Michael Bicay, Science Center Manager for the Space Infrared Telescope Facility, explains how a new generation of telescopes is helping scientists explore the universe at wavelengths beyond the range of human sight.
What type of astronomer are you?
My training was actually as a radio astronomer. I used to study the wavelengths of the universe’s radio frequencies, and I did my dissertation research in Puerto Rico at Arecibo Observatory, which is the largest radio telescope in the world. After my post-doctoral appointment at Cal Tech, I started to get involved in infrared astronomy and most of my time now is spent in infrared astronomy.
Most astronomers no longer characterize themselves as simply infrared astronomers, x-ray astronomers, invisible light astronomers. They practice all of these different disciplines, and they do it through a combination of telescopes, some in space, some on the ground.
What is the SIRTF mission about?
SIRTF, the Space Infrared Telescope Facility, is the infrared component of NASA’s family of great space observatories. The first of these, the Hubble Space Telescope, was launched in 1990 and observes the universe primarily at optical wavelengths. This is the same kind of light that the human eye can see.
The second member of this great observatory family, the Compton Gamma Ray Observatory, was launched in 1991. It studies the universe at very high wavelengths that are not visible — gamma rays. This observatory was brought down into the Pacific Ocean in a controlled crash because one of the gyroscopes failed and the mission had already exceeded its lifetime.
The third member of the great observatory program is the Chandra X-ray observatory. This was launched from the Shuttle and is exploring the universe at x-ray wavelengths producing some spectacular results.
The fourth and final component of the great observatory program is the Space Infrared Telescope Facility. It will observe the universe at longer, infrared wavelengths.
Who will be able to use the SIRTF observatory?
For the most part, when NASA launches these large observatories, most of the observing time on them is open to anybody who is trained as an astronomer.
There is a competition; you write a proposal and you say, “Here is what I am going to do, this is what I would like to study, here is how I am going to do it.” The best proposals then receive observing time on the observatory. Typically, for every six proposals submitted, only one of them gets approved.
Why do we need to study these different wavelengths?
The reason we study the universe at different wavelengths and with different types of telescopes is because phenomena in the universe emit different kinds of light. For example, the most explosive events of the universe, the explosion of massive stars, what we call super novae, emit large amounts of x-rays and gamma rays. Most big stars, like our sun, emit primarily visible light. So you can go out and see the sun. It’s a typical star, and you can see many stars in the sky with visible light. If you look at longer wavelengths, such infrared, you start to also see different phenomena, namely dust in the universe.
Why is dust important?
Apart from the fact that stars are born in cocoons of dust, it is thought that planetary systems form in dusty environments. Our solar system currently exists as nine known planets, many moons, asteroids and comets. It wasn’t always like this. About four and a half billion years ago, it is thought that it was nothing more than what we call a disc of dust circulating around the sun – much like a hockey puck.
Because of the influences of gravity, slight densities, irregularities within that disc, started to coalesce and coagulate and formed small planets. What we would like to do with SIRTF is survey nearby stars and find out if there are any planetary systems in the act of formation.
Have we ever seen planets around stars other than our sun?
We have come to learn that there are planets around other stars – this is a new, recent discovery over the last five years – but we have never actually seen one of these planets directly. We can only infer their existence through the small gravitational fix that these planets have as they tug their star back and forth.
NASA’s long-term goal in space science in the next fifteen years is to actually image planets around other stars. But before we get there we have to know which stars are most likely to be candidates to have planetary systems. One way to do that is to characterize the planetary systems before they create planets. So we will look at many hundreds of nearby stars, we will be able to image discs of dust around these stars, we will be able to do a chemical analysis of what the dust particles resemble.
What do you think the biggest breakthroughs will be?
There are two big breakthroughs coming through, I think, in the next ten to fifteen years. SIRTF, as I mentioned, is the last of the great observatories and is essentially a meter-class telescope, which means the mirror in the telescope is about one meter wide. That is the largest telescope that we can typically launch into space now at these wavelengths.
The next big step will be to launch very, very large telescopes in space. The mirrors in these telescopes will not be solid mirrors, they will be folded up much like the petals on a flower. That is the only way you can fit them in the rockets to get them into space. Then when they get into space, the mirror segments will unfold and create a very large aperture. This is the principle behind the successor to the Hubble space telescope, the Next Generation space telescope. We hope to launch it in about 2009.
The second area is to actually take telescopes and link them together; link them electronically and create the equivalent in terms of angular resolution of telescopes that are many hundreds of kilometers across. It’s what we call that interferometry. It has been done in radio astronomy on the ground since the 1940’s and 1950’s. But our goal is to do it at optical and infrared wavelengths in space.
What will better telescopes show us?
We will be able to peer deeper into the universe and to understand how galaxies and stars form. We want to find what we call primeval galaxies, the precursors to the spiral galaxies and the elliptical galaxies we see now.
You need a variety of telescopes to address the question of what is the fate of the universe. Ultimately the fate of the universe is a function of how much “stuff” there is in the universe, and whether the gravitational influences on all that stuff, what we call matter, will eventually slow down the expansion of the universe. We don’t know for sure what the answer is yet. Recent evidence suggests that there is enough matter in the universe to slow down the expansion, but not to necessarily halt it. The universe started in a “big bang;” we think it is about 14 billion years old. We think that it will continue to age, and that the universe will continue to expand, but we don’t for sure what the ultimate fate of the universe is.
What do you like best about your job?
The fact that I get to participate in an exciting endeavor that has captured the imaginations of humans since we crawled out of caves and looked at the night time sky. Astronomy has been with us for thousands and thousands of years. Since Galileo built the first telescope in 1609, our capabilities continue to get more and more sophisticated. We can now launch large observatories into space.
Every time we do so, we go up there with the intention of answering some questions – but inevitably, the universe offers some phenomena we have never seen before. For every question that gets answered, we raise new questions. Then we have to go back to the drawing board and build a more capable telescope for the future. It is this evolution of knowledge, knowing that knowledge changes and is not static, that I think is so exciting.