BRIAN: So Paul, these neutron star binaries are pretty wild.
They have huge amounts of energy.
It seemed to me to have a huge amount of potential
to fill the sky with interesting objects.
You got any ideas of what you think are maybe
the most interesting objects in the sky?
PAUL: Well, I think possibly the weirdest of this whole category
would have to be SS 433, which was like a compete bombshell
to the astronomical community when it was covered back in the 1970s.
BRIAN: It's got a good name too, sounds important.
PAUL: Yes.
And normally, if you look at the spectrum
of one of these x-ray binaries, you'd expect
to see a particular emission line-- say, h alpha-- from the gas around the disk.
Now, this particular object, SS 433, was observed here in Australia
at the Anglo-Australian Observatory.
And it was an x-ray source and a faint radio source.
And it seemed to have a sort of nebula around it
that might have been the remains of a blast wave of something.
So it was an interesting target.
And when they looked at this, they got a spectrum.
And sure enough, it had the big line there-- but also, the line over here.
BRIAN: Ooh.
PAUL: And another one hiding behind you.
BRIAN: And over here too.
PAUL: But they didn't see that one.
The original data only covered this range,
because the spectrograph's weren't too good back then.
And this caused a lot of puzzlement, because they'd look up-- OK, line here.
And what you normally do is you look at a line,
and you look up the list of elements and see
which one showed up at that wavelength.
But there wasn't any really obvious plausible element
that showed up at that wavelength.
BRIAN: Hm.
PAUL: So what's going on?
Some mystery Kryptonite or something like this?
A new, weird element?
BRIAN: New element, but in a good way.
Astronomers think of the universe as being the world's greatest laboratory.
So maybe it's a new element.
PAUL: But well, they went to re-observe it a bit later, and they're gone.
BRIAN: OK, so--
PAUL: So what do you think when that happens?
Do you think you've already stuffed up your spectrum somehow?
BRIAN: Well, when I see something really weird,
I just assume there was a little glitch.
A cosmic ray came in and wasn't right, yeah.
PAUL: OK, so they thought maybe it was a bit funny,
but maybe you shouldn't publish that maybe.
BRIAN: Yep.
PAUL: So avoiding, sweeping under the carpet a little bit.
However, when more observations were made-- this time
in California-- people discovered that first of all,
there were two of these things.
But also, they came and went.
They came back.
And they moved around, so it actually moved backwards and forwards
in wavelength in a symmetrical way.
So you see, they'd go both in closer towards the line,
and both further away from it.
Now, what could cause that?
BRIAN: Well, my sense is it's probably not
a bunch of new elements being synthesized.
But it strikes me as something that seems related to the Doppler shift
somehow.
PAUL: Yeah, I mean, an element can't move around.
It's going at the same wavelength.
So this is presumably something that's moving.
And given there are two of them roughly symmetric-- they're not exactly
on either side of this-- maybe it's this line,
but there's some gas coming out from this thing moving towards us
and going away from us.
BRIAN: So what's the implied velocity of the gas?
PAUL: Well, these are a long way separated.
We're talking at more than 20% of the speed of light to make this happen.
BRIAN: 20% of the speed of light?
PAUL: Yes.
BRIAN: Wow, OK.
So that's a lot.
That's a pretty amazing velocity indicated.
But the amazing thing, is, of course, we have a neutron star here, so almost
a black hole.
So you really can't imagine getting things up
to that type of speed potentially.
PAUL: Yeah, but that was-- you'd think there would be stuff falling.
And maybe there's stuff falling in from one side
and falling in from the other side.
And so this stuff that's blue shift to it is on the far side falling in.
And that stuff that's red shift is on the near side going in.
But when they actually observed this thing
with modern radio telescopes, what you see is something like this.
It's a corkscrew.
Now, you're the expert on corkscrews here, Brian.
BRIAN: Ah, yes, although mine tend to be used
for extracting things, not just playing around in space.
So let's see.
We have literally this amazing corkscrew in both directions.
Now, that's sort of sounds like a jet, but a jet which is being precessed,
I can't-- I'm not coordinated enough to do both arms.
But if I do that with a fire hose, which I do sometimes on a hot day,
I'll get a corkscrew out.
And if the fire hoses are stuck out, then they'll
kind of go like that, like a kayaker.
And you'll get exactly that thing.
But it's a jet moving at 20% of the speed of light.
PAUL: Yes, and we know-- the first course, we talked about quasars
and how they had these jets squirting out.
This is not a quasar.
It's a neutron star binary in our own galaxy.
But it seems to have the same sort of thing--
two jets being squirted out opposite directions.
But as you say, they are precessing.
They're moving around something like this.
And that's a bit weird.
So what's going on here?
I guess the idea would be that this is normal,
a star that's donating mass which is forming an accretion disc
and swelling down to the neutron star in the middle.
But somehow, as gas comes in, some of it goes out at this enormous speed.
And this is a bit weird.
I mean, why should be stuff falling in produce stuff going out?
It's, in fact, embarrassing that we actually
never observe stuff falling into these things.
We only infer it indirectly.
But all we ever see is stuff coming out.
But we know this is common whenever we have a disk.
So for example, a protoplanetary disk, because it
was covered in the first course.
We get jets coming out from this.
We've got bipolar outflows.
We know that quasars get a disk around a black hole, and that produces a jet.
So It seems to be generically true that you get jets quite often.
But why are you getting a jet in this one
and not all the other X-ray binaries?
BRIAN: Well, it's not obvious to me why you would get it.
But it is interesting that if you have a big mass here and this thing,
it might precess around like a giant top.
The earth precesses around every 26,000 years.
PAUL: Because of the moon pulling on it.
BRIAN: Yeah, the moon and the sun interaction.
So it's not completely crazy.
But that whole process of how to create a jet from in-falling material
is one of those sort of mysteries of the universe still.
PAUL: It probably has something to do with magnetic fields.
Whenever we don't know what's going on, we invoke magnetic fields.
BRIAN: That's right.
Now interestingly enough, Paul, with our SkyMapper telescope,
we were out looking around for objects-- in our case,
some of the first, oldest stars in the universe.
And we look at them by finding things that are very funny colors.
And we found an object that sort of looks like this.
It's not exactly the same.
But we found something that seems to be having jets
shooting out at a large speed in a way analogous to this.
But it's in a very funny location.
It's not towards where young stars are in the galaxy.
It's kind of off a long ways away from the galaxy.
So it's maybe a sort of a dead version of this,
like a really old version of this or something.
We're not sure.
We still need to get more data.
But it's one of the exciting things that you can find.
There's really nothing else like it that anyone's ever discovered before.
PAUL: OK, so maybe SS 433 is not alone in the universe.
