While analysis of the Kepler mission data proceeds, we continue to operate the spacecraft for the K2 mission. In the Mission Manager updates, I’ll provide periodic posts on the spacecraft operation, the team and the latest science results from the Kepler and K2 data. In this blog I’ll give you a view of the work we’re doing, and the various issues that we have to consider.
Kepler and K2 mission manager
NASA’s Ames Research Center
This week Natalie Batalha, NASA’s Kepler mission project scientist, is in Cambridge, Massachusetts, where she will receive the 2017 Lecar Prize from the Harvard-Smithsonian Center for Astrophysics (CfA). The award, now in its fourth year, recognizes exceptional contributions to the study of exoplanets — planets outside our solar system — and theoretical astrophysics. Batalha is the first NASA employee to receive this honor.
“The scientific success of the Kepler Mission is the direct result of the vision, creativity, persistence and leadership of people like Natalie Batalha. Dr. Batalha is one of those very rare people who are not only gifted scientists, but who can also marshal the talents of a diverse group of engineers, scientists and managers toward the kind of phenomenal success that Kepler represents,” said Matt Holman, chair of the prize selection committee and senior astrophysicist at CfA. “We are thrilled to be able to recognize Dr. Batalha’s contributions to exoplanet science by awarding her the 2017 Lecar Prize.”
The prize is named for Myron S. “Mike” Lecar, who was with the Smithsonian Astrophysical Observatory from 1965 to 2009 researching planet formation and the dynamics of gravity and our solar system.
Each Lecar Prize recipient is offered an honorarium and delivers a lecture at the Harvard-Smithsonian Center for Astrophysics. Batalha will give her lecture on April 6, about Kepler’s forthcoming final planet catalogue and the measurements of the survey completeness and reliability required to study exoplanet populations.
Batalha has been with the Kepler team since the space telescope was still on the drawing board, and has served in various science leadership roles. She led an analysis that revealed the first rocky planet Kepler found outside our solar system, called Kepler-10b, in 2011. Now, as the project scientist for Kepler at NASA’s Ames Research Center in California’s Silicon Valley, Batalha is preparing for the end of the prime mission. That will come when the team delivers its final planet candidate catalog and associated data products in the summer of 2017.
Batalha took some time recently to talk about her work, about having a role model, then becoming one, and about watching her daughter follow in her footsteps.
How do you describe your present research?
I work on planet detection, characterization, and occurrence-rate studies. I’m also starting to turn my attention toward the broader subject of planetary habitability. With Kepler, we sought to find planets in the habitable zone (the range of orbits where liquid water can possibly exist on the surface). The long-term goal is to transition from finding habitable zone planets to finding habitable environments, and even living worlds.
Kepler was funded to do something very specific: determine the fraction of stars that harbor potentially habitable, terrestrial-size planets. That is what we mean by “occurrence rate”: how frequently planets of a given size and orbit occur in the galaxy. Kepler has delivered a statistically significant sample of new discoveries, thousands of planets that we can study as a population. We find that small planets are much more common than large planets in the inner regions of a planetary system. M stars (red dwarfs) seem to make terrestrial-sized planets more frequently than G-type stars (like our sun). We’re able to study these more general population-type questions because we have such a large sample of discoveries.
What else has Kepler taught us?
Kepler has demonstrated a diversity of exoplanets that we didn’t expect. For example, the most common planet known to humanity right now is one we don’t even have in our solar system: these super-Earth, sub-Neptune type planets. We don’t know anything about them. We don’t have any examples here at home.
We have found lava worlds with one hemisphere that’s an ocean – an ocean not of water but of molten rock. We have found disintegrating planets literally breaking up before our eyes, because of orbits close to the parent star. We have found circumbinary planets, planets that are orbiting not one, but two stars. We find planets as old as the galaxy itself; I think that was a huge surprise. It means that the raw materials for planet formation are available in the earliest stages of a galaxy’s life. We find planets associated with dead stars, orbiting white dwarfs. We also find interesting architectures: dynamically compact (planetary) systems, packed so tightly that planets feel gravitational interactions from one another.
