Gaps in the Data
I wanted to give a brief update on the gap question and talk a little more about what causes those gaps in the data.
You might have noticed that the gap question is no more. All of the lightcurve sections from Quarter 2 have breaks of varying sizes in them which was not the case for the Q1 data, so we removed the gap question from the interface yesterday. The gaps are caused by a few different things: Kepler went into safe mode and wasn’t taking data, the spacecraft was rotating towards the Earth, the spacecraft has executing a roll (or quarterly roll as its called) to reorient its solar panels, or the data is bad either due to a cosmic ray hit or something else.
The spacecraft rolls and safe mode tend to make of the majority of the data breaks. Kepler must rotate towards Earth to send its science data on timescales of approximately 30 days. During those monthly data downlinks Kepler must point away from the field and point its antenna towards the Earth to send the 150,000 lightcurves of data collected to the science operations center via NASA’s Deep Space Network. Every few months, the spacecraft must also reposition its solar panels toward the Sun and point Kepler’s radiator into deep space with a quarter turn, which causes an additional gap of about 1 day in the lightcurves. The reason we don’t see any gaps in the Q1 data (about 35 days) is because it encompasses one downlink of data, but since Q2 is 90 days there is both the quarterly and month rolls.
I’m off to Kitt Peak for an observing run to observe a transit in our own solar system. Dwarf planet Huamea’s moon (Nemaka) is passing in front of Haumea Friday night and I’ll be attempting to observe the drop in light caused by Nemaka on the WIYN telescope (3.5 m) while my collaborators will be observing the event from the Hale Telescope (200 inch) at Palomar Observatory.
Happy Hunting,
PS. I also wanted to say thank you for everyone’s patience and understanding while we’ve sorted out the Q2 data upload and the Talk links.They should hopefully be done late tonight early tomorrow
Looking for Gems in Talk
I wanted to talk a bit more about the Talk collections. There is a treasure trove of information sitting in all of the unique and interesting collections you are all making in Talk. We made our first list of planet candidates using the classifications you’ve all made in the classify interface (see John’s post). We want to start digging into your great Talk collections and find the interesting gems in there.
We have a visiting student from France, Thibault Sartori from École normale supérieure. One of his projects is going to be taking a look at all the great Talk collections you made. He will be looking for interesting transits, small radii-planets, and multi-planet system that may not be extracted from the classify interface. If you have a collection of interesting transits or potentially new multi-planet systems, we’d like if you can add a #phtransits (for single planet systems) and #phmulti (if you have collections of multiplanet systems) to your collections. We’ll search the Talk database for collections with these keywords and extract their entries after Sunday.
We’re also willing to feature a collection on the Talk page, so if you have something cool you want the rest of the community to see or what help with adding new objects, tweet, email, or post it on facebook and we’ll feature the collection on the front page. We can’t wait to see what’s in your collections, and we’ll keep you posted on Thibault’s progress and what we find on the blog.
Happy Hunting,
PS. I was observing in Chile at La Silla two weeks ago, and wanted to share some pictures of the telescopes. I was using the NTT the kinda of squarish telescope in the back left which has the clouds behind it
Q2 Data Release and Site Upgrades
We wanted to talk more about the changes to the site and give you all an update on the addition of Quarter 2 data. John’s already talked about the candidates page and some of the new features associated with that, so I wanted to focus on the changes specific to Q2 data release.
NASA and the Kepler team released Quarter 2 on Feb 1st and on Feb 2nd the latest results from the Kepler mission including a complete list of planet candidates and false positives for the first 2 quarters of data. You can read the paper detailing all of this here as well as the Kepler press conference site
The second data release is 90 days so we now have the first approximately 120 days of the Kepler science mission to go through. Q1 was about 35 days, we have chosen to show chunks of the lightcurve in the same size as we were for Q1. So Q2 is broken into three sections. Our aim was to have 5 days worth of overlap in each section, so that we don’t miss any transits that happen at the starts and ends of where we separated the lightcurves. We’re also uploading the Q1 data from the ~400 stars originally withheld and released on Feb 1st. We’ll keep you all posted on the progress.
We have been uploading the new data in batches to make the transition as smooth and seamless as possible. Occasionally the Talk links lag behind because we’re trying to upload as fast as you’re all going through the data. And sometimes you beat us to it
so we’ve increased how fast we’re uploading the Q2 data to keep up with your pace. We’ve appreciated all your patience during this process.
You can tell which part of the lightcurve you are looking at by the APH#. The first two numbers are quarter and section so APH22332480 is section 2 of Quarter 2. We use APH for the lightcurve sections and SPH for referring to the star itself. For the SPH numbers the first two numbers refer to what quarter the star first appeared in the public data set. so SPH21332480 first appeared is Quarter 2 Section 1.
