Kepler vs. TESS

Kepler and TESS are both amazing space telescopes that have and will revolutionise our understanding of exoplanets. But let’s have a look at how these two telescopes differ?


Artist impression of NASA’s planet-hunting Kepler spacecraft (left) and TESS satellite (right). Image credit: NASA Ames/JPL-Caltech/T Pyle

Kepler was launched in March 2009 and used a 1.4-m primary mirror that observed a 12×12 degree patch of sky (for reference the Moon covers half a degree on the sky). The sensitivity of Kepler was significantly better than that of any other instruments at the time, thus enabling Kepler to find exoplanets as small as half the size of the Earth.

Conversely, TESS will survey the entire sky, looking at 400 times more stars than Kepler did throughout its lifetime. TESS will do this with four identical telescopes, which, combined, observe a 24-degree patch of sky at any one point. Each 27 days, TESS changes direction and looks for planets around a different set of stars in a new ‘sector’. The entire sky has been split into 26 overlapping sectors, and TESS will visit each one over the course of the next 2 years.


The combined field of view of the four TESS cameras (left) and the sub-division of the celestial sphere into 26 observation sectors (right). Image credit: NASA 

The two satellites also differ in their observing strategy and the types of stars that they focus on. Whilst Kepler observed one patch of sky for a long period of time, TESS will only spend a month looking at each sector. The long exposure times of Kepler allowed it to find the dimmer and more distant stars, whereas TESS will monitor the nearby, and brightest targets. In fact, the stars observed by TESS are 10 times closer and 100 times brighter than the Kepler target stars! Observing brighter and closer stars has the advantage that any planet candidates that we find will be easier to observe using ground based telescopes.


Artist impression of a burning exoplanet. Image credit: NASA 

The main Kepler mission ended in 2013, when the telescope lost its ability to change orientation without the use of fuel. Luckily, engineers and astronomers quickly realised that the pressure from the Sun could be used to steer the telescope in order to keep it pointing at one patch of the sky. This new era of observations became known as the K2 mission.

K2 ran out of fuel in mid 2018, bringing the mission to a close. Luckily, by this point NASA’s new satellite TESS had already been launched. We now have brightness measurements of around 45,000 stars from the first three sectors, and we are already finding some promising planet candidates within the TESS data!

Will you help us find the planets hidden within the TESS data? Click here to give it a go!





More TESS Data and More Planets Waiting to be Found

Planet Hunters TESS is back with brand new data!  The Sector 3 lightcurves have just been released and we are ready to find the planets hidden within them. This new data set consists of brightness measurements of 16 thousand bright stars that were observed by TESS between 22 September to 17 October, 2018.


Artists impression of a Distant Alien World. Photocredit: Nora Eisner

You may notice some difference between this data release and the last one. During the Sector 3 observations TESS underwent some test in order to improve the data quality. This meant that the data collected during the first four and the last three days of the scheduled observations are not usable, leaving us with around 21 days, as opposed to the usual 28 days, of data. These tests are necessary as they give the amazing TESS system engineers and scientist the opportunity to learn more about how the satellite operates, allowing them to advance the system and improve the pointing stability. Due to this the TESS data will improve with every new sector. Each 21 day lightcurve has been split into three sections, providing you with higher resolution data and making it easier to spot even the smallest dips in brightness.

There are sure to be many planets hidden within this data, ranging from Earth-sized rocky planets to Jupiter-like gas giants orbiting around various different types of stars. What kind of planet will you find?

We hope you enjoy the new TESS data. Happy Planet Hunting!

Data Reduction Guide

Think you’ve found a great transit candidate? Can’t wait for us researchers to look into it? Here are a few things that you can do yourself to check whether your candidate could be a real planet. These are the first steps that we would do ourselves, so it’s a great help to us if you have the time or inclination to make a start yourself – and a great opportunity to learn a few cool things in the process. Note you can do as many or as few of the steps on this list as you like – it’s completely up to you!

1. Is it a TOI (Tess Object of Interest)?

TOI is the name used by the TESS team for good planet candidates that they have checked carefully and consider worthy of follow-up observations.


In order to check whether the candidate is a TOI you need to find the TIC number (you can view it by clicking the “i” icon below the subject image in Talk) and check if it appears on the TESS data alerts page: TIC ID is the first column in the big table. If the candidate is on the TOI list, well done – you have found a candidate that the TESS team have identified as a planet candidate.


