Text Version

SALT: Imaging the Southern Sky 

Video transcript
The video is 8 minutes and 2 seconds long.
Produced by the American Museum of Natural History, October 2008. 
Video begins here.
Visual: Dawn in southern Africa. Daylight hits a scientific facility in the desert. A telescope sits in the facility. 
Speaker: Patricia Anne Whitelock, South African Astronomical Observatory, Professor, University of Cape Town 
Telescopes are really very simple things. They collect light. 
Visual: Patricia Anne Whitelock. 
Telescopes are really very simple things. They collect light. They work in a way a bit like the human eye. And you can imagine a telescope as a giant eye. 
Visual: The telescope, as seen from above.
The bigger the telescope, the more light it can collect, and the further it can see. And it really is just as simple as that. 
Visual: The numerous telescopes of the South African Astrononomical Observatory sit on an African plain.
So if you could build a very big telescope, you can see very faint sources, and you can see very distant sources. Sources at the very edge of the Universe. Things from which the light has taken over 12 billion years to get to us.
Visual: Title: S.A.L.T.: Imaging the Southern Sky
Visual: The S.A.L.T. logo. The S.A.L.T. facility. 
S.A.L.T. is the Southern African Large Telescope. It’s the biggest single optical infrared telescope in the Southern Hemisphere. 
Visual: Patricia Anne Whitelock
And I think what’s so important about the project is that it is an international collaboration. 
Visual: A map of Earth with collaborating institutions indicated; UW-Madison, HET, CMU, Dartmouth, AMNH, Rutgers, UNC, UKSC, Poland, Gottingen, SALT, ICUAA, Canterbury. 
It allows us to work with people from the United States, from Europe, from India. 
Visual: The map curves in onto itself into a globe, and is seen from outer space.
And to bring those resources together to study the exciting things you can only see from the Southern Hemisphere. 
Speaker: Thebe Medupe 
Visual: Wild animals graze in front of the SALT telescope. 
For people like me, who love our continent, S.A.L.T. could be a focal point for development of scientific research in the continent, the African continent. 
Visual: Thebe Medupe, Senior Research Fellow, South African Astronomical Observatory
Because we have this fantastic first-world, first-class facility that can attract astronomers and people who want to do astronomy in the whole African continent or just in south Africa. 
Visual: A road sign pointing to SAAO. A building sign reads, "Sutherland Observatorium Observatory". 
S.A.L.T. is built in Sutherland. 
Visual: The telescopes of the Sutherland Observatory.
And the location was chosen because there was already another observatory existing there. Therefore, there was also infrastructure there. I mean, you didn’t have to go and start building an observatory from scratch.
Visual: The observatory dome opens to reveal the night sky. David Buckley issues instructions over a hand-held radio at the base of the telescope. 
Speaker: David Buckley 
OK, home in back again to 240, please. 
Speaker: Man on radio.
Nicola, we’ll move to 240. 
Visual: The telescope rotates to the given orientation. 
Speaker: David Buckley 
This is the heart of the telescope. 
Visual: David Buckley stands at the base of the telescope, pointint out its features.
The primary mirror array, which consists of 91 individual mirror segments in a spherical configuration. 
Visual: The 91 hexagonal mirrors of the SALT telescope.
This is equivalent to a mirror that would be eleven meters by ten meters in size. 
Visual: David Buckley stands at the top of the mirror array, motioning to describe its size.
Building something eleven meters in size is just, at the moment, technically impossible. 
Visual: A grid of identical images of David Buckley speaking.
So instead, we’ve made it up from a mosaic of individual segments that collect the light, and focus it up to the instrument at the top of the telescope. 
Visual: The collecting instrument into which SALTs mirrors focus their light. 
Visual: David Buckley, SALT Project Scientist / Astronomy operations manager, South African Astronomical Observatory
At the moment, we have two science instruments on the telescope. 
Visual: SALT's imaging camera.
One of them is an imaging camera. 
Visual: A grid of artist's renderings of an eclipsing binary star.
Very similar to a video camera, which is used to make observations of varying phenomena, where the light is varying for one reason or another, possibly on quite short time scales. So this camera can take up to ten frames a second. 
Visual: An animation of one of the stars revolving around the other.
And so for things that are rapidly varying, that’s an ideal sort of instrument. 
Visual: The spectrograph of the binary star system. Hydrogen is indicated in two places, and velocity is indicated along the horizontal axis of the spectrograph. 
The other instrument is a spectrograph, which splits up the light into component colors and then analyzes what we call the “spectra” of an object. And so, with that instrument, you’re able to probe a lot of detail, and get a lot of physics out by looking at galaxies and stars and so on. 
Visual: The SALT observatory at night.
In any given night, we will be observing many different objects from many different programs, which is quite different to the normal, classical way of scheduling telescopes, where an astronomer might get a telescope to themselves for one or two nights. 
Visual: An astronomer. 