The star source pages (like http://www.planethunters.org/sources/SPH10129795) contain all the sections of lightcurve for you to review and the x-axis is the days from the first observation, so you can look for repeat transits in other sections of the lightcurve easily. Also the downloadable CSV file now contains all the available lightcurve data. We have also updated the gap question (the first question asked) in the classify interface, so now you will now be asked the variability questions regardless of how your answer the gap question (before the variability questions were skipped if you answered yes to their being a data glitch or gap in the lightcurve)
We’ve made some changes to Talk to accommodate the Q2 data. The new planet candidates list and false positive list from the Kepler team are now identified. We’re planning in the near future of marking Planet Hunters planet candidates as well. Each lightcurve section has it’s own object page (ie http://talk.planethunters.org/objects/APH22332480). We now have group pages that gather all the available lightcurve object pages for the star (http://talk.planethunters.org/groups/SPH21332480) which you can access through the “View Star” link on any of the object pages. The “Examine Star” link will take you directly to the star’s source page.
As always we welcome feedback on the new changes, and we are listening to your comments and suggestions on Talk and in your emails. We can’t wait to see what we find in the Quarter 2 data.
Happy Hunting,
Candidate Selection
Hello there planet hunters, John here again. We know that you have been anxiously awaiting word on all of the transits you have been detecting. The first batch of stars with promising transits has been released today and I wanted to give you an overview of how we selected these particular stars out of the ones you marked.
We started with the 1.2 million classifications you made between December 15th and January 16th. Any star which had a transit marked by at least 5 people and had not previously been published was our first cut. That left us with 3533 stars.
We then had a small team of astronomers here at Yale quickly go through and rate these on a 5 point scale as likely planets and eclipsing binaries. A sort of Hot-or-Not for transits. We were now down to about 800 stars that fell into one or both of those categories.
Finally, three senior dip spotters went more carefully through this list, rating them again. Any star which was marked as either a possible planet or eclipsing binary with a score of 4 or better made it onto this first list of candidates. 90 possible planets and 42 possible eclipsing binaries!
There were many exciting transits that did not make the cut. Mostly it was because we need more data. You will notice that there are some single transits in the list, but there were just so many good ones it was hard to leave them out.
Our next step is to model these transits and weed out any more that may look promising by eye but aren’t quite as regular as they appear. This will also allow us to add radius and period information for most of the stars. Additionally, we will be including all of those stars where you identified existing planets, planet candidates, and eclipsing binaries from published works. I can already tell you that you easily found all of the published confirmed Kepler planets which were in the data.
So, head on over to the Candidates pages, or check out the two new links on your profile page which shows you any planet or eclipsing binary candidates which you marked a transit on.
Thanks for all of the hard work!
John M. Brewer
Candidates and Upgrades
Hello everyone, graduate student John here. The time has finally arrived and we have the first batch of candidates up for you. To top it off, we have also managed some interface updates which should make marking transits faster and easier (yeah, Stuart!).
First, the candidates. I have a blog post coming out shortly which will explain how we made our selections so for now I will just give you the results. If you roll on over to the Candidates page, you will find that there are 132 new stars. That breaks down into 90 new potential planet candidates and 42 potential eclipsing binaries. We are still hard at work modeling these systems, so don’t have much more information than that it made the cut. We thought you would rather see them now and we will add the periods and radii as we do the fits.
Along with the new candidates, you can now see stars which you viewed which are possible planet or eclipsing binary candidates.
Which brings us to the other interface updates: transit marking. Now when you want to mark a transit on a star, you can simply drag a box around all of the points in the transit. Once drawn, the boxes work exactly as they did before. This should help us get more precise transit center information to more easily track down interesting candidates. Another perk is that clicking on any of the transit boxes will zoom you to that location on the plot.
Bring on the new data!
John M. Brewer
New Kepler Data: Feb 1
By Zak Kaplan (Yale undergrad)
Planet Hunters has just completed its first analysis of the Kepler data! With your classifications, we were able to extract information about all of the 150,000 light curves. We would like to thank the more than 16,000 registered users who have helped make Planet Hunters such a success. Special thanks to the collectors and the top 14 users who each analyzed over 5000 light curves, accounting for over 10% of the 1.3 million classifications.
To give a better idea of what you’re measuring in a transit curve, a planet crossing a star causes about the same dimming of light as a small fruit fly passing in front of a car headlight. Now imagine that car is a few thousand light-years away, and you get a sense of just how amazing the Kepler data and your work have been.
