IGR J17091-3624: NASA’S Chandra Finds Fastest Wind From Stellar-Mass Black Hole


Chandra observations have found the fastest wind ever coming from a disk around a stellar-mass black hole.
This record breaking wind is about 20 million miles per hour – about 3% the speed of light.
This wind may be carrying away much more material than the black hole is actually capturing.
This artist’s impression shows a binary system containing a stellar-mass black hole called IGR J17091-3624, or IGR J17091 for short. The strong gravity of the black hole, on the left, is pulling gas away from a companion star on the right. This gas forms a disk of hot gas around the black hole, and the wind is driven off this disk.

New observations with NASA’s Chandra X-ray Observatory have clocked the fastest wind ever seen blowing off a disk around this stellar-mass black hole. Stellar-mass black holes are born when extremely massive stars collapse and typically weigh between five and 10 times the mass of the Sun.

The record-breaking wind is moving about twenty million miles per hour, or about three percent the speed of light. This is nearly ten times faster than had ever been seen from a stellar-mass black hole, and matches some of the fastest winds generated by supermassive black holes, objects millions or billions of times more massive.

Another unanticipated finding is that the wind, which comes from a disk of gas surrounding the black hole, may be carrying away much more material than the black hole is capturing.

The high speed for the wind was estimated from a spectrum made by Chandra in 2011. A spectrum shows how intense the X-rays are at different energies. Ions emit and absorb distinct features in spectra, which allow scientists to monitor them and their behavior. A Chandra spectrum of iron ions made two months earlier showed no evidence of the high-speed wind, meaning the wind likely turns on and off over time.

Fast Facts for IGR J17091-3624:
Credit Illustration: NASA/CXC/M.Weiss
Category Black Holes
Coordinates (J2000) RA 17h 09m 07.92s | Dec -36° 24′ 25.20″
Constellation Scorpius
Observation Dates 2 pointings on Aug 1 and Oct 6, 2011
Observation Time 16 hours 40 min
Obs. IDs 12405, 12406
Instrument ACIS
References King, A. et al, 2012, ApJ, 746, L20; arXiv:1112.3648
Distance Estimate About 28,000 light years
Release Date February 21, 2012

Abell 520: Dark Matter and Galaxies Part Ways in Collision between Hefty Galaxy Clusters

A clump of dark matter has apparently been left behind after a violent collision of galaxy clusters.
This dark matter clump contains far fewer galaxies than would be expected if the dark matter and galaxies hung together.
Astronomers used Chandra, Hubble, and the Canada-France-Hawaii, and Subaru telescopes to observe Abell 520, which is 2.4 billion light years away.
This latest result agrees with a similar conclusion that was announced in 2007.

This composite image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520, formed from a violent collision of massive galaxy clusters that is located about 2.4 billion light years from Earth.

Data from NASA’s Chandra X-ray Observatory show the hot gas in the colliding clusters colored in green. The gas provides evidence that a collision took place. Optical data from NASA’s Hubble Space Telescope and the Canada-France-Hawaii Telescope (CFHT) in Hawaii are shown in red, green, and blue. Starlight from galaxies within the clusters, derived from observations by the CFHT and smoothed to show the location of most of the galaxies, is colored orange.

The blue-colored areas pinpoint the location of most of the mass in the cluster, which is dominated by dark matter. Dark matter is an invisible substance that makes up most of the universe’s mass. The dark-matter map was derived from the Hubble observations, by detecting how light from distant objects is distorted by the cluster galaxies, an effect called gravitational lensing. The blend of blue and green in the center of the image reveals that a clump of dark matter (which can be seen by mousing over the image) resides near most of the hot gas, where very few galaxies are found.

This finding confirms previous observations of a dark-matter core in the cluster announced in 2007. The result could present a challenge to basic theories of dark matter, which predict that galaxies should be anchored to dark matter, even during the shock of a powerful collision.

Fast Facts for Abell 520:
Credit NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University)
Scale 8.5 arcmin across (about 5.4 million light years)
Category Groups & Clusters of Galaxies
Coordinates (J2000) RA 04h 54m 03.80s | Dec +02º 53′ 33.00″
Constellation Orion
Observation Date 7 pointings between Oct 10, 2000 and Jan 11, 2008
Observation Time 148 hours 38 min. (6 days 4 hours 38 min)
Obs. ID 528, 4215, 7703, 9424-9426, 9430
Color Code Optical (Red, Green, Blue); X-ray (Green); Mass (Blue); Luminosity (Orange)
Instrument ACIS
References arXiv:1202.6368; Jee, M. et al, 2012, ApJ 747, 96
Distance Estimate 2.4 billion light years (z=0.201)
Release Date March 2, 2012

Everything you do will help us

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I’m Jill Tarter, the Director of the Center for SETI Research.  Since we launched at TED last Wednesday, I’ve been reading what you’ve been writing.  There have been a bunch of comments on SETILive about not knowing what to do or what to mark or whether you are getting it right. We’ll work on making the tutorial more accessible and more informative as you’ve suggested, and over time we will implement some better marking tools as you’ve requested – but the ‘getting it right’ part is a bit more dicey.  That’s because we really don’t know yet exactly what ‘right’ is.

