So, Paul, I'm really excited about this. So, what have we learned?
Well, lots. A number of these things have now been seen. Here's one of the early ones.
This is a star and you can see that here's the data from OGLE that the star didn't change in brightness for a very long time, about 1000 days.
It was a very boring star. Then suddenly, around mid July 2005, you see that it started inching up in brightness.
Right, okay and so it started getting a little bit brighter and so they would have been able to send the alerts, presumably.
Yes, and then it started really climbing around here, it got a bit less data, I assume it was cloudy or something around there,
but by this point it's climbing quite fast and they were able to fit the microlensing curve and realise what they were looking at.
At this point a warning went out and people around the world started following up.
So, for example, telescopes in Australia, in Perth, the Danish telescope in Chile, MOA in New Zealand
and as the world rotated these three telescopes would come online.
You see this happening over several days, so it got brighter and brighter and brighter, peaked at about magnification of three.
So, presumably, as you watch this coming up, it looks like it's just a big magnification event and just a star.
So, just a star, just a star, just a star, just a star, just a star... Ooh! What happened there?
Ooh, there's a little glitch in it, yes.
If you zoom in on that, you can see that these glitches are a long way outside the arrow bars,
so what's a very small glitch is very real and that's exactly what we're expecting. We're expecting a big star pattern with a glitch on the side.
Right, and so the fact that that glitch is really narrow tells you that it's something that's not that massive.
Yes, in this case it's a caustic, you've crossed a caustic here most likely, so caustics are very narrow.
You can see that this is only going over a few hours, this narrow spike,
and so without the whole network of telescopes around the world, we wouldn't be able to follow this up.
So, their analysis of this, and because we have a fair bit of information here,
they were actually able to be the first group using this very tricky technique to find something that looks like a Super-Earth,
that is, a planet that is bigger than the Earth but smaller than a Neptune.
Yes, so this is the first one, because this came before all of the results from Kepler and the transits. We're talking 5.5 Earth masses.
The arrow bars are asymmetric, so there's a big uncertainty in the upward direction
and a smaller uncertainty in the downward direction, so it could be twice that.
It could be 11 or it could be half that down to maybe two Earth masses,
but anyway it could be just about as big as Neptune or something like that.
So, we don't know if this is a gas giant or a rocky planet.
Yes, once again, all we know is the mass. (So, we know the gravity and that's it.)
So, the Super-Earth, you've seen lots of Super-Earths before, but the interesting things is this one is a long way out.
All of the Super-Earths that have been found by Kepler, they're all very close in with orbital periods of within 50 days.
This one is 2.6 astronomical units out. That's a little bit like where Mars is in our own solar system near the astroid belt.
Okay, so this is getting to being something that looks and smells a bit more interesting with the respect to our own solar system.
So, it looks like Super-Earths are not only close in, but they're also further out
and we're for the first time been able to see planets out at a decent distance.
Is this the only one we've seen?
No, there are more. Let's show you some examples. Here's a rather more complicated one.
They got data from both OGLE and MOA, the two surveys.
Here's the old data ones showing that it didn't do anything, didn't do anything, didn't do anything...
until suddenly it started climbing, likewise, OGLE found the same. Didn't write that trigger.
MOA found the same, so here's their data, nothing, nothing, nothing, nothing, spikes.
Doesn't look like there's much follow-up data here, so it's probably just their own data from the surveys on these ones.
So, they weren't able to sound the alarm in this case, obviously, or maybe the surveys weren't in place yet.
But, nonetheless, it looks like something's happened.
The model says there's a big glitch here, it didn't actually manage to zoom in on that. Let's zoom in a bit.
So, certainly it was climbing here. It would have been nice to get an observation right up there
but it'll probably be just a gap between two exposures or a cloud went over or something.
We went down again, this time, the seconds spike, they actually managed to get an observation from the top.
They nailed it, yes.
They also nailed the shape around here.
So, it's a very complicated shape which means that you could learn a lot about the system.
Yes, and in addition to these two big variations, there are a couple of small ones off elsewhere that you can hardly see,
and combining these all you've got multiple caustic crossings
and in this case it turns out that you've got a 1.5 Jupiter mass object about three astronomical units out.
So, that is something that's very similar to Jupiter, it's not quite as far out as Jupiter.
A bit bigger and not quite as far out but beginning to look like a...
But it's going to be the closest thing we have to Jupiter,at least, I mean, this was in 2004.
Yes, now it's not always that obvious. Here's another example of a microlensing event,
and that pretty much looks like there's just a star if you eyeball it like this.
This is a very quick thing, looking at only a few hours across here, you can see that it was being observed by telescopes in New Zealand,
that it was picked out by an amateur astronomer in South Africa and followed it through the maximum,
then down here it started getting picked up by telescopes in Chile as the Earth rotated.
But the South African got lots and lots of data very quick, very accurate things.
If you try and fit a model for a single star lensing event to this, you see it doesn't quite fit.
There are a few little wiggles around it.
So, these are tiny little wiggles in this case, which means that the thing probably just wasn't lined up.
It didn't really didn't go through a caustic as much as other things.
Well, it turns out in this case, most likely the reason why the wiggles are small is what's called 'finite source problems'.
Here's a model fit to the data and you can see that you can fit the wiggles,
this is actually a hard thing to fit, but you can actually can fit it all very well.
The idea is that here's the image plane and here are caustics, these green and blue lines through different models.
Everything you're doing so far has been assuming that the background source is a point,
but in fact the background source is a star, which is a finite diameter which is comparable size to the caustics in this case.
So, say this part of the star, as it drifts across, will be lensed quite a lot because it'll go over a caustic that part wont be very much.
Okay, so a tiny little piece of that star is magnified.
Yes, so because in this case the star is comparable in size to the caustics,
bits of the star are being magnified, bits are not and you have to allow for that.
But if you allow for it, you see a pretty good fit.
Since most of that data is from an amateur, it really goes to show
that amateurs with modern equipment can really be at the cutting edge of astronomy right now.
Yes, and in this case, we've got something a little smaller than Saturn which is 1.25 astronomical units out.
So, something like Saturn at the approximate place of Earth.
This could be one of the elliptical giants that we talked about.
This is actually a similar thing to what's been found by some of the radial velocity searchers.
Okay, so we're sort of finding where we can find overlaps, we are finding some overlaps, that's good.
We're finding some new ones. Now, lots of people were involved in this. This is an author list of one paper.
It almost looks like something from the Large Hadron Collider.
Yes, so huge numbers of people from around the world doing all this sort of stuff.
Here's the result we get in this particular case. This is a really neat one because there's a lot going on here.
You see lots of different observing situations, so there's a little glitch over here which is only caught by one or two observations.
Then up here, this is not a symmetrical curve, it sort of tilts a bit over there,
then spikes, drops, comes back up again, comes back down and has another spike over here.
It's a really complicated pattern and comparable to lots of caustics here and big caustics.
Normally I would think, when I see something like this, it's a train wreck, it's hopeless,
but because we understand the physics of gravity and gravitational lensing so exquisitely well,
we can fit every little piece of this puzzle in something that makes sense.
Yes, and as it says down here, we've got a Jupiter mass planet, it's about 2.3 astronomical units out,
and a Saturn mass planet about 4.5 astronomical units out.
So, that's really beginning to look like our own solar system, just a little more compact.
But the star is only half the mass of the sun and therefore much less luminous than the sun,
so in fact, in regard to the snow line and the habitable zone, it's actually almost an exact analogue to our own solar system.
Well, that's really exciting.
Yes, so we see a lot of neat stuff with this technique.