If the candidate you found is a TOI you’re doing really well. However, it’s already being looked into by the TESS team, so we won’t duplicate their efforts – we want to focus on objects that they haven’t already found. Before you leave the talk page for that subject though, please tell everyone else what you’ve found – you can say “This is Tess Object of Interest (TOI) XXX” where XXX is the number that appears in the 2nd column on the data alerts table.

2. Is it a TCE (Threshold Crossing Event)?

All of the TESS data are passed through the TESS transit search pipeline, which automatically flags any lightcurves that might contain a planet. TCEs are the raw flagged candidates of this pipeline (prior to any vetting done by the TESS team).

In order to check whether a candidate is a TCE you can download a CSV file, for each sector, where they are all listed:

Alternatively you can check if a given candidate is a TCE using EXOMAST ( On EXOMAST, simply enter “TIC ” followed by the TIC number, and click ‘search’. If the candidate you are looking into is a TCE, you will  be taken to a page containing some information about the host star and the potential planetary system.


If the candidate is not a TCE, you will see a notification below the search bar stating “No planet found”.


If you find a TCE, once again, you’re doing really well – it means that you’re as good at finding (some) transits as the pipeline that professional astronomers developed over a number of years!

Please flag such an object as a #TCE on the talk page (if possible including a link to the EXOMAST page for that TCE).

3. It’s a TCE but not TOI?

A candidate that is a TCE but not a TOI is an object that the TESS pipeline flagged, but the TESS team decided wasn’t a good enough planet candidate to be promoted to TOI status. Finding these is really great, not least because – in some cases – we might take a different view to the TESS team and consider them to be likely planet candidates. So if you find a TCE that isn’t a TOI, please let us know by including “@researchers” in your comment on talk. We will get notified automatically and – time permitting – we will look at it more closely.

When vetting the TCEs, the TESS team perform a long list of checks. These tests are designed to weed out instrumental false positive (the signal isn’t real) and astrophysical false positives (the signal is real but isn’t caused by a planet, but something else). The results of these tests are saved in a DV (data validation) report, which they have helpfully made publicly available – so we can use them to understand why the TCE didn’t become a TOI. This is a really quick way to look through candidates and to avoid repeating the hard work that the TESS team have already done. The DV reports are long and complex, and currently a little tricky to access for TCEs that aren’t TOIs, so we are not including instructions on downloading and using DV reports in this post (though we hope to do so at a later date).

Importantly, there are already a few TCE (and not TOI) candidates found by volunteers for which we have examined the DV reports and come to the conclusion that the candidates are promising. This mainly happens because the TESS pipeline requires at least two transits for a detection, so it only searches for transits that repeat with periods up to the duration of a TESS sector (~28 days). If there is only one real transit, it might be missed altogether (this is where you volunteers come in!) or it might be wrongly paired up with an artefact or noise feature somewhere else in the light curve. In that case, the diagnostics in the DV report, which are based on all the transits combined, might be misleading.

4. Create a cutout or movie of the TESS data

There is a fun tool at which allows you to extract a time-series of cutout images around a given target. You can use these to look at what is in the vicinity of the target, or even to make a movie! If the transit is deep enough, you might even see the star “blink” (this can be a fun thing to try out on variable stars or eclipsing binaries too).


Sometimes, what appears to look like a transit is actually due to some weird artefacts, affectionately dubbed “fireflies” or “fireworks” by the TESS team, that sweep through the field of view. These are probably due to scattered light from bright stars or moving objects inside the telescope and camera optics. If you notice that a promising candidate is actually due to such an artefact, please let everyone know on talk!

5. Want to play with the TESS data products yourself?


If you’re really keen and want to examine the TESS data in more detail, you can easily get your hands on them. Go to, enter “TIC” followed by the TIC number of the subject in the search box, and hit “search“. This should bring up a list of datasets stored by MAST (Mikulski Archive for Space Telescopes), including two that will have “TESS” in the “Project” column. The lightcurve is the one that lists the TIC number (rather than “TESS FFI”) under “Target name”.


You can download the data to your computer by clicking on the little floppy disk icon in the corresponding row. You can find more information on the format of these datasets in the TESS Science Data Products Description Document:

What to do with the data when you have it is a long story, far too long for this post… but again, we hope to provide a separate, dedicated article with some examples at a later date.

Initial Planet Candidates

Thank you so much for all your amazing work! The next data release is just around the corner so hopefully everyone is ready to find some more planets. Until then, we have some preliminary results from the sector one data.

