Day 2 of our science teacher workshop

Participant Jesse Whitaker explores the properties of light.

Here with another special report from the McDonald Observatory "Age of the Milky Way" teacher continuing education workshop is participant Dan Maloney:

Day 2 Summary – Yesterday was another very informative day for the teacher workshop. The group was led by our mentor teacher Jody through several classroom activities. The first was on the life cycle of different stars, and the second was on light spectrum analysis. For the life cycle of stars students blow up different colored balloons to learn what they eventually “explode” into. Students will definitely be surprised by how the death of a star occurs. For the light spectrum activity students examine how different colors of the spectrum change under various conditions. Both activities foster inquiry based learning and are suitable for a wide range of science and astronomy classrooms.

For the second night we have been not able to get in any observing time due to the weather but we are very optimistic that the weather will clear before the end of the workshop. Despite the weather we have been busy learning about white dwarfs and the group has started our preliminary analysis on white dwarfs using the imaging software program called ImageJ.

The group was also treated to a tour of the 82 inch Otto Struve telescope, which was built in 1938. The telescope is engineering masterpiece that is fully functional and serves astronomer in a wide variety of astronomical research. Today we will be touring the Hobby-Eberly telescope. I can’t wait.

Cloud happens

Tonight has not been a fun night at the telescope. At sunset, it was completely cloudy, but the cloud forecasts from the Clear Sky Chart claimed it would clear by 1am, so we hunkered down. Within an hour, the skies overhead cleared, so we opened the dome and started our observations.

However, the clear spot was what is known as a "sucker hole," meaning you are a sucker to think you can get good data. After about 45 minutes, the hole closed, and the skies have been mostly cloudy ever since, always teasing to clear, but never good enough to start working.

In another half hour, I'm giving up if it is not clear. Our observations need several hours to be worthwhile, and it is four hours to dawn now. I could be trying to work, but sometimes no data is better than bad data. Hopefully tomorrow will be better!

Observing in west Texas

It's been a busy few days here. Tuesday I went to speak with students in a couple of high school astronomy classes in Kyle, Texas (a little south of Austin). It was an interesting experience. Some students were interested in what I had to say, some were interested in asking me questions but on topics other than what I was talking about, some were bored and passing notes or texting during class, and others were sleeping. That visit was a lot of fun. but it took a lot out of me. I would not be able to get in front of that group every day, though.

Wednesday I drove out to McDonald Observatory for a weekend of observing. The drive was worse than normal. I had a 30 mph headwind, with occasional gusts that nearly blew my poor little car off the road. Because of the headwind, my gas mileage wasn't very good, and I slowed down to keep better control of my car. In the end, I arrived too late for dinner (but there were leftovers).

My goal is to do some more observing of our pulsating carbon atmosphere white dwarf. In order to use these pulsations, we need to get many nights of data spread out over time. This is our first real push to get lots of data on this star since we discovered it.

So, keep your fingers crossed for good weather. We may get a lot of clouds here later tonight and the first part of tomorrow night.

traveling and telescopes

Last week American Airlines had to cancel a couple thousand flights due to mechanical issues. Many people who were supposed to fly (like me) ended up staying home. I personally know people who missed out on weddings and important meetings because of all of the chaos. Airlines can be sorry all they want, but when people miss events like weddings and funerals, there's no way to apologize properly.

Anyway, what happens to astronomers who miss a flight to a telescope? Telescope time is a rare commodity for many astronomers. A few nights a year at a large telescope is enough to keep most observers gainfully employed. Telescope nights are typically scheduled 6 months in advance, and there is almost no flexibility in the schedules of most telescopes. So, what happens if you can't get there?

For most telescopes, the astronomer is out of luck. Often the astronomer is solely responsible for the telescope; if there is a telescope operator, that person is quite knowledgeable about the telescope and the mechanics, but would not be able (or willing) to do an astronomer's observations for her. For that reason, many astronomers (myself included) travel a day or more early to the telescope. The extra night can be used to settle in and to start to get on a night schedule.

I've had to use that extra day several times, especially when I fly to South America. If I miss my connection, or the intercontinental flight is delayed for 12 hours (which happens quite a bit!), there is no option -- I'm going to arrive 24 hours later. It is awful to hop off of a 7000 mile plane trip and then stay up all night, but some times it has to be done.