The Kepler team will have a press conference on 2 February 2011, announcing their new candidates and releasing new data that will more than quadruple the amount of data that we can serve to you. You can join the live broadcast on NASA TV at 1pm EST and we will post the Kepler press release here next Wednesday.
For the past week, the Exoplanet Research Team at Yale has been analyzing over 3500 light curves that you marked with promising transits. We found that PH users marked transits that we would have missed. From this first set of data, we have culled approximately 300 strong planet candidates, as well as several new eclipsing binary star systems. We are formatting the new Candidates pages now so that they will appear before the Kepler press conference. Then, you can check to see which objects you detected independently, before the Kepler team announced them. It will be especially interesting to see if there are some good candidates that you all found that are not on their new list. If so, we will ask the Kepler team for feedback on your new candidates.
We hope you will help continue to prove the power of citizen science, as we look for more planets beyond our solar system. Until then, keep on hunting!
Talk Updates
Our two new community collaboration websites, Milky Way Talk and Planet Hunters Talk, had some updates this week. We thought it was worth going over them in this blog post. We’ve had a lot of feedback about Talk and are working to implement the most-requested features.
The biggest difference you’ll see when logging into Talk is that your discussions are now easier to manage and track. A new, large box on the main page shows all the new and updated discussions since your last login. You can refine these using the two drop-down boxes at the top of this section. You can chose to show discussions from the last 24 hours, the last week, or since any date using a pop-up calendar. You can also chose to only see discussions that you are a part of, which should help you keep track of your conversations.
In addition to these changes, you’ll also find a lot more metadata around the discussions, telling you who last posted, how many people are taking part, and who started the discussion, where relevant. Users within these discussions are now highlighted if they are part of the development team or the science team. This is something a lot of you asked for.
The other item that has been changed with this Talk update is pagination. There are now easy-to-use buttons on the discussions, collections and objects on the front page. These mean that you can browse back through time and see more than just the most recent items. As Talk has grown more popular, this feature has become more necessary.
Another change to the front page is that we now show the most-recent items by default, and not the trending items. You can still see the trending items by clicking the link at the top. Users told us they preferred to see recent activity initially so we made the change. Similarly, the ‘trending keywords’ list now appears on the front page at all times.
On Planet Hunters Talk, when you’re viewing a light curve, Kepler Planet Candidates are now identified as a “Kepler Favorite”.
Finally, page titles are now meaningful. This means that if you bookmark or share a link, you’ll remember why. Collections are named and objects will be title dusing their Zooniverse ID (e.g. APH….). Several of you have also noted our lack of a favicon (the little icon next to the URL in your browser bar). This is coming shortly as well.
There are more changes planned for Talk, but these significant updates to the front page were worth noting on the blog. For example, we plan to start integrating social media links into the Talk sites, along with more updates as time goes by. Talk continues to evolve and we welcome feedback. Post comments and suggestions on the Feature Requests Thread or Board Upgrades thread on Talk or send us an email at team@planethunters.org.
Downloading the Data
We’ve rolled out a new feature to the site. You now have the ability to download the lightcurve data directly from Planet Hunters. Once you’ve classified a star and submitted the transits, the download data button will appear and is available for every star on its source page (ie http://www.planethunters.org/sources/SPH10067557) as well as from the user My Star page (http://www.planethunters.org/profile) where you can download the data for all the stars you’ve classified (we’ve now paginated the My Stars page so all your favorites and all the stars you’ve classified should now be listed).
The file is in CSV (Comma-Separated Values) format which can be opened directly or imported into Excel, Numbers or the Open Office equivalent where you can then plot and manipulate the data. We provide additional info about the star properties including infrared color, specific gravity, right ascension and declination, and Kepler IDs. We also identify if the star is a Simulation (simulated transit lightcurve), a Kepler Planet Candidate (ie Kepler Favorite -a star that the Kepler team believes has a transiting planet but has not confirmed with follow-up observations) or Source (real Kepler lightcurve). For the simulated lightcurves, the CSV file will provide the planet radius in Earth radii and orbital period in days for the injected transit signal (assuming the given radius of the star).
The CSV file also contains three columns of data labeled time (days), brightness, error in brightness. The brightness values are the brightness of the star measured by Kepler per observation corrected for instrumental effects and systematic errors by the Kepler Team’s data processing pipeline. The error in brightness is simply +/- error in the reported brightness measurement. We’ve normalized the brightness values by dividing what we get from the Kepler public release data by a constant value just for convenience, so it’s easier to measure relative change in the brightness of the star. This just shifts the absolute value of the y-axis up or down for our plotted lightcurves but doesn’t change the actual depths of any transits. For more specifics about the data, see the Corrected Light Curves section of http://keplergo.arc.nasa.gov/DataAnalysisProducts.shtml.