Over the past month the science team has been working hard on putting together a list of some of the most promising planet candidates. We find these by carefully looking at the lightcurves where many of you marked planets in the same location. With a careful eye we filter out lightcurves that show eclipsing binaries or that have transit-like events due to systematic effects. We  can identify these by looking at features such as the shape and depth of the dips, as well as the time of the transit.

The candidates that withstand this initial filtering process have to go through a further screening before they can be promoted to be a high priority planet candidate. This screening involves looking at the variability of nearby stars, the depths of the alternating transits (if the lightcurve shows multiple transits), and stellar parameter of the host star.

So far, we have identified five high priority candidates, three of which are TCEs (you can see their lightcurves below). Even though these lightcurves have passed all of our tests up to this point, we cannot confirm that these transits are due to planets without further observations. As a next step we will, therefore, look to observe these targets with ground based telescopes in order to find out more about these fascinating systems.

image from ios

We are very excited about these initial five candidates and look forward to finding many more as we finish looking through the sector one data. Stay tuned for more results!

Planet Hunters TESS

Welcome to our new Planet Hunters TESS project!

TESS is NASA’s new Transiting Exoplanet Survey Satellite, which will spend the next two years looking for distant alien worlds. The first batch of data has only just been released by NASA and we are ready to find planets around other stars in our Galaxy. Will you join the search?

We are proudly following in the footsteps of the tremendously successful Planet Hunters project. You may have heard of this project, or even contributed to some of its amazing discoveries. Over the course of eight years they found over two-thousand planet candidates, including planetary systems that we didn’t even think possible!

The original Planet Hunters project used data from the Kepler mission, which came to an end earlier this year. But with the end of Kepler comes the beginning of TESS, NASA’s Transiting Exoplanet Survey Satellite, and with that an exciting new project: Planet Hunters TESS. Throughout the mission, TESS will point its four cameras at two-hundred-thousand bright nearby stars, four-hundred times more than Kepler observed throughout its lifetime. These TESS target stars will be closer and brighter than the Kepler targets, which will allow us to more easily observe planet candidates using Earth-based telescopes. The discovery of many more worlds will further our knowledge of planet formation and evolution, and will allow us to better understand the galaxy in which we live.

But we can’t find them alone! We’ll be hunting for planets by monitoring the light given off by a star. When an planet passes, or “transits”, in front of its host star, the star momentarily dims and we see a dip in the light. This method of detecting planets has already proven to be extremely effective! Even though we can train machines to find some planets, studies have shown that human brains are excellent at detecting patterns and finding planets that automated routines miss. Together we can find the most complex, unusual and exciting planetary systems.

We’re the new Planet Hunters TESS core science team, and we’re very excited to have you join our hunt for distant worlds at

We hope you enjoy the project!

Nora & the Planet Hunters TESS team

Planet Hunters: a new beginning!

In 2010, the Planet Hunters website began showing light curves from the Kepler mission to Citizen Scientist volunteers. This project was different from other Zooniverse projects like the successful “Galaxy Zoo” because instead of showing beautiful images, we were serving up “boring graphs” of brightness measurements for 150,000 stars.
• Would people be interested in spending time sifting through these data to find changes in brightness from transiting planets?
• Would humans beat out the sophisticated computer algorithms designed by NASA scientists?
• Would Planet Hunter volunteers contribute unique scientific discoveries that would otherwise be undiscovered today?

We now know the answers to these questions: yes, yes and yes! In retrospect, the right question would have been: can the scientists keep up with the wave of discoveries from Planet Hunter volunteers? Barely!

Planet Hunters has been a game-changer and showcases the ability of Citizen Scientists to make important discoveries. Here are some highlights of the ways that you have changed our understanding of exoplanets:
1. Planet Hunters independently identified about 2000 of the planets found by the NASA Kepler team.
2. Excluding cases where a discovery was also made by science teams working on the Kepler data, Planet Hunters uniquely contributed 120 unique discoveries that would otherwise still be buried in the Kepler data today. For transiting planets with orbits longer than 2 years, Planet Hunters detected 50% of the planets that are known today.
3. You identified hundreds of eclipsing binary stars, and most surprising, planets orbiting outside of eclipsing binary systems! Who knew that these objects could even exist? …you found them!
4. You identified the most mysterious star in the galaxy: “Tabby’s Star,” which gained notoriety when Jason Wright at Penn State suggested that this could be the sign of an alien megastructure. We did not promote that intriguing explanation, but Tabby Boyajian gave an amazing TED talk about this discovery and has an ongoing campaign to study that star.