We have learned that every star has at least one planet, and that there are tens of billions of potentially habitable, Earth-size planets. I think that latter fact has opened up a pathway for the search for life on exoplanets. Knowing there are many potentially habitable worlds catalyzes the search for life in a very tangible way.
What advice would you give a young woman seeking to enter a science or engineering field?
I always tell people just do what they love. I’m trying to remember what I told my own daughter (Natasha, now 27 and an astrophysics graduate student). There may be moments, especially in our field, which still suffers from gender imbalance, when you look around to find you’re different than most of the people sitting in the room. You’re going to have to work through that and stick it out. That’s an uncomfortable place to be. It’s going to cause you to doubt yourself. It’s important to pause and remember that you are capable and have something to offer. It is normal to find this work challenging. If you love it, persist.
One thing I’ve noticed over the years is that the students that tend to work with me on research projects are more frequently female. Not that I’m actively seeking them out; it just seems to be a natural thing that happens. To me, that highlights the need for role models. The lack of role models in the field is damaging. The expression is, “You can’t be what you can’t see.” The quickest way to close the gender gap is to provide role models.
In my undergraduate years, I never had any female professors teach my physics or astronomy classes. When I was in high school, though, I had the example of the astronaut Sally Ride. At that time, I didn’t know what I wanted to be. I went to college as a prospective business major, not a science major. When I paused and asked myself what I would do if I could do anything, the answer was to work for NASA. Immediately, that role model, Sally Ride, popped into my head.
With our own children, we were really careful (with both mom and dad working in astrophysics) not to make it astronomy 24/7 at home. In fourth grade, when our oldest daughter was 10 years old, she did a “famous American” report. She chose Sally Ride as the subject. She learned that Sally Ride was the first American woman in space and decided she wanted to be the first human on Mars. Now she’s really interested in the search for life on exoplanets. We’re sometimes even on (teleconferences) together, which is great fun.
It’s nice that Sally Ride influenced us both, and it makes me very happy to know that my own daughter will serve as a role model herself one day for future generations of explorers.
Interview by Pat Brennan, NASA’s Exoplanet Exploration Program
Last month the scientific community and the world were delighted with the announcement of a total of seven Earth-size planets orbiting a nearby star called TRAPPIST-1. Data from NASA’s Spitzer space telescope revealed the last four of these neighbors, and as planned, the Kepler space telescope also had an opportunity to look in on this interesting target.
During its observing campaign 12, covering the period of Dec. 15, 2016 to March 4, the Kepler spacecraft, operating as the K2 mission, monitored the brightness of TRAPPIST-1. Earlier this month, we released the raw, uncalibrated data to the scientific community, with the fully calibrated data to follow in the next few months. We are excited to see what these observations have added and will further contribute to the community’s investigation into the TRAPPIST-1 system.
Kepler’s K2 mission is now in its thirteenth observing campaign, monitoring a patch of sky in the direction of the constellation Taurus. During this campaign, the spacecraft will monitor more than 21,000 targets, including the Taurus star-forming region and the nearby Hyades open star cluster. Measurements of 33 galaxies, six asteroids, eight trans-Neptunian objects and one comet are also scheduled.
Over the last year, the team also has been gearing up to deliver the final data products from the Kepler [prime] mission. Today marks an important milestone: the final Kepler Object of Interest (KOI) table has been delivered and made available to the community at the NASA Exoplanet Archive. The KOI table contains a list of notable objects that show evidence of astrophysical transit events. The release of these data will help the community plan follow-up studies while our final analyses are completed. A paper detailing the mission’s final candidate catalog is anticipated this summer.
At this time of year, the original Kepler field of view rises in the night sky allowing scientists to carry out their follow-up studies of these KOIs using ground-based telescopes in the northern hemisphere.
