Planet formation
Solar system
Disks of matter

So if you lived in one of these systems near the star, you would get essentially the same kind of thing that we have here in our own solar system. That is to say the region of sky where planets would form would be in a band in the sky just like all our planets move in a band around our sun. And because these disks form along with the star, the whole cloud that makes both the star and the disk collapses together so everything’s moving in the same direction. So you would also get any planets that form in that disk would all orbit the star in the same direction just like we have in our solar system.

All of this was very suggestive that planet formation was certainly possible and could be common. But of course we didn’t have any evidence of planets themselves. But astronomers’ theories about star and planet formation were greatly aided by these observations because for the first time, instead of just theorizing about how this happened, we were able to observe actual instances of it happening.

The process of star formation takes a few hundred thousand years to a million years so you might wonder how we can learn about given that we’re only looking at it for a brief amount of time. The trick to that is we just observe stars that are in different parts of that process. So just as you can put together a picture of how humans grow up and die by looking at a crowd and finding some babies and some kids and some teenagers and so on, we do that with stars and look at stars in all the different phases of star and planet formation and can put together a whole picture of how this works.

There are various ideas about how the dust can form up into somewhat larger grains as we call them as they start to look like grains of sand, for example. One idea is that just sort of electrical forces between the particles may cause them to clump and there’s even been an experiment on the space station in which this actually happened for an astronaut. They were actually able to get dust-like stuff to clump into bigger clumps just because of electrostatic forces. At any rate, this is certainly an area of current research and we aren’t sure what the answer is. Once you get past that point though then it becomes easier for a while to build up larger bodies and what happens from an observational point of view is that as the dust begins to clump up, the infrared signal from it starts to go away because the dust is now collected into larger objects so there’s much less surface area to emit infrared if you put it into a snowball than if you spread it out in a big cloud of smoke. So we actually see that happening around young stars. That the infrared signal is going away and that it goes away even from one part of the disk before it goes away from another part of the disk. Even in some disks we can see a signature that it looks like a certain orbit around the disk is getting cleared out of dust. All of those of course are very suggestive that something bigger is forming in those places. At this time, although we can’t actually see planets forming yet, we have a lot of indirect evidence that that process is happening.

Like many astronomers, I think I got interested in astronomy as a kid. I can remember being very interested by the time I was 7 or 8 years old. I actually would credit science fiction as one of the reasons that I became interested in astronomy because although I like looking at the stars, I hadn’t actually thought about traveling there or what might be out there until I began reading science fiction which happened fairly soon after I began reading at all. So I think science fiction got me interested in thinking about outer space and then I wanted to learn more about outer space and that’s really what got me interested in astronomy.

When I was the director of this institute, one of my jobs is to constantly show that the program is worthwhile, so I’d have all the numbers. I’d get people like Cheryl here, we’d find out how many papers were published, how many new discoveries were made, how many times there were major news items that had to do with Hubble and its discoveries, and what was interesting is you could see that after the servicing mission in 1993 the line just took off like a shot, just ramped up in a way you could see just stuff pouring out. After about 3 – 4 years it would begin to roll over a little because you’d take advantage of all that technology, but now this is the real miracle of Hubble, and I think frankly a lesson for us is, Hubble was not just designed to be fixed in space, but it was designed to be improved. So the same astronauts that went up and fixed it could go up and could swap instruments out, and improve it.

And this is no small advance. Because if you think about it and this was during the 90s, think about most people have home computers, a lot of them have laptops. My laptop now has more power by some huge factor, I mean a factor of probably a million compared to the computer I learned to program in college in the 1970s which was a big IBM 360, a huge thing that filled up a room, it was a big deal. I carry more power around now and can put it on my lap, can use it on an airplane, much more. And this is just because the advance of technology has made computing and electronics so much faster. The same thing occurs in astronomy with instrumentation, mostly with detectors.

There are so many, I couldn’t pick just one. I could mention some names, obviously Galileo was a tremendous inspiration to us all, as was Hubble. Some of my modern heroes, I’ve been very privileged to know Charlie Townes. He invented the laser but after he had already become a complete icon of 20th century physics and invented the laser he turned his attention to astronomy and has brought new technology in there and just done wonderful things and he’s just an absolute, to me an icon. I’ve had the privilege of knowing Ed Saltpetre at Cornell and Carl Sagan, and there are just many, many great scientists. All of these people have provided me with inspiration in different ways, and I unfortunately couldn’t settle on just one.

The photographic plate, which for years was the thing that you had on telescopes, it turns out that the photographic plate is a pretty lousy detector. A photographic plate only captures a couple percent of the photons of the light that impinges on it. Most of it just doesn’t register at all. So it was great at the time, but it’s rotten. The eye isn’t all that great, there’s a limit to what you can get with the eye. But nowadays we can create detectors, which can capture essentially all of the light falling on them and record it, which is an enormous advance.

The other thing is, these detectors kept getting bigger and bigger, and the information capacity that you get in an image is really a product of two factors – one is the number of pixels, the number of individual picture elements, resolution across is, and the other is the depth, how sensitive it is. Both of these were improving just like Moore’s Law for computers, they were improving by huge factors every few years, doubling in capacity every two or three years. And so what happens with Hubble, is that you take a telescope and by changing the instrument you can make it about ten times more powerful, or more. We’ve put instruments on Hubble which have improved its detection ability by a factor of 50 or more, just by changing the instruments. You do that and you get a whole new telescope. It’s just as if you had started from scratch and had launched a whole new one – so, it turns out that on NASA’s schedule you could do this every 3 or 4 years and it was to a large extent limited by money, because it’s expensive to do, but not so much by technology.