This scientific legacy could not have happened without the many, many hours that all of you put into this project. Your patient and persistent clicks on prospective transit events have changed our understanding of exoplanets. Thank you for your hard work!  We also owe a debt of thanks to the dedicated Zooniverse team, the postdocs, grad students and undergrads who worked tirelessly on Planet Hunters!

Over the past 8 years, we became friends. We chatted through the Talk site, met each other at Kepler meetings and our most active users wrote data analysis tools and helped to guide new volunteers. Many of you were co-authors on Planet Hunter discovery papers. In 2012, Planet Hunter Kian Jek won the American Astronomical Society Chambliss prize for “achievement in astronomical research by an amateur astronomer.” In 2016, that prize was awarded to Daryll LaCourse. In 2017, we were saddened by the passing of Gerald Green, a co-author on science papers and one our most active volunteers. In May 2018, Smith College students Rebekah and Jennifer Kahn, who became interested in astronomy while volunteering as high school students, arrived at Yale to work on summer research, modeling of the Kepler-150 system.

Now, it’s time for a transition – a new beginning for Planet Hunters. There will be a new look and feel to the website, and the light curves will come from the NASA TESS mission (launched in April 2018), instead of Kepler. We need you more than ever and hope that you’ll continue with the search for transiting exoplanets and other weird things in the galaxy!

“ I wanted to contribute to the world of planetary science in a meaningful way”

-an interview with Al Schmitt by Jennifer and Rebekah Kahn

Al Schmitt is a long-time Planet Hunters member. Having lived during the space program era and been an avid follower of subsequent space missions, Al found that Planet Hunters enabled him to actively participate in planetary science research. In fact, he used his job experience as a software engineer to develop LcTools, a light curve display and signal analysis toolset designed specifically for the Planet Hunters community. Al is also a researcher on the HEK team “The Hunt for Exomoons with Kepler” whose goal is to determine the occurrence rate of exomoons. Al has co-authored many published research papers in association with Planet Hunters and the HEK project. We thought that it would be of interest to other fellow Planet Hunters members to learn more about LcTools and how Al is able to pursue his passion as a citizen scientist.

You can learn more about LcTools on his website:
More Information on the HEK project can be viewed here:

PH: Would you tell us a bit about your background?
AS: Career wise, I was a software engineer for 35 years developing applications in various engineering fields including computer diagnostics, computer aided design (integrated circuits and printed circuit boards), and medical software (heart pacemakers and defibrillators). In 2010, I retired early in part to pursue science on an amateur basis.

PH: When did you first become interested in Astronomy?
AS: I grew up in the 1950s and 1960s closely following our manned space program which I found extremely exciting. Planetary science became more important starting in the mid-1970s with the Viking missions to Mars. My interest in planetary science continued to grow with the Galileo and Cassini missions. As I approached retirement, I knew that I wanted to contribute to the world of planetary science in a meaningful way.

PH: Is this why you joined Planet Hunters?
AS: Yes. I joined in April 2011 a few months after the website became fully operational. Over the next couple of months, I spent a great deal of time classifying stars and identifying transit candidates. This was a big learning period for me since I didn’t have any prior experience in this area.

PH: How did you become involved with the HEK project and the search for exomoons?
AS: In June 2011, Gerald Green started a thread in the PH science forum for discussing potential moon and ring signals seen in Kepler lightcurves. I joined the discussion and quickly decided that exomoon research would be my new focus area. At about the same time, I read a research paper by David Kipping which showed model exomoon signals based on his LUNA algorithm. Armed with this knowledge, I performed my own visual exomoon survey for several hundred KOIs and then sent him the results. A few months later, David asked me to join his new research project called HEK – The Hunt for Exomoons with Kepler.

PH: Was your work on the HEK project related to your development of LcTools?
AS: Very much so. LcTools was born out of necessity. I needed a software tool to perform large-scale visual surveys of Kepler lightcurves in a fast and efficient manner with the ability to record candidate signals of any type. In early 2012, I developed an application called LcViewer to accomplish this. LcViewer formed the basis for a much larger system of applications called LcTools developed over the next six years.

PH: What are the other applications in LcTools?
AS: In addition to LcViewer, there are five other major applications. LcSignalFinder automatically detects and records periodic signals found in a set of lightcurve files. LcGenerator builds lightcurve files in bulk for use by LcViewer and LcSignalFinder. LcReporter generates an Excel spreadsheet showing all the user defined signals recorded by LcViewer. The last two applications in the system are LcStacker and LcStackAnalyzer.
LcTools is described in detail on my website. The website also includes links to Kepler and K2 lightcurves designed to work with LcViewer and LcSignalFinder. Over 200,000 files are available for the Kepler project and about 350,000 files for the K2 project.

