Martin Still, Ph.D.
Director, Kepler Mission Guest Observer Program
Kepler’s primary scientific goal is to detect terrestrial planets in the habitable zone and the frequency in which they occur, however, the data the photometer is providing the scientific community reaches far beyond the search for exoplanets. In order to get a sense of Kepler’s depth I sat down with Martin Still, Director of the Guest Observer Program and newly appointed Deputy Science Office Director.
A Day in the Life
What stands out to Martin more than any job he has had previous to this is that no one day is exactly alike. “No matter what you have planned for your day you don’t always get it done because there’s a new issue to resolve as soon as you arrive at work, this has to do with working on a new mission. The mission is unique and novel so operational experience is being learned on the fly rather than inherited from past projects. Every day is filled with learning how to do new things and unlearning how to do old things. The overarching feeling as the weeks and months go by is that we are making grand waves. I have enjoyed watching the project evolve; it has grown considerably. When I started a year ago, the startup job within a small team was much more hands on; at this point, with new recruits onboard I’m able to spend more time scoping and directing our efforts. I’m now able to take a step back, draw breath and lean on the support of both the existing team members and a lot of new people who have joined the mission. They have come in with research experience whether it’s exoplanet or timing related astrophysics, these new team members are really good at what they do. I’m there to scope out their work, make sure that their path ahead is clear and that they have all of the resources that they need. Somewhere between one half to three quarters of my day is spent in a management or operations meeting of one description or another. The rest of the day is spent making sure everyone is happy and they can get on with their work, driving towards our mission goals.”
GO Program Overview
The Guest Observer Program can be seen as a facilitator with a two-way door. In order to be successful we have to be a clearinghouse for much of the mission’s operational information. If you are an astrophysicist working at a university or an institution anywhere in the world and you want to be able to do science with Kepler it takes enormous understanding of the capabilities of the mission. You have to know its strengths and limitations; when you’re looking at Kepler data you need to be able to recognize what is astrophysical signal and discriminate it from instrumental artifact. Anyone who chooses to participate needs to collaborate with the Guest Observer Office so they understand as much of the technical information as possible and each participant knows what they can get out of the mission. The Guest Observers reach out and ask for help in understanding a piece of information out of that data. The program’s success is judged by the amount of scientific papers that are being produced, the number of universities working on Kepler data and the number of scientists aware of the mission and what it can do.”
GO Proposal Process
“Guest observing is based around peer reviewed science proposals. In order to write a successful proposal you have to be an expert in your field. Amateur astronomers are not excluded from the program at all, however, the best advice they can get is to collaborate with a professional astronomer since they are in the business of writing competitive scientific proposals. The panels that decide what programs get followed and what targets get observed look for any reason to throw a proposal out because there are so many good ones to choose from—it’s very much survival of the fittest. If Kepler doesn’t observe the most competitive and the most exciting science it will struggle in the future. Each proposal has to be more compelling than the next. If one wants to become a Guest Observer you would submit a proposal with a very well-defined scientific goal and propose to answer a specific scientific question. The most compelling questions are the ones that will be chosen. When it’s time to choose among the proposals, NASA headquarters and the Guest Observer office collaborate to lobby the scientific community to provide independent scientific advisors. They discuss each proposal on merit in a closed room full of cookies and coffee. Each person has an equal vote; seven or eight experts make the decision. These experts come from all over the country and even the world. In order to keep the process fair and unbiased the panel changes every year. It’s made up of a mix of senior experts and new young post-docs with a huge spectrum of scientific interests and ideas. The goal is to have the best mix of professional astronomers that can be found.”
A paper that appeared in the press recently is a discovery made by Kevin Apps, a 25 year old undergraduate from the UK who found a new brown dwarf object by mining Kepler’s public data. Martin explains, “A brown dwarf is somewhere between a gaseous planet and a star. It’s a cold star, just a few thousand Kelvin in temperature. This brown dwarf is only the fifth transiting brown dwarf known to exist. Not only that, its transit shape has been fit with a model and its mass measured by ground-based spectroscopy. Because of the photometric accuracy of Kepler, the measured radius of this brown dwarf is many times more accurate than any of the other four discovered. This discovery is wonderful for Kepler and for the amateur astronomer. It shows that there is potentially a problem in the theory of brown dwarf atmospheres. The observation does not fit current theories of brown dwarf size, being too large for an object of its perceived age. Kevin called on prolific professional planet-hunters to put this discovery into a paper.” In Martin’s view this is one of the most exciting papers that has come out of the Kepler community outside of the Science Team and exoplanet world. “This is what I love to see and why the Guest Observer program is so important. Kepler’s endeavors cannot be performed by the Science Team alone, there’s just too much work to be done.”
Martin did his Ph.D. in the field of cataclysmic variable stars. “These things are wonderfully dynamic in terms of the way they changed rapidly over time. They are binary stars orbiting very close to each other on a few-hour time scale, flashing past each other, they’re so close that one of the stars is actually grabbing material from its neighbor and you get this bridge of gas between the two. This gas is falling onto what is called the accretor, which is a white dwarf star whose surface undergoes regular ‘cataclysmic’ explosions. These were fantastically sexy objects to work on back in the 70’s and 80’s with great relevance to the formation of planets, stars and black holes, but as time went by, accretion disk theory overtook the observational capabilities of ground-based and space-based telescopes; it overshot it dramatically. The only way that many people, myself included, believed that we were going to catch up is to have a 100-meter telescope on the ground—a super telescope, equipment that will not be available for at least another decade. When I joined the Kepler team, this mission’s ability to open a unique and valuable new window on these objects was immediately apparent. The first thing I did was to ask the target schedulers to put apertures over the few cataclysmic variables that are in Kepler’s field of view. These things are quite ubiquitous, there are thousands of them that we know of in the galaxy but most of them are quite faint including the ones in Kepler’s FOV. There were none that stood out, no fantastically brilliant ones that were famous and that people always worked on over previous decades. They had barely been looked at. However, when the data came through it was amazing, these data have enormous value. I was back to being a cataclysmic variable fan. Kepler is doing something unique that no other telescope can do, it’s sparking enthusiasm in this field and a body of critical work.”