As Lou Nigra (thanks, Lou!) and the tutorials have described, the SETILive data that are coming from the ATA originate in the crowded bands; small portions of the terrestrial microwave window that we have historically skipped over.  That’s because our SonATA system gets confused there – it detects LOTS of signals, but it cannot finish clustering them, and classifying them by comparing them to signals that are detected in the other two (or maybe one as is now the case) beams on the sky being observed simultaneously, or finish looking them up in a database of all the signals that have been tagged as RFI in the past week.  Rather than conduct our observations with non-uniform sensitivity, or continuously restart software modules that have given up in exhaustion, we have chosen to ignore these crowded bands – at these frequencies we’ve been blind and deaf.  Ultimately that might turn out to be the best strategy – after all, why are those bands crowded?  They are crowded because they have been allocated to different types of terrestrial communications services.  We are the ones making all those signals.  Or are we?

IF (of course it’s a huge if) there is a technological civilization near enough to us – its distance in light years is less than half the time over which our technology has been transmitting at a particular frequency band – perhaps that civilization has noticed that the Earth is very ‘radio bright’ at certain frequencies. Perhaps it has transponded back a reply at the same frequencies, knowing that we would have receivers that work there.  A bit more speculation suggests that their message may be crafted to be detectable against this background of terrestrial transmissions.  With this scenario in mind, we could try to code and implement all sorts of clever, non-linear anomaly detectors that inter-compare the signals received from the multiple beams on the sky – but remember we are trying to do this in near-real-time.  The detector has to finish this task significantly before the observations move on to the next frequency band, because the system still needs to match whatever the detector has found against recently detected RFI from other directions on the sky.  We don’t know what we are looking for, but we do want to invoke logical constraints that insure that the signal is only coming from one direction on the sky and not many.

Before we throw a whole lot of new computing resources (that we actually don’t happen to have) at this problem, we should take a look at what’s actually going on in the crowded bands as a guide to what might be the most effective strategy – that’s where you come in!  We are hoping to use the amazing pattern recognition of your eyes and brains to look for signals (patterns of some sort) that appear in only one beam and not in any of the others.  We hope you can help us set up a sort of rogues’ gallery of signal patterns detected over the past week (fortnight, month, 3 days ??) that can be collectively ‘remembered’ to assess whether this particular signal pattern has been seen before from other directions on the sky. That’s why we want you to mark the RFI in multiple beams as well as any pattern that only shows up in one beam.  And then if enough of you mark the same single-beam pattern (so we are fairly confident it’s real, not noise), we’ll decide that it’s an interesting candidate signal and follow up on it immediately.  That means that instead of moving on to the next frequency in the observing sequence, we will reobserve in the same directions, at the same frequency.  SonATA is still blind, so you will have to tell us whether the pattern persists – is it still there?  Is it still only in one beam?  If so, the next observation will observe at the same frequency, but looking at different directions.  Is the pattern still there? Well, that’s too bad, it means it really was some form of interference and isn’t associated with the target we were pointing at on the sky. BE PREPARED – WE THINK THIS WILL HAPPEN A LOT.  Just like your eyes have peripheral vision, a radio telescope has ‘sidelobes’ into which signals can scatter and be confused with signals entering from the direction the telescope is pointing.  The sidelobes are complicated in the way they cover the sky; it may appear that a signal is coming from only one beam out of three, but moving ‘off source’ can reposition the sidelobes so that the interference is once again detectable.

But what if the signal/pattern persists when we reobserve ‘on source’, and disappears when we go ‘off source’? That’s getting interesting! We’ll start up a cycle of ‘ons’ and ‘offs’ that will stop when the signal fails to be detected, or not be detected, at the right time, or when we’ve completed five cycles.   If the system successfully completes five cycles, then the team at the Center for SETI Research will be alerted and we’ll be right there with you using our eyes and brains to figure out what to do next.  Since we’ve begun SETI observing on the ATA this has not happened in the less crowded bands that SonATA has been exploring automatically.  Now that we are trying to probe the crowded bands, we’ll have to see how it goes.

By now I hope you are convinced that your efforts can only help us.  There’s a slight chance that you just might discover a signal from another technology buried underneath all the terrestrial interference and we will all celebrate.  But at the very least you’ll help us better understand what it is that humans are doing as they manage to look at complex patterns and isolate sub-patterns that are unique to one of multiple samples.  There may well be neurologists or psychophysicists out there who already know that answer, but my team doesn’t.  If we can learn from you, we can be better equipped to train future automated detectors.  And if it turns out that this is not a task at which humans are particularly adept, well we haven’t lost anything.  After all, our previous strategy was to ignore the crowded bands.  There is only an up side to your participation.

Thanks for being willing to help out, and good luck!

5 March 2012 by