PH: Can LcTools be used by other individuals?
AS: Indeed it can. Initially I built the system for myself but I quickly realized that it could be extremely useful to other serious researchers especially those with a strong science, technology, or astronomy background (LcTools is not designed for entry level users). Currently, I have 63 registered users spanning the citizen science, academic, and professional domains.

PH: What are some of the notable highlights of LcTools?
AS: First and foremost, the system is designed to be fast and easy to use. Operation is simplified wherever possible. The system is optimized for high volume processing of lightcurves.
Second, the system supports signals of any type whether astrophysical in origin or not. Signals may be periodic, quasi-periodic, or non-periodic. This permits a wide range of phenomena to be studied.
Third, signals can be imported into LcViewer and LcSignalFinder from various external sources when a lightcurve file is loaded. For example, project based signals such as KOIs, K2OIs, and TCEs can be imported from the NASA Exoplanet Archive. Signals can also be imported from public signal libraries designed to be shared between individuals or groups across the network via shared Google Drive folders. Use of public signal libraries opens the door to collaborative research projects. Fourth, the system supports a comprehensive set of high-level features typically found in professional lightcurve analysis packages. Major features include detrending of lightcurves, automatic detection of periodic signals, and phase folding of periodic signals.

PH: What new features are planned for LcTools?
AS: The most important upcoming feature is support for the TESS project. My goal is to have a product ready for customers shortly after MAST releases the first batch of lightcurves to the public hopefully sometime in November or December. The high volume capabilities of LcTools will be essential for handling the large number of lightcurves expected.

PH: You are listed as co-author on a number of research papers. Which one do you consider most significant and why?
AS: The most significant would be the last HEK paper published a year ago. In it, we mention a strong exomoon candidate dubbed KOI-1625b I. Over the past eight months, David Kipping and Alex Teachey have been very busy vetting the candidate (I have not been part of this effort since it’s well outside my field of expertise). If the candidate can pass all of the vetting tests, then we will have discovered the first confirmed exomoon. Such a discovery would usher in a new era of research, similar to what the first confirmed exoplanet did back in the mid-1990s.

PH: What advice would you give veteran PH citizen scientists moving forward?
AS: Don’t be afraid to investigate new phenomena! Kepler and K2 lightcurves may be host to a wide variety of intriguing phenomena such as moons, rings, trojans, and comets. By no means has everything been found! There are important discoveries still to be made if you’re willing to search.
Thank you Al for discussing your personal involvement with research in the field of Planetary Science.  We are excited to see what the new release of LcTools will entail, and hope that your experience in this field will also inspire other citizen scientists.

The Launch of TESS and Planet Hunters!

Congratulations to the NASA TESS team for a successful launch! This is an exciting new start for transiting exoplanet discoveries and it also signals a new start for Planet Hunters! We are looking forward to showing TESS data on our site in the coming months.

You may have noticed that things have been quiet on the Planet Hunter site recently. The team of postdocs and grad students working on Planet Hunters have inevitably moved on to new positions. However, behind the scenes, we are working on the M dwarf planet occurrence rates based on your classifications. We are working with the Zooniverse team to move Planet Hunters to a more robust new platform. And we have reached out to several of our citizen scientists for ideas about how to move forward with Planet Hunters. This summer, Rebekah and Jennifer Kahn will be working on Planet Hunters at Yale. They will be setting up a site with light curve fitting tools developed by and for Planet Hunters and preparing for the TESS data.

Some interesting statistics about Planet Hunters:

  • We have had more than 500,000 volunteers on our site. These citizen scientists have classified millions of light curves, contributing a cumulative total of almost 200 years (the 24/7 classification time for a single person working 200 years non-stop).
  • Planet Hunters has been supported by Yale University, grants from NASA, and gifts in memory of Jerry Green. We are working on a new grant proposal to NASA to support a postdoctoral fellow who will provide strong leadership on the Planet Hunter site.
  • Two of our citizen scientists (Kian Jek and Daryll LaCourse) were awarded the Chambliss prize for amateur astronomy from the American Astronomical Society.
  • One PhD thesis (by Joey Schmidt) was based on Planet Hunters.

Watch this space – we’re excited about the new changes ahead!

“Without Planet Hunters, none of the subsequent discoveries would have been possible.”

