Spitzer sees star spew spurious spouts

By Phil Plait | April 4, 2011 5:25 pm

Spitzer Space Telescope is an orbiting infrared observatory. It ran out of coolant a few years back — needed to keep its highly sensitive IR cameras working — but before it did, it took this amazing image of a young star blasting out twin jets of matter:

Neat! [Click to collimatenate.]

The star is called Herbig Haro 34, and is only a few million years old. Stars that young rotate rapidly, have fierce magnetic fields, and thick disks of material surrounding them (out of which planets might form). All these things together help focus twin beams of matter called jets, which blast away at high velocity from the star’s poles. We see these quite often around young stars.

But the jets blowing off of HH 34 are weird. They aren’t symmetric.

Astronomers figured they should be. Sometimes the jets blow out knots of gas or sputter a little. And when that happens, whatever forces acting on the star and disk should act on both jets at the same time. But that’s not the case for HH 34: the jet on the right does the same thing the jet on the left does, but only after a 4.5 year delay!

Figuring this out at all wasn’t possible until this Spitzer image was taken. Before, visible light images only showed one jet:

On the left is an image from the European Southern Observatory’s Very Large Telescope compared to Spitzer. In the VLT image you can see the jet on the right, but the jet on the left is obscured by thick dust (though you can see the bow shock at the end of the jet as it slams to a halt after plowing through all the gas and dust surrounding the star). Once Spitzer was aimed HH 34′s way, the second jet was viewable — IR can pierce through all that dust — and the timing could be determined. You can watch an amazing animated GIF showing the motion of knots in the visible jet taken by Hubble Space Telescope, too.

So what’s causing the delay? It’s not clear. But, it must have to do with the disk; anything coming from the star itself should happen simultaneously to both jets. Maybe there is some asymmetry in the disk that allows one jet to precede the other. If there is some event happening in the disk, then it must somehow "talk" to both jets, delaying one over the other.

That sort of information propagates through material at the speed of sound. Using the known speed of sound in disk material like that, and the time delay of 4.5 years, astronomers have determined that whatever it is focusing the jets has to be smaller than about 500 million kilometers (300 million miles) in radius — about three times the distance of the Earth to the Sun. If it were much bigger or smaller than that, the delay wouldn’t be the right amount. Before these Spitzer observations, that size was estimated to be more than 10 times larger, so astronomers have been able to greatly narrow down the volume of space in which these jets are generated.

Herbig Haro 34 is about 1400 light years away in the direction of Orion, where lots of other young stars are being formed. The phase in a star’s life when it blows off jets like these is short, so it’s an interesting event to understand. It’s possible, even likely, that 4.5 or so billion years ago, our own Sun looked very much like HH 34 when it was a baby. Given that, and what I know about human babies, it’s hard not to see the analogy of, um, oh how to phrase this delicately? Having material blowing out of both ends.

Imagine having a baby that could do that over several light years! I’ll have to remember that the next time a new parent friend complains about the cost of diapers or burping cloths. It could be a lot worse.

Image credits: Spitzer/VLT: NASA/JPL-Caltech; Hubble animations: NASA/ESA Hubble and Patrick Hartigan

Related posts:

- Baby stars blasting out jets of matter
- C beams off the shoulder of Orion
- Hubble celebrates 20 years in space with a jaw dropper

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (16)

  1. Messier Tidy Upper

    Stunning images. Fascinating star*. Great write-up. :-)

    But a rather unappealing analogy. :-o

    * Or is that proto-star? T-Tauri / Fuor stage? ;-)

  2. Messier Tidy Upper

    Mind you, I do like your alliterative title choice, BA ;-)

    Three questions I’m really curious about if I may ask :

    1) Can someone please enlighten us all as to what spectral class this star is – or will become?Is Herbig Haro 34 a pre-main sequence star? Proto-star? T-Tauri /Fuor / nebular variable?

    2) How massive is Herbig Haro 34 versus the solar mass?

    3) Do we have any more precise idea of HH 34′s exact age other than “a few million” years old?

    IOW, When do we need to send it a birthdy a card & how many candles on its cake!? ;-)


    Phil Plait:

    It’s possible, even likely, that 4.5 or so billion years ago, our own Sun looked very much like HH 34 when it was a baby.

    Aww… oochy-woochy coochy-coo.* ;-)

    *(From Star Trek: TOS — “Friday’s Child”.)

  4. mfumbesi

    Its all my fault really, because I’ve just imagined a baby spouting debris on both ends. I also added the smell and the sounds in my head…..ewww

  5. Ginger Yellow

    That sort of information propagates through material at the speed of sound.

    In space, Spitzer can hear you scream.

  6. Joseph G

    Cool!!! I’ve heard of polar jets coming from black holes, but not young stars.
    Oooh, I can’t wait ’till the James Webb telescope goes up!! Moar infrared goodness and no coolant to run out!

    Incidentally, is it just me, or do most of these infrared images look a bit blurry compared to their optical counterparts? Are far infrared wavelengths long enough to limit the resolution of IR cameras? For that matter, I can’t remember which end of the IR spectrum is “far” and which is “near”.

  7. That small animation is simply the best. Usually when I think about space, I think about A LOT of more or less static stuff. Even though I ‘know’ everything is in motion, you hardly ever see it. But with a short animation like this, it immediately comes to life..

  8. Joseph G

    @8 Emil: I know. it really gives you a sense of scale. Or a sense that scales are so huge that we can’t honestly get a real sense of them :D

    FYI, there’s a more colorful (though much smaller) animation on teh Wiki page for Herbig-Haro Objects.

