Observing, Day 1

Saturday, 1:30 PM Eastern time, San Francisco [10:30 AM local time in San Francisco]

I've got an hour to kill in the San Francisco airport until my flight to Honolulu leaves, so I thought I'd check in with my first report. The day started early - I got up at 5:15 AM in order to make it to the airport in time for my 7:00 AM flight. Looking at the alarm clock at 5:15 AM reminded my of the years delivering morning newspapers when I was in elementary school, when I used to get up at that exact time every day. The way I felt also reminded me of why I don't do that anymore....

The flight was smooth - after napping a bit I turned my attention to the upcoming observing run. I've used this telescope before, but not the particular camera that we're going to use to record the data. So I spent some time doing some background reading: a journal article describing the camera's capabilities in general terms, and a manual (downloaded from the web) that describes the detailed operation of observing when using that camera.

Flying over the Rocky Mountains, the aspens looked beautiful. They're starting to change colors for the fall, creating big patches of bright yellow amid the green of the pine trees.

After catching up on the telescope background information, I turned to our particular project. I got out a copy of our observing proposal to remind myself of the exact details of what we proposed to observe for this project.

What's an "observing proposal", you say? Glad you asked. The observing time on large telescopes is allocated to astronomers based on a competitive process. You write a proposal that lays out the observations you're proposing, how much observing time would be needed, and (most importantly) why those particular observations are important for advancing our understanding of astronomy. The proposals are then reviewed by a group of astronomers, who choose the best ones and allocate those researchers certain nights to use the telescope. Sometimes the numbers of nights you are allocated is less than you requested, since the competition can be stiff - typically there are requests for twice or three times as many nights as are available during a given semester. I (along with my collaborators from Wisconsin and Great Britain) submitted a proposal last March for this project, and we found out in May that we had been allocated the nights of September 26, 27, and 28. So here I am, on my way to Hawaii.

3:30 PM Eastern time, over the Pacific

(Got out of San Francisco on time, even though fog had delayed some flights.)

The observing proposal has a list of about 20 stars that we are planning to observe. Three nights should be enough time to complete all of the observations - if all three nights have good weather. But that's not guaranteed, so I start trying to prioritize the target stars. If we only have one clear night (or the telescope breaks) which stars do I want to be sure we've observed? This kind of planning is crucial for any observing run, since you never know what might happen.

I look over the stars in our list, and go over some previous observations (some by us, some by other astronomers) to try to figure out which stars might be most likely to be surrounded by planet-forming disks.

So what am I trying to accomplish on this trip? My main scientific interest is trying to understand how many other solar systems might be out there, orbiting other stars. This is a big question, so I'm working on a small piece of it. That piece has to do with binary star systems. It turns out that our Sun is in some ways an oddball star, because it's a loner, a single star. Most of the stars in the sky (about 60%) are in fact "binary", or systems of two stars that orbit around each other, much as the Earth orbits around the Sun. (Since the Earth is so much less massive than the Sun, the Sun stays essentially fixed in place as we orbit it. When two stars, of approximately equal masses, orbit each other, they both orbit around a common point half way in between them, like two dancers holding hands and swinging each other around.) With these two stars swirling around each other, how can you fit planets into the picture? As you might imagine, it's more complicated than when you just have a single star. And there are so many binary systems out there that if we really want to understand how frequent planet formation is around other stars, we need to know whether you can somehow form planets in the midst of this stellar dance.

Binaries come in all shapes and sizes: equally-matched pairs, small stars orbiting larger stars, and (most importantly for planet formation) all separations. In my past research, I've found that the *separation* between the two stars is all-important. Not too surprisingly, it's not too hard to squeeze in a planet around one or both stars in a pair of stars that are very far apart from each other. Some of the planets that have been discovered in the last few years are in such systems, where the two stars are thousands of times more distant from each other than our Earth is from the Sun. On the other end of the spectrum, if the two stars are very *close* to each other, you can have a planet that orbits both at the same time, much farther away than the separation between the two stars. People on such a planet (though we don't know of any yet) would see two Suns close to each other in their sky.