Beginning April 1st, the Kepler/K2 guest observer office will be under the direction of Dr. Geert Barentsen. Geert will lead the team’s efforts to engage and support the broader scientific community using data from the K2 mission. He joined the team in June 2015 and has been instrumental in shaping the diverse portfolio of observation targets for the K2 mission. Geert also organized the first-of-its-kind microlensing experiment for NASA—a collaborative survey between the K2 mission and ground-based observatories around the world. Community engagement and the results of the study serve as a proof of concept for NASA’s Wide-Field Infrared Survey Telescope, to be launched in the mid-2020s. Geert is currently organizing another K2 mission campaign focused on the study of supernovae, which is scheduled to begin in December.
The spacecraft remains healthy and productive–a true explorer as it recently completed its eighth full year in space. It now trails Earth by 84 million miles in its tour around the sun. That’s about 452 light-seconds for those spatially inclined, or 0.9 AU for folks that like smaller numbers.
Kepler and K2 mission manager
NASA’s Ames Research Center
Kepler’s K2 mission is now in the midst of its eleventh campaign, observing a patch of sky in the direction of the constellation Sagittarius. During this campaign, it will observe 14,250 new targets, including the Galactic Center and Saturn’s moons Titan and Enceladus.
Campaign 11 began on Sept. 24, but was interrupted for three days (Oct. 18-20) to make a small pointing correction to accommodate the imbalance that was created by broadcasting data from a different antenna on the other side of the spacecraft. Although the spacecraft is as big and heavy as an SUV, it actually turns slightly when we change the broadcasting antenna. This is like having your car begin to turn from the force of the blinking of your turn signal. Yes, the spacecraft is that delicately balanced! Data collection for Campaign 11 will continue until Dec. 7.
Since my last update, our investigation into the cause of the spacecraft’s photometer—the onboard camera—being powered off in July during Campaign 10, confirms that that science detector Module 4 failed. The likely cause was a random part failure that resulted in a high electric current in the circuitry, which blew the protection fuse, disabling the detector but preventing the problem from propagating to other detectors. As part of the fault protection response, the photometer was powered off.
Eighteen of the 21 science detector modules remain fully operational. Two science modules had failed previously: Module 7 in January 2014 and Module 3 in January 2010. These are not unexpected events as the spacecraft ages in the harsh environment of space.
In September, the spacecraft had a unique opportunity to provide a ‘wide-angle’ view of comet 67P/Churyumov–Gerasimenko, making observations of its core and tail. These observations complement the close-in study of the comet provided by the European Space Agency’s Rosetta spacecraft during the final month of its mission. These and the remainder of Campaign 10 data have been downlinked to the ground and are being processed for release at the public archive later this month.
We’ve also made changes with the Kepler and K2 project scientist personnel.
On Sept. 6, Jessie Dotson assumed the role of project scientist for the K2 mission. Dr. Dotson was formerly the deputy science office director for Kepler and, in 2008, established the Kepler Guest Observer Office. Most recently, she served as astrophysics branch chief in the Space Science and Astrobiology Division at NASA Ames. In 2014, Jessie helped formulate the Asteroid Threat Assessment Project (ATAP) at NASA Ames to quantify the risk to Earth of an asteroid impact. She currently leads the ATAP asteroid characterization team. In 2016, Jessie was awarded a NASA Outstanding Leadership Medal for her work as the astrophysics branch chief at Ames.
Together, Natalie and Jessie replace Steve Howell who served as Kepler project scientist since 2010 and K2 project scientist since mission conception in 2013. In that role, Steve oversaw Kepler science operations through the end of its prime mission, the recovery from the reaction wheel failure that nearly ended the mission, and the development and implementation of the K2 mission that gave Kepler a new lease on life. We commend Steve for his work as the Kepler/K2 project scientist, with notable leadership in catalyzing the science community to support Kepler’s extended mission called K2.
