Hi.
My name is Dr. Phil Appleton at Ipac, Caltech.
And I want to talk to you about some new images.
So the image of Stephan's quintet that was just released by the James Webb Space Telescope.
I've been working on this system for about 18 years.
So we started first with the Spitzer Space Telescope, which is in some ways the forerunner
of the JWT, a very powerful telescope in its own way.
Okay.
So what we're seeing here, it's a composite of different colors that represent the different
bands that are observed.
And the most important thing that you see in the image are these diffuse objects which
are galaxies.
And this is called a compact group of galaxies.
And you have a very big one here, and then there are two here and another one down here.
And this is the fifth one, and that's why it's called Stephan's quintet.
When the quintet was first discovered at the end of the 1900s by a guy called Stephane,
it was not known that these systems were like giant, that these blobs, essentially, that
he saw in his images were entire Milky Way systems.
And what's fascinating about Stephan's quintet is that all these galaxies are crunched together
in a very small area of space.
Do you imagine our own Milky Way system, which is a giant pinwheel of rotating gas and dust?
The nearest galaxy to us is the Andromeda Galaxy, which is a faint folds in our own
sky when we look
up there.
But the Stephan's quintet, which if you imagine this is our own Milky Way system, these galaxies
are very, very close, within almost 1/10 of the distance between our own Milky Way and
the Andromeda.
So these galaxies are very, very close together.
And as a result of that, they tend to be smashing into each other and colliding and producing
what we call tides.
I mean, just like you have tides on the earth, it's that in galaxies, tides cause these long
tails to be produced when galaxies pass by each other very closely.
And this is a beautiful example of that.
You can see this long tail here, and this is a tail of stars that are being strung out
on gas caused by this due to this galaxy colliding with one of these in the past.
We don't know exactly which one.
What's interesting about this is there is another galaxy here which is not part really
of the physical association of these galaxies.
This one is much, much closer to us.
These are far, far away in comparison with this one.
But I'd like to show you now another image that was taken in the past.
So this is an image of the same region.
And this time it was taken with Hubble, the Hubble Space Telescope, in the visible, visible
light and the background image.
Here, you can see the same galaxies.
And here's the foreground object is the galaxy that had the long title tail and superimposed
on this picture, which is mainly showing you stars and a little bit of dust, is an observation
that was made by my team on using the Spitzer Space Telescope, and it was able to detect
this
structure across the center of the system.
And what is the nature of the structure?
We believe that these are molecules of gas or molecular hydrogen that are emitting infrared
radiation.
And so Spitzer was able to see the infrared radiation.
And in the background, you see the stellar emission from mainly from stars.
And what this told us is something very strange going on here.
And what we believe is happening is that this galaxy here is actually flying into the group.
It's colliding at a tremendously high velocity, smashing into the gas that surrounds the galaxies
and is producing an enormous shockwave in front of this galaxy.
And the shockwave is producing little clumps of stars along the shock front.
And what if I go back now to the the j wac t image?
What's amazing about this now is that we can actually observe the molecules in great detail
and that's what we're seeing along here.
And if we zoom in on this, you can see all these molecular structures along this shock
front.
When those clouds are compressed, they they they collect.
And in fact, it's a sort of battle between the shock wave, which is driving energy into
the gas and then the gases ability to collapse to form stars.
And in fact, star clusters are appearing also in here along the shock front.
And here's another image from GW of ASG where we can zoom in again on that same region.
But now we're seeing purely stars and in particular, infrared emitting stars.
So these are stars, star clusters, that are usually very young.
And you can see up here, for example, there's lots of little speckles and things that are
basically the result of of the beginnings of star formation, where stars are hidden
inside their little dust clouds and they are starting to emerge from the dust clouds and
form stars.
So there's a battle going on between the energy pumped in to the gas from the shockwave and
the gravity which is trying to form stars.
And so we've got this tremendous battle going on along here.
And that's what makes it interesting to us, because we're trying to understand how stars
form in very turbulent environments, which is what
we're seeing here.
One critical question that astronomers have always tried to understand is why star formation
is quite inefficient.
Why?
Why is it that there's lots of gas in the universe, but the star formation that occurs
in the universe is is is very inefficient.
And so by understanding this system here, we can understand the physics of the astrophysics,
of how the stars are being born in a highly disturbed and turbulent and stirred up environment.
And then we can apply those kinds of ideas to looking at the early universe, where we
think that such things, you know, galaxies collapse out of gas
. Shockwaves and turbulence are definitely a major factor in in the formation of galaxies.
So it helps us understand how galaxies formed in the first place.
And we're using this as a sort of local sort of testbed to try to understand the basic
underlying physics of it.