Speaker: An astronomer.
OK, that should bring it to focus. 
Speaker: Petri Vaisanen
Visual: Petri Vaisanen examines information on various computer monitors. 
All right, track time, hour-and-a-half. Going straight through the central supply rate, that's good.
Visual: Petri Vaisanen continues working at the computer.
All right, S.A.L.T.-i-cam is back on track. 
Visual: Petri Vaisanen uses a mouse to input information into a complex control system.
Say, half an hour from now, extending 45 minutes from that time on. I query the database, and it gives me several programs which are visible at that time. 
Visual: The database Petri Vaisanen is consulting.
In this case, it’s only two targets. One is looking at galaxies from our Israeli collaborators. And there’s another target looking for Kuiper Belt objects. These are small bodies, celestial bodies on the outskirts of the solar system. 
Visual: An animation of stellar objects seen by SALT.
So we use S.A.L.T. for science from, in astronomy, basically from one end to the other. We can look to the very, very distant Universe, and we can look at stars in our own galaxy. 
Visual: Petri Vaisanen
But then there are programs also which look at objects inside our own Solar System. 
Visual: Petri Vaisanen brings up a stop-motion video of asteroids on his laptop. 
Here’s an example of an observation we made recently, of asteroids. These were ten-second exposures. 
Visual: Petri Vaisanen points out an asteroid moving across the star field with his finger.
See the asteroid moving over here. So every frame is one S.A.L.T.-i-cam frame from the telescope. And we just put it together, and you see the object moving over there. 
Speaker: David Buckley
Visual: David Buckley 
There’s been a lot of science which has hinged around having this camera, that could take very, very fast observations. 
Visual: The SALT Telescope
And then with the spectrograph, we were able to do quite a lot of very interesting observations of some colliding galaxies. 
Speaker: Petri Vaisanen
Visual: Petri Vaisanen
One bit of research which we just recently finished was a galaxy we’ve been calling, the “bird galaxy”, because it looks like one. 
Visual: The Bird Galaxy
There was a surprise that the whole thing was supposed to be only two galaxies. 
Visual: A close up of the head portion of the Bird Galaxy.
But for the first time, really resolved, this, what we call the head of the bird, it really is a galaxy of its own. 
Visual: The blue wing sections of the Bird Galaxy.
Everything which is blue over here, is new stars being born. 
Visual: A close-up of the central, red section of the Bird Galaxy.
And on the other hand, the red bits are very obscured regions. There’s a lot of dust inside. 
Visual: Petri Vaisanen's laptop displays an image of the Bird Galaxy and its emission lines. 
So with S.A.L.T., what we did, we got a spectrum, the bright things are actually emission lines.
Visual: Petri Vaisanen points out the elements indicated by the emission lines.
This is actually hydrogen. And these two are nitrogen lines. And further on, you see sulfur. 
Visual: Petri Vaisanen, at his desk, continues explaining the various elements present in the Bird Galaxy.
And then was sodium, and oxygen, and all those. 
Visual: Petri Vaisanen points out more details of the Bird Galaxy's emission lines.
They are twisted. 
Visual: Petri Vaisanen continues to motion to the various parts of the emission lines.
Means that their velocities are different. 
Visual: Petri Vaisanen motions in the direction of the incoming emissions. 
So this part of the spectrum is actually moving away from us. And this part of the spectrum, well, it’s coming towards us. 
Visual: Petri Vaisanen switches back to the image of the Bird Galaxy.
So when you map now this structure, on the image what we have, you can build an understanding of how this thing is moving. 
Visual: The SALT telescope at night.
Speaker: Patricia Anne Whitelock 
The Universe is a very dynamic place. Everything is moving with respect to everything else. 
Visual: The inside of the SALT telescope, opened and looking out into the night.
And it’s very useful to have a tool to measure that movement. 
Visual: David Buckley
Speaker: David Buckley
As an astronomer, it’s fantastic. 
Visual: David Buckley walks around the rotating SALT telescope assembly.
Because I have now access to one of the largest telescopes in the world. 
Visual: David Buckley examines SALT images and data on a laptop.
So the type of science that I can do is just so much increased. 
Visual: On a laptop screen, the SALT Event Logger, describing the orientation information of the telescope.
It’s just so many possibilities. 
Speaker: Thebe Medupe
Visual: Astronomers monitor SALT data at computers.
Visual: Thebe Medupe
S.A.L.T. is a focal point for development of science, research, and technology in south Africa.
Visual: A schoolteacher writes on a blackboard in her classroom.
With S.A.L.T., we can motivate young people to want to take up careers in science. 
Visual: Students in the classroom weigh objects on a scale.
And with S.A.L.T., we will be able to come up with exciting discoveries that, you know, they give people a good feeling. 
Visual: Students attend to their books, and write notes.
You know, when you know that there’s some good things happening in your country. 
Video ends here.
© The American Museum of Natural History