  9. DrFlimmer

    @ #7 Joseph G

    Jets are a by-product of accretion. So whenever an object consumes matter it produces jets. That’s true for black holes, neutron stars, white dwarfs and young growing stars.

    The blurriness of IR images should be due to the fact that resolution is inversely proportional to the wavelength. “Near” IR is that part that is close to optical (red) light (say about 1 micron) and “far” means that it is, well, far away from the optical band (10 to 100 microns or so).

  10. Joseph G

    @#10: An accretion disc is an accretion disc, eh? :)

    Ah, ok. Anyway, so yes, I did mean far infrared, then.

  11. Rampant speculation: I wonder if the star is bobbing up and down relative to the disk? That would imply a very massive disk, though.


  12. DrFlimmer

    @ #11

    Yeah ;) All you need is an object with enough mass to form a “gravity well” and some matter that intends (or is just forced to) fall onto the object. Since the infall will normally not be radially, it does not hit the object but is forced into an orbit. When there is enough matter to do this it will form a disk in equatorial plane – the accretion disk, which is revolving around the central object.
    In order to get rid off this rotational movement one needs friction and magnetic fields. The latter are eventually taken with the disk, since it will turn into a plasma. Due to the rotation the magnetic field will become twisted and form two narrow channels along the rotational axis of the central object – the jets.

    This is the basic picture, but the details are not yet understood.

  13. Anchor

    This one is truly a puzzle. One might naively think that the (optically visible) jet on the right that has knots that seem to have been squirted out 4.5 years tardy compared to the comparable knots in the opposite (infrared) jet would come about simply from the common effect of light-time arrival of an extended object at some sufficiently large angle to the plane of the sky. In that scenario, recall that extended astronomical objects of some size – say like galaxies seen edge-on – cannot be viewed by an external observer as if it were a ‘snapshot’ of the object at some given point in time. With edge-on galaxies comparable to the Milky way, for example, suppose one sees a supernova event in the far part of the disk and anoither one happening in the near part of the disk in the same month: we don’t often think about our view of the host galaxy in question being ‘spread out in as much as hundred thousand years, or stop to consider that, although we saw two supernovae go off nearly simultaneously from our point of view, that the farside supernova exploded as much as a hundred thousand years BEFORE the nearside supernova exploded from the reference frame of the galaxy itself. By the time the light of those respective supernovae reaches us, we see two supernovae going off within a month of each other, and think they happened nearly simultaneously in that galaxy.

    Similarly, with respect to jet phenomena of any kind, one would naturally expect that a structural symmetry on both sides would reflect the activity of a single central engine: if something big blazes up at the core, one naturally expects bright knots of plasma to be ejected in BOTH jets and that they would travel outward at comparable speeds, covering the same distance in a given amount of time from the reference frame of the central engine. BUT, if the jet axis is tilted with respect to our plane of the sky, and the jets are sufficiently extensive in lenth (say, on the order of light-years or more) one jet will inevitably be closer to a given observer like us than the other is. Thus, unless we are viewing the jets almost exactly broadside, when we measure the apparently angular distance between the central engine and apparently homologous knots on either jet, we should EXPECT to find that there will be a displacement that indicates which jet is pointed toward us and therefore closer than the oppposing jet, and would naturally find that far jet appears to have a pattern of knots measurably closer to the central engine than their counterpart knots in the jet angled toward us and therefore closer to us.

    This scenario is merely a consequence of elementary geometry coupled with the finite velocity of light, and it has been well documented in a wide variety of phenomena, most strikingly – and spectacularly – documented with a series of Hubble images over the course of several years, in the 2002 outburst of V838 Monocerotis which produced a light-echo which perefectly illustrated the effect of signals being delayed from reflecting material (cirumstellar dust clouds) that is farther away compared to those signals reflected by material closer to us observers. We could actually WATCH how light reflected from stuff BEHIND the star arrived much later than light reflected off of stuff closer to us along the direct line of sight. But its vital to remember that the light echo played out over several years after the SINGLE outburst occurred: a classic case of a very brief flash of an event spread out in time because of the extension of the size of an object in terms of distance (the circumstellar dust clouds that reflected the light of the brief outburst).

    It doesn’t take into account any relativistic effects which may also play a dominating role (as has frequently in fact been observed with certain quasar jets and the famous jet emmanating from the core of the Virgo galaxy cluster giant elliptical galaxy M 87), which complicates the timing issue of jets aimed nearly in our direction even more.

    Given all these potential issues, the case of HH 34 is nevertheless puzzling. It does not seem to follow the simple rules I’ve outlined above. For example, it is difficult to reconclie a 4.5 year delay on one jet with respect to the other when the entire jet structure might be at most 10 to 20 light-years in extent. Moreover, its hard to understand how the optically exposed jet on the right would exhibit the LAGGING, unless it was pointed drastically AWAY from our direction compared to the opposing and optically hidden jet. There’s definitely something screwy about the asymmetry that doesn’t immediately suggest an accounting. I can’t buy the ‘sound-wave’ mechanism as an explanation yet; it seems too contrived and I can’t reconcile it with the apparent coherence exhibited on both jets over most of their extended lengths. Rather, I think, as usual, the answer will probably turn out to be a far more simple one, and one that points out some currently unnoticed observational error of some kind (even though the measured displacements are real – I measured them myself). Whatever the explanation ultimately turns out to be, encountering an authentic natural mystery is always welcome and infinitely more rewarding than messing around with the fake superstitious kind, which aren’t mysteries at all.

  14. Interesting, BA. Such a young star, and some good images of its infantile temper-tantrums as well. It will be fascinating when it’s discovered why the jets are behaving the way they are. Gods of Howard Phillips Lovecraft…Science is cool. Thanks for posting on this.


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