But what happens in between, when the distance between the two stars is about the same as the size of a typical planetary system? That's what I want to know. All of the stars I'm planning to observe on this trip are binary systems, and in particular, systems in which the separation between the two stars is about the size of our solar system. These stars are too young to have formed planets yet, so we're looking for raw material - disks of gas and dust that may later form planets. These disks don't emit much light in the visible part of the spectrum, but they do "shine" at longer wavelengths. I'll be using the James Clerk Maxwell Telescope, or JCMT, to look for disks by looking for this long-wavelength radiation.

6:50 PM Eastern [12:50 PM Hawaii Standard Time], approaching Honolulu

After spending some more time looking over the target list and examining the properties of the stars, I have chosen several as top priorities for observing tonight: CZ Tau, DF Tau, and FO Tau seem to me to be likely candidates to have disks, albeit small ones. If all goes well, tonight's observations will show whether or not I'm right! But some of my top choices differ from the choices of Bob Mathieu, one of my collaborators, so we'll have to discuss the target list further before heading up the mountain to observe.

6:55 AM Eastern [12:55 AM Hawaii time], on Mauna Kea

I changed planes in Honolulu airport to head for the "Big Island" of Hawaii. I landed in Hilo (the largest town on the eastern side of the island) without incident. I had hoped to catch a glimpse of the telescopes on the summit of Mauna Kea as we approached the island, but I didn't wake up until we were almost ready to land.

From Hilo airport I caught a cab to the Joint Astronomy Center, the local headquarters for the JCMT, where most of the support staff (scientists, administrators, etc.) have their offices. Since it's a weekend there's no one around, but they have left a key for me. I find that I'm supposed to take car #1 up the mountain, and that no one else is scheduled to go up at the same time, so I sign some paperwork, grab the keys, and head out.

The drive from Hilo up the mountain takes about an hour. As I set out, the weather is completely overcast, and soon it starts to rain. I know that doesn't sound like very good weather for astronomy, but I'm not worried. A typical weather pattern on the Big Island is cloudy or rainy down in Hilo, but sunny and clear at the 14,000 foot summit of Mauna Kea. Sure enough, as I approach 8,000 feet, the clouds start to thin out.

At about 5:00 PM local time, I stop at Hale Pohaku (or HP for short), the mid-level dormitory facilities at 8,000 feet, intermediate in elevation between Hilo and the summit. HP is where visiting astronomers for a variety of telescopes sleep and eat, ascending to the summit only for the night's observing. The reason for this arrangement is that it can be dangerous to work at 14,000 foot elevation for too long if you're not used to it, and tired astronomers arriving from various places around the world clearly aren't used to it.

In fact, the telescope safety regulations stipulate that you must spend 24 hours at HP getting used to the altitude before you can ascend to the summit. Thus, you normally want to arrive a day in advance of your observing time. Because of my teaching schedule I wasn't able to do that, so I'll be sitting out tonight's observing here at HP while my collaborators (who arrived yesterday) take care of the detailed observations.

I meet up with my collaborators Bob and Gary at HP, and we discuss plans for the night. We agree on top-priority targets (some of the ones I chose previously, some not), and I spend some time doing a little more background research on them (using data from the web). Meanwhile, Bob and Gary head off to get a little sleep - our observing doesn't start until 1:30 AM.

We reconvene at about 12:30 AM, discuss final plans, and Bob and Gary head for the summit in one of the observatory's 4-wheel drive vehicles. I'm sorry to be missing out on tonight's observing, but at this point I'm exhausted from traveling, so I'm just as glad to let them take care of it.

And with that, I'll end this first (very long) missive and send it back to all of you. More tomorrow.

Day 1 | Day 2, part 1 | Day 2, part 2 | Day 3 | Back to the main page.

Eric Jensen <ejensen1@swarthmore.edu>
Last modified: Sun Jun 8 16:15:39 2003