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Dr Brian Schmidt was interviewed in 2001 for the Interviews with Australian scientists series. By viewing the interviews in this series, or reading the transcripts and extracts, your students can begin to appreciate Australia's contribution to the growth of scientific knowledge.
The following summary of Schmidt's career sets the context for the extract chosen for these teachers notes. The extract covers projects he works on at Mount Stromlo. Use the focus questions that accompany the extract to promote discussion among your students.
Brian Schmidt was born in 1967 in Montana, USA. In 1989 he received a BSc in physics and a BSc in astronomy from the University of Arizona. He went to Harvard University for graduate work and received a PhD in astronomy in 1993. His thesis research was into Type II supernovae, expanding photospheres and extragalactic distance.
From 1993-94 Schmidt was a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics. In 1995 he began work at the Mount Stromlo and Siding Spring Observatories (MSSSO) as a postdoctoral fellow. He has continued working there, being appointed in 1997 as a research fellow (MSSSO) and in 1999 as a fellow in the Research School of Astronomy and Astrophysics (MSSSO) of the Australian National University. His research interests and current projects include observational cosmology, studies of supernovae, gamma ray bursts and transient object searches.
Schmidt is the leader of the High-Z-SN Search team, a collaboration of 20 astronomers on five continents whose discovery of an accelerating universe was awarded Science Magazine's Breakthrough of the Year award in 1998. He is also a member other international investigative teams, including the Supernova Intensive Survey and the REACT Gamma Ray Burst Follow Up, both with the Hubble Space Telescope, and the Trans-Neptunian Object Search with the Mount Stromlo GMT telescope.
Among the numerous awards and distinctions to be received by Schmidt are the Australian Academy of Science's Pawsey Medal (2001), the Australian government's Malcolm McIntosh Prize (2000) and the Harvard University Bok Prize for Outstanding Astronomical Thesis (2000).
Why is the sky growing so fast?
So what are you currently working on at Mount Stromlo?
A lot of things – probably too many. One of them is a continuation of work which we did in 1998, when we used Type IA supernovae to trace what the universe is doing back into time. These tiny exploding stars end up being even brighter than the massive stars are when they explode, and the interesting thing about these tiny stars is if you've seen one of them, you've more or less seen them all. They're all the same brightness. And so simply by looking at how bright these objects are, we can measure their distance: the fainter they are, the further away they are.
In 1995, just after I arrived in Australia, we started using the biggest telescopes on Earth to discover these objects and figure out how bright they were, and then we would measure how fast each one was moving away from us. In the nearby universe, that allows us to know how fast the universe is expanding. But as we look at greater and greater distances, we're looking not just a long ways away but back into time.
That year, our work in Chile found our first object, Supernova 1995K – not a very exciting name – at 5 billion light-years away. (So it exploded 5 billion years ago, before the Earth was formed.) Finding that first object allowed us to measure how fast the universe was expanding 5 billion years ago, and it indicated to us that the universe was not doing much in the way of slowing down. Yet we expect the universe to slow down, because the universe is full of gravity. Gravity pulls on the universe as it expands, and that should s-l-o-w it down over time. Over the next three years we found a lot more of these objects, which all gave a similar answer to that first one, and that showed that the universe, instead of slowing down like we would have expected, has actually sped up its expansion. It is getting bigger faster and faster. So what we found in 1998 is quite a discovery, and not at all what we expected.
If the universe is speeding up over time, something has to be making it speed up. We had assumed that, basically, gravity was the only thing happening in the universe. This discovery has led us to believe that there is something else, some unknown form of energy which we now call 'dark energy', that is ripping the universe apart. Our 1998 discovery is sufficiently profound and unexpected that we really have to check our work very carefully, so that is one of the things I'm doing right now. Using the Hubble Space Telescope together with the biggest telescopes on Earth we're tracking down as many of these objects as we can and looking at them in fine detail, to make sure something hasn't changed over the last 5 billion years which is throwing us off.
A big-picture view of the universe
I'm excited about another thing that I'm just starting, for which we're using a very small telescope located up at Siding Spring. (It's owned by the University of New South Wales and has been put together by Michael Ashley.) The interesting thing about this telescope is that it looks at a huge piece of sky at a time, and it actually allows us to get a picture of the entire sky about three times a month. Sure, I could go out with my Nikon and do that as well, but this has a very precise look at the sky: it allows us to see things about a million times fainter than the human eye can see.
We can do a few things with this. The first is to make a catalogue of how bright every object is in the sky, and that's useful for a whole variety of purposes.
The second is to look for moving objects, such as near-Earth objects – objects which come screaming by the Earth. These things are typically 100 metres across or even larger, and one of the things astronomers really want to do is to find out where they all are, because objects which get close to the Earth can eventually crash into it. We can usually predict very accurately where these things are going for centuries into the future, so if we know that in 2200 a large one is going to hit the Earth, it would be nice to be able to put a rocket on it and give it a little tap for a couple of hundred years, and keep it from hitting the Earth.
Thirdly, this allows us to find every nearby exploding star in the universe and measure the distance to hundreds and even thousands of galaxies – I can only do tens or twenties now – and to map out the structure of the universe in a way that we've never been able to do before. So that's something that's quite fun to do locally.
Projects to explore the long-long-ago
I'm also working on two projects using the 50-inch telescope at Mount Stromlo, the world's first large automated telescope – we just turn it on and it goes. It figures out if it's cloudy or whatever, and it takes the data. In one project it is looking for new planets just outside of Pluto. We think Pluto is not a planet like the other planets are, but was probably formed from material left over after the formation of the other planets in our solar system. If that is correct, then according to the models predicting it, there should be a large number of objects a little bit smaller (or maybe even larger) than Pluto that we just don't know about. We're looking for these planets, but if we find one we will not be discovering 'another' planet; we'll probably be showing that there are only eight planets, not nine.
While that work is happening, occasionally gamma-ray bursts occur. These are the largest explosions in the universe but we don't really know yet what they are. We do know that with the satellite we suddenly detect a burst from the heavens, for a few seconds, of the highest energy bits of light: gamma rays. So once the satellite contacts us, we have the 50-inch telescope up at Mount Stromlo quit what it's doing and change project to go immediately to that location and try to pinpoint what's going on.
These things, we know now, occur not when the universe was 5 billion years old but when it was 10, 11 and even 12 billion years old. So they allow us to look back to the universe when stars were first forming. The idea is to figure out what's going on in the really early parts of the universe.
So that's more or less what I'm working on right now. It keeps me busy.
An edited transcript of the full interview can be found at http://www.science.org.au/scientists/interviews/bs.
Focus questions
Select activities that are most appropriate for your lesson plan or add your own. You can also encourage students to identify key issues in the preceding extract and devise their own questions or topics for discussion.
astronomy
gamma-ray burst
light-years
supernovae
telescopes
universe
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