big bang" be called? a universe with in a multiverse?
May 28th, 2009 at 10:11 pm
in the big bang theory it talk of a singularity.
What if there was more than one singularity? what then would our "big bang" be called? a universe with in a multiverse?
May 28th, 2009 at 10:12 pm
thanks for the answer
May 28th, 2009 at 10:15 pm
sorry my computer glitched out
May 28th, 2009 at 10:43 pm
iron, being a much heavier element than others with in most stars, when nuclear fussion occurs creating iron in a stars core marks the death of that star. then the star enters a super nova assuming of corse it is a high mass star. But when the supernova occured in this article wouldnt the iron from the core be ejected far out of the range of the black hole? why is there such a high concentration of iron being sucked in by the black hole ?
May 29th, 2009 at 6:54 am
While pondering Dr. Flimmer's question about how BH spin can be derived from xray spectra, I came across this 2009 paper (advocating a next-gen x-ray telescope IXO) entitled " Spin and Relatavistic Phenomena Around Black Holes" by Brenneman et. al. here: http://ixo.gsfc.nasa.gov/documents/resources/presentations/Decadal/Brenneman_spin_gravity_cfp_gct_ . This short paper describes several methods for determining BH spin from close measurement of iron lines in the x-ray spectrum and also has a couple great illustrations and an animation of an MHD model of an accretion disk and it's iron-line variability. Quite an interesting paper!
May 29th, 2009 at 7:11 am
Sorry, looks like the above link won't ! Really a great paper, though, well worth checking out. The 2006 paper by Brenneman and Reynolds "Constraining Black Hole Spin via X-ray Spectroscopy" can be found here: http://arxiv.org/abs/astro-ph/0608502 . This paper outlines the authors 'kerrdisc' model for x-ray spectra of black holes that takes into account relatavistic effects near the inner edge of the accretion disc. What's cool about their model is that it works on BHs of all sizes: stellar mass, intermediate, and SMBHs.
May 29th, 2009 at 7:35 am
Concerning the iron abundance of this galaxy, the 2009 Fabian paper states that the iron abundance is 9 times the solar value with other elements measured at solar values. They speculate "Perhaps a dense nuclear star cluster has led to the formation of massive white dwarf binaries which have enriched the nucleus with SN Ia ejecta rich in iron" (pg. 3). @ secondguess, the iron mentioned in the article and paper comes from the many heavy stars orbiting the super massive black hole that have gone supernova, thus spewing the bulk of their iron into the gas and dust swirling around this SMBH.
May 29th, 2009 at 8:00 am
"Spin and Relativistic Phenomena Around Black Holes" by Brenneman et. al. can be found here: http://arxiv.org/ftp/arxiv/papers/0902/0902.4691.pdf . Check out the animation and illustrations on pg. 6. The paper goes into detail about why black hole spin can be used as a forensic tool to gauge the mechanism(s) of galaxy formation. This is a great overview paper about the subject and where this field is heading. Fascinating stuff!
May 29th, 2009 at 9:37 am
Interesting and fascinating, indeed. Thanks a lot, Jon Hanford.
We are getting close to the event horizons. Times are beginning to become interesting