In August, the team gathered for the annual year-in-review of spacecraft operations with Ball Aerospace, the designer, manufacturer and flight controller of Kepler. A topic of high interest is the on-board fuel reserve, which is expected to last into the spring of 2018.
At last count, Kepler has identified more than 5,100 planet candidates. Of these, more than 2,500 have been verified as bona fide planets. NASA’s next planet-hunting mission, the Transiting Exoplanet Survey Satellite (TESS), is scheduled to launch no later than June 2018. TESS will build upon Kepler’s success and search for exoplanets around the stars closest to the own solar system.
Kepler and K2 mission manager
NASA’s Ames Research Center
As reported in last week’s update, the Kepler spacecraft’s photometer—the onboard camera—was commanded to return to science after being found to be off during a routine contact on Thursday, July 28. Yesterday, the team confirmed that the photometer responded as expected and began collecting data again on Tuesday, Aug. 2.
Yesterday’s scheduled contact with the spacecraft was made using the 70-meter dish at NASA’s Deep Space Network (DSN) at Goldstone, California. The large dish provided the necessary communications link with the spacecraft to confirm Kepler was back doing science.
Our investigation of the cause centered on the focal plane detector modules. The signature of the recorded faults surrounding the anomaly was reminiscent of an event in January 2014, when one of the science detector modules (Module 7) failed. In that case, we concluded that the most likely cause was a random part failure that resulted in a high electric current in the circuitry, which blew the protection fuse, disabling the detector but preventing the problem from propagating to other detectors. As part of the fault protection response, the photometer was powered off. Thus, it seemed likely that this most recent anomaly might be the result of another random detector failure—something to be expected as we continue to extend the spacecraft’s mission.
Analysis of the temperature data from the focal plane seems to bear out this hypothesis, and points suspicion to science detector Module 4, as the likely culprit. When we turned the photometer back on, all the other modules warmed up at a consistent rate, while Module 4 reacted more slowly, and never reached full operating temperature before the DSN contact ended.
As part of our standard contact procedures yesterday, we brought down a few pixels from the focal plane to verify the precise pointing of the spacecraft, and some of these pixels were from the suspect Module 4. The data from these pixels failed to register its assigned target star, while pixels from other modules produced the expected signals from their assigned target stars. Therefore we are relatively certain that this detector has indeed failed.
For the K2 mission’s current Campaign 10, the targets that were assigned to Module 4 will yield no further science results. For the campaigns going forward, we will select targets which fall on the remaining operational detectors, which will have little to no impact to the upcoming science.
Such hardware failures were foreseen in the initial mission planning, and the system design is robust and compartmentalized to minimize the impacts. After more than seven years in the harsh conditions of space, 85 percent of Kepler’s original detectors are still operating. Module 4 will be the third of the 21 science modules to have failed in-flight.
Kepler’s primary mission ended in 2013 but exoplanet and astrophysics observations continue with the K2 mission, which began in 2014. In June, NASA Headquarters announced that Kepler is to continue science operations through the end of the FY19, by which time the on-board fuel is expected to be fully depleted.
To-date, Kepler has identified more than 5,100 planet candidates, of which 2,454 have been verified as bona fide planets. NASA’s Transiting Exoplanet Survey Satellite, scheduled to launch in 2017 or 2018, will continue Kepler’s success and search for exoplanets closer to our own solar system.
Kepler and K2 mission manager
NASA’s Ames Research Center
During a scheduled contact with NASA’s Kepler space telescope on Thursday, July 28, the team found the photometer—the camera onboard the spacecraft—powered off. The photometer was turned on again and the flight system returned to autonomous science operations on Monday, Aug. 1. We will confirm that science operations have been resumed within a week. The team is currently investigating the cause; the spacecraft is otherwise operating normally.
The Kepler spacecraft is currently in the tenth observing campaign of its second mission, called K2. Kepler’s primary mission ended in 2013 but more exoplanet and astrophysics observations continue with the K2 mission, which began in 2014. To-date, the K2 mission has identified more than 450 new planet candidates, of which 128 have been verified as bona fide planets.
