This is a picture of a jet of particles exiting the supermassive black hole in the center of Pictor A galaxy at nearly the speed of light. Source

This event is supposedly created from a black hole of 40 million solar masses. The full quote here:

The newly released picture shows the terrifying power of an actual supermassive black hole located in the galaxy Pictor A, some 500 million light years distant. This black hole is about 40 million times the mass of the Sun (that’s about 10 times larger than the black hole at the center of our own galaxy), and if it were to replace the Sun within our Solar System, its event horizon would swallow the orbits of both Mercury and Venus.

Now a quick search to Wikipedia would show a abundance of supermassive black holes many, many times larger than that supermassive black hole as well as a few that are around the same mass as that.

To my question: What set of special conditions that surround this particular supermassive black hole such that it is capable of creating this spectacular event?

Edit for clarity: By this I meant the jet and the hotspot.

  • 3
    $\begingroup$ Excellent question. I need an answer too. $\endgroup$
    – Nico
    Feb 9, 2016 at 10:21
  • $\begingroup$ Do you mean the jets, the lobes, or the hotspots? $\endgroup$
    – HDE 226868
    Feb 9, 2016 at 21:18
  • $\begingroup$ @HDE226868 I meant the jet and the hotspot. I'll edit the question to add that in. $\endgroup$
    – CipherBot
    Feb 10, 2016 at 0:09
  • $\begingroup$ Say, what is the site of the host galaxy in relation to this picture? I mean: is the picture a small central area of the host galaxy (how small?) .. or indeed is the galaxy itself merely a small central part of this photo? $\endgroup$
    – Fattie
    Jun 14, 2016 at 15:42

2 Answers 2


This is a clear example of an astrophysical jet, in this case, most likely a relativistic jet. In short, an accretion disk forms around a black hole (supermassive or otherwise). Matter is pulled towards the black hole and further energized, before being accelerated into a jet emanating from the black hole's poles. Two different mechanisms have been proposed for the formation of jets:

  • The Blandford-Znajek process requires that a magnetic field forms (from the accretion disk) that is centered around the black hole. Charged particles then move along the field lines, into jets. I recently wrote an answer about the details (see How does an accreting black hole acquire magnetic fields?). For this process to work, you need an accretion disk. It is generally considered the most likely explanation for black hole jets.
  • The Penrose process takes rotational kinetic energy from the ergosphere outside the event horizon and gives it to particles moving in jets. Note that this does not rely as heavily on the accretion disk as the Blandford-Znajek process does. For this process to work, you need a rotating black hole surrounded by some matter, likely in a disk.

The hotspot is, to me, much more interesting. It reminds me of structures seen around young stars: bipolar outflows (streams of gas that can form shock waves) and Herbig-Haro objects (the results of shock waves from relativistic jets. Obviously, the mechanisms are different, so no clear analogy can be drawn. But what is interesting about bipolar outflows and Herbig-Haro objects is that the shock waves produced therein result from collisions with the interstellar medium.

If a similar mechanism were to cause the shock waves by the hotspot, then we could conclude that the jets have hit the intergalactic medium. But I don't think this is necessarily the case, in part because of just how long these jets are prior to the formation of the hotspot. One would think that if the hotspot and shock waves are because of collisions with the intergalactic medium, the jets would be much shorter, because they would likely have reached higher density regions of it sooner. So that's why I find it interesting, and why I can't give you a good reason as to why the hotspot formed where it did, or the precise reason for it being there at all.

  • $\begingroup$ Thanks for the great answer. Would it be correct then to say: the hotspot is caused by the jet hitting "something" (perhaps the IGM, or something else) but we're not quite sure what... ? $\endgroup$
    – Fattie
    Jun 14, 2016 at 13:03
  • $\begingroup$ Is it a coincidence that the hotspot exists just where the shown radio-lobe ends? $\endgroup$
    – Fattie
    Jun 14, 2016 at 13:03
  • $\begingroup$ @JoeBlow Yes, it is likely correct that the jet is hitting something - possibly the IGM. No, it's not a coincidence that the radio love ends there; the end of the lobe is where it hits the IGM or whatever gas/plasma/dust/whaever it's colliding with. $\endgroup$
    – HDE 226868
    Jun 14, 2016 at 15:37
  • $\begingroup$ I can only say "duh" ! thx $\endgroup$
    – Fattie
    Jun 14, 2016 at 15:40
  • $\begingroup$ @JoeBlow No problem. I'm glad it helped. $\endgroup$
    – HDE 226868
    Jun 14, 2016 at 20:01

It's infalling matter, as described in the article:

The new image shows how the material being consumed by the black hole—stars, planets, interstellar gas, unwary astronauts (kidding)—releases a tremendous surplus of energy as it swirls around the event horizon in a massive accretion disk.

or in this article:

A huge amount of gravitational energy is released as material swirls towards the event horizon, the point of no return for infalling material. This energy produces an enormous beam, or jet, of particles traveling at nearly the speed of light into intergalactic space.

The infalling matter, mostly dust and gas, but also stars, is accelerated to nearly the speed of light. That's a giant amount of energy. Part of it is emitted as electromagnetic radiation.

The other factor is surrounding dust. If all this happens in a dense cloud of dust, you don't see it well from out outside.

Next: Are you sure, other supermassive black holes don't show similar features? Quasars near the edge of the visible universe are visible, since their respective jet points towards us.

  • $\begingroup$ I've edited the question a little to clarify what I meant. So to restate my edit: "By this I meant the jet and the hotspot." Thanks. $\endgroup$
    – CipherBot
    Feb 10, 2016 at 3:27

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