In some cases, observatories are set up for "remote observing," where the astronomer can be thousands of miles away and observe over the internet. This runs risks, such as the internet going down, but some people prefer that risk to travel, and sometimes it can't be helped.

After the terrorist attacks of September 11, 2001, all air traffic was stopped for several days. At least one astronomer in California had time on the Keck telescopes in Hawaii, but obviously wasn't able to get there. So, he drove from Pasadena up to Santa Cruz, where there was a room that was set up with all kinds of cameras and computers for observing, and he was able to use the telescope quite successfully.

But few observatories offer remote observing. It is expensive and time-intensive to set up (although it can pay for itself in very little time), and it brings new technical challenges. How can astronomers know they are getting high-quality data, if those data will take hours to transmit across even the fastest internet? Without the ability to step outside, how can the astronomer know what the weather (specifically cloud cover) is like? And are the telescope operators willing to take the extra training they would need to troubleshoot bad internet and other issues that the astronomer would normally take care of? These problems are more difficult than they sound, but they are not impossible to solve. The number of telescopes with remote operations capabilities continues to grow, albeit slowly.

For telescopes withot remote operations, however, not arriving at the telescope means no data. Sometimes you may have a friend you can call to do you a big favor ("Hey Bob, you weren't doing anything tonight anyway. How about staying up and taking data for me?") It's a chance we take, just like the chance with the weather. Often you can request new time at the telescope, and the committees that assign time will take bad weather or travel problems into account (provided that the problem is severe -- missing several nights because of poor planning does not endear one to these committees). But there is no guarantee that you will ever get that telescope time again -- maybe someone else will do the project first at another telescope, or maybe the science you propose to do loses its luster. And, often you have to wait an entire year for more telescope time, because most stars are only visible at certain times of the year.

So, when an airline grounds over half of its fleet, astronomers can be in quite a pickle, too. Like everyone else, we wring our hands, blow steam out of our ears, and deal with the consequences.

How fast is it?

Image Credit: Speed Measurement Laboratories Inc.

This weekend I worked on trying to measure how fast a certain star was moving. It didn't go very well. It's an interesting star (a white dwarf with a very strong magnetic field that is pulling gas off of a companion star), and I found the star by accident in some data I took a year ago. Because it was a serendipitous discovery (meaning I was looking for something else), I didn't get quite the right measurements, and I'm trying to kludge something together.

You will often hear about astronomers measuring how fast an object is moving. We detect planets around other stars by measuring changes in the star's speed caused by the planet's gravity. We know that the Universe is expanding because all distant galaxies seem to be moving away from us, at faster and faster speeds the further we look. How do we measure speeds of stars and galaxies?

Astronomers use a technique called the Doppler Effect. The one sentence summary of the Doppler Effect in astronomy is that an object's movement slightly changes the wavelength (or "color") of light coming from that object.

A police radar gun uses the Doppler Effect. The radar gun sends out radio waves with a wavelength of about 1/3 of an inch (or a little less than 1 cm). The radio waves bounce off your car, and the car's motion causes the wavelength to change a little bit. The radar gun measures the change, and calculates the speed of the car. And, as long as the police officer has remembered to calibrate the radar gun (by pointing it at something that isn't moving; many radar guns do this automatically now), the measurement is pretty accurate.

The only difference with measuring the speed of astronomical objects, like stars and galaxies, is that we don't send out a light beam to bounce off of the star. That would take decades to millions of years to get a measurement! And, it's not needed, since stars and galaxies put out their own light. Another small difference is that astronomers tend to use optical wavelengths of light, which are only the size of a bacterium, and it's much harder to measure the differences in that wavelength than the radar wavelengths of a third of an inch.

But, like the police officer, we have to make sure to get proper calibrations. Astronomers use several different calibrations. We have lamps that emit light at only very certain wavelengths, and we know those lamps are not moving. We can use Earth's own atmosphere, which glows faintly at very specific wavelengths, as a double-check. And, to triple-check the measured speeds, we look at stars with known and well-measured speeds. Astronomers looking for planets sometimes even use a fourth level of calibration, by making the starlight to pass through a container of iodine gas (which absorbs light at many very specific and unchanging wavelengths).