An interview with PH Tom Jacobs, by Rebekah and Jennifer Kahn

Thomas Lee Jacobs is a long-time Planet Hunters member who recently coauthored “Likely Transiting Exocomets Detected by Kepler,” a paper in which the first exocomets were discovered by the transit method through his persevering efforts in reviewing over 200,000 light curves.  Published in Monthly Notices of the Royal Astronomical Society, you can read that paper here: . This is not Tom’s first scholarly paper, having previously been listed as coauthor of nine other papers, in which he explored eclipsing binaries, long period exoplanet orbits, and Jupiter size exoplanets in the Habitable Zone. And he tells us “there are more in the works.”  With such a record of scholarly accomplishments as a citizen scientist, we thought his views of the past, present and future of PH would be worth listening to.  And yes, he is a real citizen scientist; having graduated with a non-science degree from the University of Washington in Business Administration, his rewarding day job is working as an employment consultant for workers with intellectual disabilities.

PH: Could you tell us what attracted you to Planet Hunters when it was founded seven years ago?  Were you already an amateur astronomer?  Had you already been involved in exoplanets, and what other astronomy interests did you have then or now?

TJ: I originally was drawn to citizen science projects created by the Zooniverse Citizen Science Alliance at MoonZoo and moved over to Planet Hunters when it was launched in December of 2010. The idea of looking for planets outside of our solar system when there was only a handful of known exoplanet discoveries at the time was intriguing. We all know now that the NASA Kepler space telescope has revolutionized astronomy and astrophysics, but at the launch of Planet Hunters there were many unknowns. I think back to that period of time as being similar to the “Wild West”, as everything was fresh and uncharted and little was known about what we would find together as Planet Hunters members. For me, I started at ground zero with no background in astronomy and my college major was in business not science.

PH: What has been your experience with Planet Hunters, then and now?

TJ: As mentioned, I became a member of Planet Hunters around 2010 and attended the first Kepler Science Conference in 2011. At Planet Hunters “Talk” I began learning from other members with more experience and insight into the light curves. Kian Jek (kianjin) was one of the most respected members at the time. There were many stalwart surveyors and contributors and I list only a few- Gerald Green, Hans Martin Schwengeler, Daryll LaCourse, Alan Schmitt, Troy Winarski, Mark Omohundro, Johann Sejpka, Ivan Terentev and Robert Gagliano. What they all have in common is dedication, perseverance and a great love for finding new and unusual events in the light curves. Kian, Daryll and I attended the first Kepler Science Conference in 2011. At that time, Planet Hunters was very novel to the astronomical community. Non-science folks, making meaningful discoveries by visual survey of the Kepler data, still had a ways to go to being acceptable in science papers. Of course, this has all changed as we fast forward to today and Planet Hunters has made significant discoveries. It is safe to say that without Planet Hunters coming on to the scene, some of the more unusual astrophysical discoveries would still remain dormant in the Kepler data. Just think of Boyajian’s star, KIC 8462852.

If you do not have an advanced mathematical and science background do not worry. I do not have one either and can only perform the most basic analysis of the Kepler light curves. What I do have is the treasure hunter zeal and a practiced eye that lends well for surveying and looking for unusual patterns in the data. Currently, I survey the Kepler K2 data using Alan Schmitt’s LcTools light curve viewer and work in collaboration with Daryll and two veteran astronomers, Saul Rappaport and Andrew Vanderburg. Daryll and I perform the initial identification and screening and Saul and Andrew do all the heavy lifting (analysis).  I have since been a coauthor on 10 Kepler science papers with more in the works.

PH: What were some of the early obstacles that PH had to overcome?

TJ: I think you both will agree that the original concept and design for Planet Hunters using crowd-sourcing techniques to identify interesting events quickly became obsolete. Some obstacles for analysis were not having access to the real KIC nomenclature, access to the Kepler data and having a fast, high resolution light curve viewer showing the entire observation period. This resulted in an independent subsystem of light curve analysis and sharing in the Planet Hunters “Talk” section.

PH: Well, we can remember that, at the time, things were moving along rather rapidly and everyone in the exoplanet community was learning on the fly.

TJ: One has to also acknowledge that in 2010 this was all new territory and the learning curve evolved over time. Without Planet Hunters, none of the subsequent discoveries would have been possible.

PH: And individual Planet Hunters not only made these discoveries, but also developed the analytical tools that enabled them.  Can you tell us about that?

TJ: Yes. As you know, Alan Schmitt’s LcTools program was created to address the shortfall I mentioned of not having a fast, high resolution light curve viewer.  His programs now provide a complete set of analytical tools. One can quickly scan individual light curves in ten seconds or less (actually an almost instantaneous scrolling feature) with excellent light curve resolution.