The data that Kepler is providing has actually brought tears to the eyes of scientist. The first time Martin saw a light curve of one of these cataclysmic variable discs he admits that he “got a bit misty; Kepler evokes an emotional response in many people. The final product of the Kepler observations of cataclysmic variables could be putting a value on a particular number that is extremely important across the whole of astrophysics and that’s how ‘sticky’ what we call an accretion disk is. The reason why this is so important is that almost everything in the universe formed out of an accretion disk. Stars formed, planetary systems around stars formed from within these disks. These disks also surround the massive black holes around active galactic nuclei. Kepler is observing accretion disks with a combined photometric precision and time sampling that nobody has ever been able to do before. While it’s not producing scientific quantities that haven’t been estimated before, it is improving the accuracy of what we know about these accretion disk properties by an order of magnitude, which is a big step forward.”
Kepler’s Contribution to Stellar Activity
“One of the things that Kepler does really well, not necessarily because of its photometric precision but because of its ability to stay on the same piece of sky observing the same stars, is that it’s producing an enormous legacy catalog of spotty stars; just like our Sun has sunspots that come and go on an eleven-year cycle. Sometimes the Sun is very spotty around the equator; it has a lot of dark patches, which are related to the magnetic activity within the Sun being generated by convective motions below the surface. Many other cool low-mass stars for which the Sun is included have a similar mechanism going on across their surface layers. Kepler can actually see star spots on distant stars developing and going away. You can use the spots on the star’s surface to measure the rotation speed of the star, which is very important parameter in the life of a star. Young stars rotate very rapidly; they formed out of a cold cloud and they spin very fast when they are young. As they mature and get older they slow down and become more sedate. As they become more sedate the number of spots gets smaller. What Kepler gives us is a wonderfully broad look at the evolutionary state of a star. What will be truly amazing is if Kepler continues its mission beyond the primary years through 2012. If it gets another two or three years, just a little bit longer, then you approach the time scales of the magnetic activity cycles. The Sun is eleven years; many stars are less than 5 years. This kind of opportunity to observe these stars has never been provided before, being able to take 30-minute cycle samplings of highly precise photometry of one star or thousands of stars for five or six straight years would be unprecedented. We will be able to see the activity cycles of thousand and thousands of stars, which will be awesome.”
The Depth of Kepler
“We can only infer the structure and property of a star from what we see on the surface. This requires both observation and theoretical modeling to record what the surface of the star looks like. In that process there’s always redundancy. Kepler has the ability and the accuracy to record in great detail and precision the ways and modes of surface pulsation across many stars. Nothing else on or off the planet can do it with anywhere near the same degree of fidelity. These pulsations are basically driven by areas of instability, storms on or close to the surface, on the surface or even deep down in the core of the star. When you see these pulsations it’s a direct measure of things that are going on either deep in the interior or close to the surface of the star. There are phenomena you wouldn’t be able to detect on the surface of the star any other way, other than Kepler. It’s the only instrument that can do this work that precisely for that duration of time. This isn’t a new field of study. People have been doing this work from the ground and from space for decades. However, Kepler has blown the field wide open! It is still model dependent, you have to provide the theory to explain the observation and it’s the theory that tells you about the structure of a star. However, because the observations are that much more precise, the theory has to be that much more precise. Before Kepler there may have been five theories to explain what you were seeing, perhaps now there are only one or two. And of course that’s not to say the theory is correct. In science your theory only stands until proven incorrect. The other thing that Kepler is going to do over the years is to build a legacy database and those theories, every day, week, month and year still have to explain what you are looking at and if they can’t, they’re wrong. Kepler is driving this field of science and is teaching us more about the interior of stars. It’s like a rapid injection of understanding; things that might take decades to understand without Kepler will be learned on a much shorter time scale.”
Meaning of the Mission
I was curious to know what it would mean to Martin if Kepler were to find an “Earth-like” planet. “I fully appreciate that my personal views are heretical, but that’s why I was asked to run the Guest Observer Office, I don’t see exoplanets as the richest area of science that Kepler is pursuing. While time may prove me wrong, I feel that the habitable zone exoplanets that Kepler is searching for are almost certainly there. Their discovery is inevitable within the next few years either by Kepler or another project. For me, the beauty of Kepler is the other science that it’s doing. It’s re-exciting areas of astrophysics that have been quiet over the last 20 years, and promoting those areas which have been noisy but is contributing to them in new, significant ways, providing that extra step. If we are being honest and truthful with ourselves, the exoplanet mission provides enormous interest for the general public. However, in terms of NASA’s mission to understand the origin and structure of our universe, Kepler’s other activities provide a legacy which history may well regard to be of equal scientific importance.” Martin loves working with the Kepler team, “It’s a fantastic environment to work in, who wouldn’t be excited to work on this mission.” To read more about Martin’s educational background and prior work experience, click here.
By Kepler blog contributor, Marlowe Primack