Ground-Based Research, Page 3

William Hubbard, on the discovery of Larissa

The planet Neptune has been one of my lucky planets. Neptune’s first satellite, Triton, was discovered in the nineteenth century, and after that there was a long period with no further discoveries of Neptune satellites. That was partly because astronomical instrumentation just had not progressed to the point that you could discover new satellites around this very distant planet. Kuiper—I think it was in the late forties—discovered the next satellite of Neptune, Nereid, which is, it turns out to be, a member of a class of very eccentric, small satellites that are orbiting Neptune. That was one of Kuiper’s discoveries, and it was a nice curiosity.

In 1981 we set up what you’d call a coincidence experiment in the Catalinas, trying to actually look for Neptune’s rings. I was the Principal Investigator on that project. We set up two coincidence experiments. One was on the Catalina 61-inch, which is now known as the Kuiper Telescope. The other experiment was on the 40-inch up on the summit of Mt. Lemmon. The idea was to monitor stars that were passing behind Neptune to see if we could detect rings. We saw a drop-out in our signal on both telescopes, and when we analyzed it, we concluded that we discovered the previously undetected satellite of Neptune. It’s now known as Larissa. I thought it was kind of neat that we discovered the next satellite after Kuiper’s satellite, using Kuiper’s telescopes. In fact, Kuiper is now buried at the telescope where we discovered this.

It’s kind of like deep sea fishing. You have this long line out into space and you don’t know what you’re going to reel in. We pulled in some other interesting things over the years.

Jay Holberg, on ground-based observing

We’re very fortunate here in Arizona because we have four or five observatories. You go up and get ready to make your observations, and you pray for good weather. A couple of nights of bad weather can set you back six months. If you come back and ask for more time, you’re with everybody else, so it’s a bit of a roll of the dice.

But people generally know what to ask for and how much to ask for, and you have a reasonable chance of getting what you want. You go up there and sit in the warm room and look at a monitor, and find your star and make your observations and move on to the next one. You’re up there all night taking data, and you come back down and tell a graduate student to reduce it, and hopefully you find what you’re looking for.

Peter Smith, on searching for extra-solar planets

Space projects in the eighties were rarer than in the late seventies. To keep myself busy, I helped a group looking for planets around other stars. We built an instrument that was accurate down to three meters per second, which is six miles an hour. Imagine looking at the surface of a star watching it pulsing at six miles an hour or higher.

This was before the new LPL addition. We built the instrument on the ground floor near the loading dock. We took a telescope out to the parking lot, and tried measuring the velocity of stars with a 14-inch Celestron telescope using a fiber optic to pipe the light into our laboratory.

Of course we couldn’t see anything but the bright stars. So we looked at Arcturus. I spent two years putting this instrument together and I was really hopeful that we were going to see a steady value, maybe one that bounced around at three meters per second. Instead, the first night we averaged our data, we got a hundred meters per second. The second, it was zero. The next day, it was a hundred again. Very disappointing.

It turns out that Arcturus is not a stable star: It has random pulsations. Nobody knew that; this was the most sensitive stellar instrument ever built. We finally figured out the instrument was okay, but it threw us off our schedule. We took the instrument up to Kitt Peak, where we had a dedicated telescope shared with Tom Gehrels who was looking for near-Earth asteroids. We got the bright time, he got the dark time: We were looking at bright stars, and he was looking at faint asteroids.

We had to spend two weeks a month up there, when the Moon was up. We’d alternate months between me and Bob McMillan. You’d be up there at the 36-inch telescope all alone, nobody but you in this big dome of a building. We only observed in the winter so night lasted 14-hours. You’d set everything up and start your observing. At about four in the morning, you’d battle to stay awake. Every hour we’d shift the telescope to a new star.

We had a TV screen that had an image of the entrance slit to the instrument, and there was a little blurry dot, which was the star. There was a circle drawn on the screen, and you had to keep the blurry dot in the circle. Then there was a counter that had numbers on it telling you how much light entered the instrument. It was like the dullest video game you could imagine. You tried to keep those numbers maximized by pushing the telescope drive buttons. After ten hours of that, your eyes were just dripping, because everything else was dark except for these little red lights. All the red lights would start to swim around.

So to keep from falling face-first onto the table and passing out because it was so dull and boring and you were so tired, you’d walk up to the top of telescope—this was a big dome, maybe five stories high. There’s a little place at the top where, if you climb a series of ladders, you can climb out under the sky. You felt like a sailor in a crow’s nest on top of a tall mast.

You had to be careful on those stairs. There’s no railing on one side and it’s thirty feet down. I remember one time walking up all those stairs, trying to stay awake, at probably four in the morning, and Halley’s comet was visible, rising in the East. I was hanging on, half-conscious because I was so tired, and I felt like was on a ship. I could feel myself moving. I think the wind was blowing. It was amazing because the stars were so bright and beautiful that I tried to reach up and grab one. That’s the joy of astronomy, I think. You see those stars and of course wonder about them and you’ve got your instrument down there and you try to see if there’s a planet on that particular one.

Unfortunately we weren’t too lucky with our choice of targets. There were maybe fifty stars available bright enough for us to measure, and we could only do twenty. You’ve only got 14 hours in the night so you can’t do too many. None of the twenty we choose actually had a planet. It turned out later that the first planets they discovered had a four-day period: A four-day year. We would’ve seen those right away, even at night; I think it would’ve gone right off the charts. If we’d just chosen the right stars, we would have discovered planets back in the mid-eighties. But we didn’t. Now it turns out that for about for every hundred stars, one has a planet.