In June, NASA Headquarters announced that the K2 mission is to continue science operations through the end of the FY19, by which time the on-board fuel is expected to be fully depleted.
Kepler and K2 mission manager
NASA’s Ames Research Center
The K2 mission, the two-wheel operation mode of the Kepler spacecraft observing in the ecliptic, is exhibiting no discernible ill effects since the recent Emergency Mode, other than the extra fuel usage. K2 is now in the second half of the special microlensing campaign called Campaign 9. The first half of the campaign was shortened by two weeks as a result of the emergency, and the data acquired have made public. The microlensing team has already been searching for the telltale events that indicate an object passing in front of a background star, identifying approximately two-dozen of these lensing events. Thus far, the experiment seems to be a smashing success!
While we are still dotting the i’s and crossing the t’s on the cause of the emergency, all the signs are pointing towards a single bit that changed state in the memory of an electronic chip that controls the internal command and data bus onboard the spacecraft. The memory was designed to be highly resistant to upset but if a high-energy cosmic ray hit in just the wrong place or at the wrong time in a write cycle an upset can occur. In this case, the upset caused a disruption in the internal data stream, passing invalid data sets to the flight computer, setting off several fault responses including the shutdown of critical heaters on the spacecraft. After a couple of hours, propellant froze in the propulsion system effectively disabling pointing control. Without pointing control, the spacecraft slowly drifted until the sun got too close to a “forbidden zone” around the optical axis of the telescope, causing the Emergency Mode to kick in and protect the telescope. While we have an excellent fault protection system onboard, no amount of pre-planning is going to work if we get multiple, random faults, which is why we have the Emergency Mode in the first place. And it worked beautifully!
The spacecraft emergency provided an opportunity to highlight the important role that engineering plays behind the scenes in the development and operation of a mission. Last month the engineers from NASA Ames, Ball Aerospace and the Laboratory for Atmosphere and Space Physics at the University of Colorado, both located in Boulder, who all worked on the recovery of the spacecraft, participated in a Reddit “Ask Me Anything.” The team had a fantastic time responding to the online community’s questions about the steps in the recovery and the experience of working through a high-pressure, high-visibility situation. We were encouraged by the level of interest and look forward to welcoming more problem solvers to the field of engineering. You can learn more about managing the recovery of a spacecraft 75 million miles from Earth in a recent question and answer feature.
Meanwhile the scientific results from the missions keep rolling out. Last month Dr. Timothy Morton of Princeton University announced that his analysis of the Kepler data was able to validate planethood for 1,284 more of Kepler planet candidates. The Kepler verified planet count currently stands at 2,327.
Now in its ninth observing campaign, K2 continues to produce a bounty of data for the scientific community to continue the search for exoplanets and to study planet and star formation, as well as the explosive death of red giant stars, commonly known as supernovae. The K2 planet count continues to climb, reaching more than 250 candidates, of which nearly 50 have been verified as bona fide planets.
NASA has also announced today that K2 is to continue science operations through the end of the FY19, by which time the on-board fuel is expected to be fully depleted. The mission extension, based on a recommendation from NASA’s Astrophysics Division’s 2016 Senior Review of operating missions, provides two additional years of funding for K2 to continue exoplanet discovery, and the study of notable star clusters, young and old stars, active galaxies and supernovae. For more details about the recommendation and for a listing of other missions approved for extension, see the 2016 Senior Review report.
With the emergency behind us, and fuel to last us into the summer of 2018 or beyond, the news of the two-year mission extension was a welcomed vote of confidence in the team. This news comes just a week after K2 completed two years of operations, celebrating its second “birthday.”