My problem: I wasn't out to measure the speeds of stars when I took my data. So, while I did use the lamps I talked about above. At the certain colors of light I was looking at, the atmosphere doesn't glow. I didn't look at a star of a known speed (I didn't think I'd be needing that information!). And, since I wasn't looking for planets, the container of iodine stayed safely stored.

So, I have some very accurate measurements of changes in the star's speed during a single night, because I can inter-compare all the data I took. But I don't know the absolute speed. (It'd be like a police officer measuring that you slowed down by 15 miles per hour once you saw the cop car, but the officer not knowing if you were ever actually over the speed limit).

Yes, I could go back to the telescope and get a new and proper look at this star, but I need to try and make do with the information I have first. I have a few more tricks to try, too. We'll see what happens.

Looking for proper motions

Image Credit: Sebastien Lepine/SUPERBLINK

Yesterday I mentioned that I am here at Kitt Peak outside of Tucson, Arizona, working on a project to image a large fraction of the sky.  So, why are my collaborators and I trying to image 1/4 of the entire sky visible from Kitt Peak?

The part of the sky we were looking at was imaged between 1999 and 2005 as part of the Sloan Digital Sky Survey, which mapped a large fraction of the Northern Hemisphere sky in five colors.  So, at first glance it may sound silly that we are getting new images of part of the sky that was just mapped within the last decade.

While the stars in the sky appear to be fixed, with constellations staying the same from year to year, generation to generation, and even millennium to millennium, all stars are slowly moving around the Milky Way galaxy.  It takes stars like the sun 250 million years to orbit the Milky Way, so in a human lifetime, we don't cover much of that orbit!  

But, with precise measurements, it is possible to see that the stars are slowly moving in the sky.  If you brought an ancient Greek to modern times, he or she would notice that a few bright stars have moved noticeably in 2300 years.  But with more accurate measurements, we can use ground-based telescopes to measure changes in position as small as about one hundred thousandth of a degree, or about the size of a bacteria seen from 30 feet away.  These star motions are called proper motions.  

The closer a star is to us, the larger its proper motion, on average.  Some nearby stars can move quite a bit, as in the picture above, which shows one red dwarf star moving a large distance (still only the tiniest fraction of a degree!) 45 years, while the other stars appear to stay still.  This particular star is only about 35 light-years away from the sun, while the other stars in the image are probably hundreds of light-years away.

We are looking for the faintest white dwarfs, the remains of dead stars that are slowly cooling off and fading away.  The faintest white dwarfs we can find are therefore some of the oldest stars in our Galaxy, and we hope to use these white dwarfs to tell us how old various parts of the galaxy are. (If we know how faint they are and how fast these stars fade, we can estimate how old they are).  Like the red dwarf in the picture above, faint white dwarfs tend to have relatively large proper motions.  So, although only five years have passed since the first images were taken, the stars have moved enough that we can measure the movement. 

If we showed you most of the stars that have measured motions, you probably wouldn't believe it.  The motions are very tiny, smaller than the spot size of the star.  But my collaborators can still measure a slight shift in the center of that spot!

So, that's why we're here -- searching 1/4 of the visible sky for maybe a fifty or a hundred of the oldest stars in our galaxy, out of millions of stars we'll be imaging.  Hard? Yes!  But the science result will be worth the work.

Looking through Hubble

Friday was a day that many observational astronomers dread. It was the day that the time allocations on the Hubble Space Telescope were announced. Some of you may remember my writing about this proposal back in January. I submitted a proposal, and 12 hours later, Hubble's camera that I had asked to use quit working. Because so much of the time astronomers asked for used this camera, and because the deadline had just passed, NASA extended the deadline for a couple of weeks.

Two weeks ago, while I was learning about exploding white dwarfs, dozens of astronomers met in Washington, DC to choose which of the proposals would get time on the Hubble telescope. It was a tough job, as astronomers asked for over five times more time than was available. And this was after some large programs were knocked out because they required the now-defunct camera!

When so much time is requested, it is inevitable that perfectly good requests are denied. So, I felt absolutely ecstatic when I learned that I was granted Hubble time. For the first time ever. And I was worried that I was asking for a lot of time, which can hurt a proposal.

It may be 15 months before my images are taken, and I have to keep my fingers crossed that nothing else breaks before I get my data. On the good side, at the end of the next 15 months, astronauts should be up fixing the Hubble one last time.