This year, I generated the Kepler DR25 long cadence light curves and they are available on his site, linked to my Gmail Google Drive as zip files for the LcTools viewer.

PH: Well, we hope to interview Mr. Schmitt for PH in the future and learn more from his perspective also.  Now, you have been a significant force in making many PH discoveries.   What particular outlook do you bring to the search for other worlds and how does this align with the PH mission and exoplanetary discovery as a whole?

TJ: I would consider myself more of a Kepler pattern recognition treasure hunter veteran and an individual who can perform only the most basic light curve analysis. I leave the heavy lifting to the skilled veterans.

PH: But you have been a coauthor on several important papers and part of so many exoplanet discoveries.  Surely there is a bit more to it?

TJ: There are some tools available online for a more detailed look and many planet hunters are adept in doing so. I am not one of them. What I have found is over the course of many years one can develop an eye for what is an interesting event and what may be simply noise or artifacts in the light curves. Though periodicity is a key tell for real astrophysical events, machine searches are well suited to beat the trained citizen scientist making visual surveys. However, single (less so now), aperiodic and new light curve patterns of real astrophysical events give the visual surveyor a real edge in this area.

PH: So, even in these new days of neural networks and machine ‘deep learning’ that characterize light curves with great accuracy, there is still a place for citizen scientists and Planet Hunters?

TJ: A machine will only find known patterns. The visual surveyor travels into uncharted areas finding new and unusual events.

PH: Such as your recent exocomets find, for sure!  Well, what is your process for finding and analyzing light curves and what resources do you use?

TJ: When I survey a light curve, the first thing I do is look for unusual or known light curve patterns. Depending on how they appear will give the surveyor an idea if the events are real, the star owns the events, if there are third body events and/or if there is contamination. The next thing to check is the actual FOV. PanSTARRS is relatively new site though there are others:

I will not list all the K2 and Kepler main field online archives search sites as they are well known. The IRSA/WISE site is also a great resource of looking for WISE band 4 IR that is a great tell for “Dippers.”  Of course, Andrew Vanderburg’s site is a must see for K2. He has a page for each K2 light curve that shows background contamination such as BGEBs:

PH: What future projects do you think PH should pursue? And what are some suggestions for improvement?

TJ: I would be interested in learning more about how Planet Hunters will be working with the new TESS data when it becomes operational later this year (hopefully).   Educating and training its members to work more independently and developing close relationships with veteran science team members with timely feedback would be of significant help.  There will be quite a bit of excellent data to analyze and citizen scientists will need strong advocates in the professional astronomical community to ensure the data is accessible to the public similar to the Kepler data, though I have been told that the data will be accessible similar to K2.

PH: Can you point to any particular discoveries or experiences over the last seven years that you particularly enjoyed or are especially proud of?

In January of last year, I took on a very large project of downloading and visually surveying all 201,250 light curves of the Kepler prime-field stars in Ames Data Release 25. Alan Schmitt and I collaborated in downloading the stars. This was a dream that I had envisioned while surveying at Planet Hunters. What until January was not in place to do this was the technology, team, experience and time. The survey took five months and I kind of went off the charts devoting most of my free time to visually surveying before and after my day job working as a Special Projects manager for AtWork! in Bellevue, Washington helping people with intellectual disabilities find paid employment in their community. I have been doing this rewarding work for over 21 years. The visual survey was completed in May and a rich harvest of interesting finds was discovered. The discovery that stands out and is likely my high-water mark for surveying is the exocomet paper recently published last fall. These are the first exocomet candidates ever discovered using transit photometry. Without the team effort, the comets would still be lurking in the Kepler data. That is the power of visually surveying, team effort and a love of finding new and usual things in the light curves. Thank you Planet Hunters and Happy Hunting!

Thank you, Tom.  We appreciate your work, explanation of your outlook and methods, and recommendations for the future. In particular, we hope that your thoughts might stimulate some further discussion on this blog.  Reminiscences of our successful past are welcome, but practical suggestions for our future would be truly exciting.

It all began with Planet Hunters

Here is a great Planet Hunters story from Rebekah and Jennifer Kahn.

My sister and I are spending an entire week listening to and speaking with some of the top researchers of exoplanets. There, among the names of such renowned scientists as Batalha, Borucki, and Charbonneau from NASA and large universities, are Jennifer and Rebekah Kahn, undergraduates from small, all-women’s Smith College – registered participants! And as we take part in the international Kepler & K2 Science Conference, we think about how we got here and know that it all began with Planet Hunters.

