The Physics Police

The Physics Police

Wednesday, February 19, 2014

The Lighthouse Nebula

Today I read an ABC Science article by Stuart Gary titled Runaway pulsar has astronomers scratching their heads which starts off:
A newly discovered fast-moving pulsar streaking across the galaxy with enormous x-ray jets, defies the laws of physics, according to scientists.
There are two red flags here.

First, things don't defy the laws of physics. Something can defy explanation within some particular model or theory. When this is the case, a journalist should just say which observation defied explanation by which model or theory!

Second, there is no such group as scientists to which things can accord. When reporting on a published paper, a journalist should name at least the lead author and include the title of the paper as a link to the paper. Here's how it's done:

The paper in question is titled The long helical jet of the Lighthouse nebula, IGR J11014-6103 by Lucia Pavan et al.

I've found that tantalizing and vague language doesn't earn the reader's trust or attention. It only serves to alienate readers who would take the article seriously. I think that should include just about all of them! Why would anyone bother reading the science section unless they are ready to take it seriously?

Red flags aside, the statement is also false. This pulsar, known as the Lighthouse Nebula (designated IGR J11014-6103) was discovered back in 2011! It's no more newly discovered than the first Thor movie. Oh, and in the article, its name was mistyped the star's designation! (UPDATE: I sent a letter to the editor and they promptly fixed this typo.)

Anyway, the article goes on to quote Miroslav Filipovic, coauthor on the 2011 and 2014 papers:
One of the biggest mysteries is that we only see these jets in x-rays, there's no radio signature, that's totally shocking to us ... this is extremely difficult to explain through any theories we have at the moment.
Okay, two things.

First, there most certainly is a radio signature, that's what the whole paper is about!

Left panel shows the Lighthouse Nebula's X-ray signature.
Right panel shows the Lighthouse Nebula's radio signature.
It's right there. In the paper. The paper you published. Come on bro! I can't imagine how this quote came about. It doesn't seem out of context or anything. Maybe Filipovic was referring to the 2011 paper? But no, that paper's abstract says quite clearly:
A possible radio counterpart positionally coincident with the source was also identified.
That doesn't sound like "no radio signature" to me. If the quote isn't taken out of context, or entirely fabricated, then Filipovic might have been showboating. Either way, someone is being dishonest.

Second, the data are not at all difficult to explain. That's the whole point of the paper! You see, a 2012 paper proposed that this pulsar was propelled to a high velocity by its neighbor that went supernova. What's new in this 2014 paper is fitting both X-ray and radio data to a model of the pulsar's spin and velocity.

The radio and X-ray profiles peak at different positions.
This can be explained by the cooling of the emitting particles.
Alignment favors a pulsar high velocity greater than 1,000 km/s.
There's no unexplained, shocking mystery at all! The data easily fit a model where the pulsar is flying away from its companion at high velocity. Not only that, but the spin axis of the pulsar is perpendicular to the direction it's moving.

Think of the jets like the smoke coming from a train's smoke stack. It's really hot when it first shoots out, then expands and cools, forming a slowly fading tail as its source zips on ahead.

This is a great paper. It shows how subtle clues can reveal the nature of an incredibly distant object. You don't have to see the pulsar in detail to know which direction its jets are facing, or how fast it's moving. Science rules!

But this spectacular deductive reasoning is utterly lost to readers of the news article. It's a tragedy of incompetence. Sure, readers get a puff of mystery that alights their human urge to discover. But they won't be given the satisfaction of actual discovery.

Even after reading all three papers, I feel similarly unsatisfied by a question that keeps coming back to me. Why does this news article go out of its way to make Filipovic sound oblivious to the paper's very thesis?

This question really has me scratching my head.

UPDATE: As you can read in the comments below, Miroslav has kindly explained to me that the first picture above is actually the pulsar wind nebula, not one of the the pulsar jets. The pulsar wind nebula is a standing shock wave of charged particles accelerated by the magnetic field, but is an independent feature from the pair of jets. This wind shows up clearly in the radio spectrum. More importantly, Miroslav was correct that there's no radio source of the jets, themselves! My bad.

Though I'm yet to be convinced that a missing jet radio signal is truly unexpected, since the paper seems to indicate otherwise. Also, this quote from the ABC article seems to conflate the radio signal from the jets with any signal from the pulsar itself:
Pulsars were first discovered because of their characteristic radio signals, so this is extremely difficult to explain through any theories we have at the moment.
These quotes have me scratching my head, too:
It's impossible to easily explain all these crazy things we've seen in this object.
Not according to the paper!
One of the problems is, it's impossible to prove any of these ideas.
Not something you do in science!


  1. Dear,

    1. There is NO radio detection of the JETS and that is unexpected!! What you are showing here is radio detection of the PWN -- also SNR is radio detected. Perhaps, this should be better emphasised!
    2. While we do have possible explanation about the whole "system" (SNR-PWN-Pulsar-JETS) there are other number of possibilities that could explain various specifics of each of these "elements".
    3. expressions such as "defy the laws of physics" are certainly bit strong and one should be very careful when use. In this particular case UNEXPECTED and/ or "not seen before" would be more appropriate.
    4. The link to the original paper and the names of authors should be should be acknowledged as they are in the original NASA/UWS PR.

    Best regards,

  2. Miroslav,

    Thanks for your comment!

    1. I didn't even realize the pulsar wind nebula (PWN) is independent of the jets. The first image I posted, of Figure 3, doesn't even show the jets! I will edit this post so this distinction is clear. However, when talking about the companion star on page 6, the paper says:

    "The neutron star and jet structures are not detected in radio, which is a common feature amongst many high-energy emitting pulsars and pulsar jets."

    If these jets absence in radio is so unexpected, why isn't this noted in the paper? Can you share with me a paper predicting supersonic pulsar jet radio intensity?

    2. Right, but that isn't at all the tone of the ABC article.

    3. Agreed.

    4. Oh, can you share a link to the original NASA/UWS press release? I was unable to find it.

  3. Dear PhysicsPolice,

    1. Thanks for the corrections. I would like to ask you that we continue this discussion (on the (non)expectation of radio jets) offline. The reason is that we are working a new study (paper) that may further shed lights on this certainly unusual system. There are several other groups working on this object (right now) and I don't want to jeopardise some of our latest findings. I am sure that you will understand! However, I am happy to share and discuss this with you in private.

    2. This is also something that I would prefer to further discuss with you in private.

    Could I also ask you to consider withdrawing your last paragraph of your original blog.


  4. Miroslav,

    In a conversation about science, "it's a secret" makes a very poor argument.

    Thanks for the links to those press releases!

    Fair enough. I edited that paragraph to more clearly express my frustration towards the article. I think the update makes sufficiently clear my frustration with your showboating.

    I look forward to reading your next publication,

    - Physics Police