Kepler and K2 mission manager
NASA’s Ames Research Center
Pavel Machalek is a data scientist for the Kepler Mission. Prior to joining the team, he obtained his own funding to work on the Spitzer Space Telescope using infrared photometry to investigate Hot Jupiters, studying their temperature and structure. For Kepler, he is currently working on light curve settings for the photometer, detecting high precision photometry of Hot Jupiters as they travel behind their star. A good portion of Pavel’s day is spent troubleshooting issues, searching out possible defects in Kepler’s photometry. This work contributes to the day-to-day operation of the satellite. He and other data scientists must ensure that the data products streaming from the satellite are still valid on a bi-weekly, monthly and quarterly cycle in an iterative process to ensure that the photometer’s data runs smoothly. When necessary, he works closely with the Science Operations Center (SOC) to improve the software code and resolve issues. Pavel also helps produce documentation for both the pipeline and the public data release notes and is beginning to collaborate with the team on the Kepler scientific papers.
Meaning of the Mission
“The number one goal is to find a habitable planet, a second Earth; this mission doesn’t have the capability to discover life on an Earth-like planet, just the capability to discover a planet that lies in the habitable zone. This mission will also discover how frequently these rocky planets occur. I believe the idea of denouncing the possibility of a unique single Earth is an atheistic crusade; it is a way to fight back against religious dogmatism. It would be interesting to find out whether our Earth is the only one in the Universe or whether there are many others. In particular, it would be fascinating to contrast age-old and firmly held theological beliefs regarding the uniqueness of the Earth and our place in the Universe to the tantalizing possibility that there could be dozens, hundreds or even thousands of other worlds similar to our own.”
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.
Photometer Characterization Scientist for the Kepler Mission
A Day in the Life
Jeffrey Van Cleve spends much of his time looking at data that Kepler is about to release to MAST, the Multimission Archive at the Space Telescope Science Institute. MAST supports a variety of astronomical data archives, with a primary focus on scientifically related data sets in the optical, ultraviolet, and near-infrared parts of the spectrum. Jeff and other members of the Kepler Data Analysis Working Group (DAWG) participate in this data review in order to verify that the Kepler Science Processing Pipeline performs as expected in most cases, and to understand the exceptions. A different part of his day might be spent working on an important and interesting linear algebra puzzle to improve the Pipeline. This is one of Jeffrey’s favorite aspects of his work.
Another of Jeffrey’s tasks is working on file formats and coordinate system conventions for the MAST archive. He feels a “sense of mission that Kepler leave behind a legacy that people can use long after the mission is over to get some great science done. For example, even if almost every star system has a planet like the earth, more than 95% of Kepler’s targets will not show planets for geometrical reasons — a huge treasure trove of precise stellar light curves for astrophysical investigation. ”He and 4 or 5 other people who call themselves the FITS Fanatics work on this and though it might seem kind of dull to have lengthy discussions about file formats and header keywords, it is part of leaving behind a legacy which will make it easy for people to use and publish the data. Part of this process is to make the headers self-explanatory, so that they describe in detail how the data was collected, calibrated, and formatted.
To help with this work, two new members have been hired in the science office to work on the release notes, eventually taking over editing them and generating tables and figures. The bonus? Jeffrey will have more time to work on linear algebra puzzles!
What’s the most remarkable aspect of Kepler’s performance as an astronomical instrument? “It was the photometric precision of the CCD (visible light) sensors and the stability of the telescope pointing. It is amazing, when you think about it, that we can do 20 parts per million photometry, which requires both very stable CCDs and the ability to point the telescope to a millionth of a degree. It’s like looking at a light bulb 100 km (60 miles) away and being able to tell if a gnat is flying around it.”
Meaning of the Mission
I was curious to know what Kepler’s existence means to Jeffrey on a personal level. “The prevalence of habitable worlds, as measured by Kepler, helps us assess the probability of finding intelligence in other star systems in our Galaxy. What I really appreciate about Kepler is that it allows me to contribute to an optimistic vision of the human future, one that includes colonizing planets in other star systems, or communicating with intelligent species that have survived the perils we currently face. Their existence alone would be a beacon of hope.”
To read Jeffrey Van Cleve’s full biography, click here.