Twin sisters born in China, we came to America when we were adopted at one year old, growing up on our eastern Connecticut farm, loving baseball, decorating the Revolutionary War graves just beyond our stone walls, and learning the constellations so brightly visible in our beautifully dark night sky. We were normal, healthy kids, except for our teeth. We each had two major dental operations in our very first years’ home and probably hold a world’s record in orthodontics, wearing braces from age 8 to age 17. All this required very frequent trips to specialized dentists in New Haven and Yale. Our dad, trying to make those visits educational if not enjoyable, each time took us to another Yale museum, library, or exhibit. The planetarium and observatory were our favorites (or second favorites, next to the collection of harpsichords that we were actually allowed to play). We became regulars there, looking through the telescopes, seeing each new show and exhibit, and gratefully receiving gift books from Heidi, the administrator.

It was a cold, clear January night in 2011 when the Yale astronomer assisting in observing asked us if we would be interested in becoming part of a new research project called Planet Hunters. A research project? Open to kids? We were ready the moment he asked. The chance to do “real” science and not just study it was exactly what we wanted – but of course, as we learned, first we had to do a bit more studying. You see, at age 14, like so many other people, we had never heard of exoplanets. While we had read science fiction stories, we did not know that 51 Pegasi B had made them a reality. So, Planet Hunters taught us about transits and light curves, and that led to transit depths, which then led to M dwarfs and the different star types, which in turn led to the Hertzsprung-Russell diagram, and then the effects of starspots and even eclipsing binaries. Taking part in Planet Hunters was not just our first chance to be “real” scientists (who were convinced that we would be the first to find another Earth), but also an immensely instructive project that made our education as painlessly distracting as our father had hoped our Yale visits would be. While we were too shy to participate in the on-line discussions, we read them avidly and learned much. Two years went by and, as home-schooled high schoolers still entranced by exoplanets, we were accepted into a distance learning “Computational Astrophysics” course from Dr. Laura Trouille (now a co-PI of Zooniverse) of Northwestern University, which published our term project Towards Eta sub Earth. Then as college freshman we spent the summer working on the Wesleyan Transiting Exoplanet Project for Prof. Seth Redfield, resulting in a paper on exoplanet light curves from white dwarfs, published by the Keck Astronomy Consortium.

And now, as undergraduate sophomores, here we are at NASA Ames Research Center. Jennifer is working with Dr. Jack Lissauer on discovering how varying the eccentricity of uniformly-spaced earth-sized planets in a Hamiltonian system affects the long-term stability of a planetary system, using the symplectic integrator REBOUND.  The aim is to examine the nature of planetary system formation over long periods of time.  Rebekah is working with Dr. Mark Marley looking at simulated data sets of exoplanet brightness to be obtained by the WFIRST Space Telescope with filter photometry; analyzing the brightness of each planet, and determining how much can be learned from photometry without spectra. The goal is to enable successful exoplanet characterization without a spectrometer flying on WFIRST, due to budget constraints.  We are both exercising our programming knowledge at the moment, modeling the processes and then varying the inputs to better understand the results.  We will be developing posters for later presentation and possibly short papers.  It is challenging and interesting work and we are doing a lot of late night reading to make sure we get it right.

Back at the conference we note that there are a significant number of talks discussing the pipeline and processing of Kepler data. Basic difficulties of SNR and PSF have led to applying advanced methods such as MCMC and ROBOVET. Yet all of these are simply designed to improve the extraction of light curves with less error; all are attempting to decide whether the data indicates an exoplanet or an artifact. That is exactly what we were, and are, all trying to do at Planet Hunters.
If imitation is the sincerest form of flattery, then the talk by Prof. Ian Crossfield on crowd-sourcing K2 data interpretation through his “Exoplanet Explorers” project is very high praise for Planet Hunters, which it so closely resembles. While we ourselves have not been active Hunters for a while, we are proud to be part of a project which has enabled citizens to make important discoveries with published papers, two Chambliss Award winners (we haven’t run into Daryll LaCourse who is supposed to be at this conference), and even gained some popular fame (or perhaps notoriety) through the possibility of aliens revealed in Tabby’s Star.

To be honest, we are not “natural” STEM scholars and sometimes think we should be pursuing our harpsichord studies rather than exoplanet research. We struggle with the concepts and work long hours to make clear our research goals, but the importance of the quest outweighs our challenges in pursuing it. While we didn’t discover Earth 2.0 when we were 14, we truly believe that we will be part of that discovery in our lifetime. And, for us, it all began with Planet Hunters.