Some times there’s a missing data point in the lightcurves the Kepler Team has released. These missing data points indicate a”no data” condition where the observation has been compromised by spacecraft operations or other anomalies that effect the quality of the measurements (examples might be the spacecraft entering safe mode or possibly a glitch with the electronics that readout for the flux measurements for that star). To indicate those data points we’ve set the brightness value to zero in the CSV file.
Happy Hunting,
More star info…
Thanks again for your amazing work and feedback. We are working to keep up with you! There is now a data-download button (thanks to Chris, Arfon, Michael, and Stuart!) on the star pages. We are also integrating information about stars that are known eclipsing binaries (EB), Kepler planet candidates (PC) and false positives (FP). Here is an ascii list of light curves with this information. On this list, the APH number is given, followed by the Kepler ID and a flag (EB, PC, FP). For EB objects, D indicates detached binaries, SD is semi-detached, OC is an overcontact binary. Kepler PC stars include columns with the prospective period and planet radius (in Jupiter radii units).
One note about false positives: There are light curves that masquerade as transiting planets. For example, light from a bright foreground star is spread out over several pixels on the CCD detector. The halo of starlight is swept up into a single brightness measurement by the Kepler team’s software. However, in some cases a more distant eclipsing binary (EB) star system blends into the edges of the foreground star. Since the EB is more distant, it is fainter and contributes a smaller fraction of the light. In this case, the background eclipse produces a diluted signal that looks very much like a transiting planet. There are a couple of ways to eliminate these imposters:
- the Kepler team has software that looks for pixel contamination and identifies the star as a false positive (FP). When available, we are listing this information on the light curve and star pages.
- Follow up radial velocity measurements of the bright star will also include the background blended eclipsing binary. A large velocity signal can be a give away sign that the light curve does not arise from a transiting planet.
This follow-up is a critical effort, required to move an object from a transit candidate to a planet.
Simulated Transits
In this blog post, we wanted to focus on the simulated transits you’ve been seeing and why they’re important to the project, as well as answer some of the questions regarding them.
One of the goal of Planet Hunters is to explore the diversity of the terrestrial and giant planet populations and begin to understand the spectrum of solar systems providing crucial context for own solar system. How many Jupiter sized planets are out there? How many Neptune-sized? How many Earth-sized? are solar systems like ours common? These questions are fundamental to understanding how planets form and evolve.
With just the planet discoveries alone you can’t answer these questions because you don’t know how complete the sample is. This is because you don’t know how sensitive to detecting planets of different types the project is, particularly since this is a new way to look for planets that has never been done before. If we found one earth-sized planet for example. We can’t say anything about their abundance compared to gas giant planets, since we don’t know how many we might have missed in the data set -that’s where the simulated transits come in.
We added Kepler lightcurves into the PH interface with simulated transits, spanning the range of exoplanet radii and orbital periods, to test which kinds of transiting planets can be detected with Planet Hunters to assess the fraction of missed planets. If users flag 100% of the Jupiter-sized planets with orbital periods shorter than 30 days, but only 50% of the Neptune-size planets with orbital periods shorter than 30 days, then we know that the number of transiting Neptunes in the real light curves is a factor of two larger than what has been flagged. This provides a powerful statement about the fraction of transiting planets that could only be made with the Planet Hunter collective.
It might seem like we’re testing you or trying to train you to identify transits , but we’re really testing the project. This is a really vital part of the project, with these simulated transits we can answer these really interesting and fundamental questions about how solar systems and planets form.
Some of the simulated planets like large Jupiter-sized planets will be really easy to spot while others will be near impossible to identify especially for the extremely small planets, but don’t be discouraged if you didn’t find the simulated transit. That’s okay, that’s part of the experiment. We don’t know what Planet Hunters we will be able to detect so we have to look at the look at range of possible planet radii and orbits. Can we find 1.2 Earth radii planets? 1.6? and how does incompleteness change in this critical range of radius? How much worse does detectability get when there is just 1 transit instead of 3?- with the simulated transits we will be able to answer these questions. With this information we can then start putting a picture together of the abundance and variety of solar systems.
We will always identify the simulated transit points in red after you’ve classified the star and will mark the lightcurve as simulated data in Talk. The reason we don’t identify the simulated data first, is that if you knew the lightcurve had simulated events you might look at it differently. To be able to use the data from the simulated transits accurately, we need them to be examined in exactly the same conditions as the real lightcurves.
Users on PH Talk have said that for some of the simulated transits the red points are in the wrong spot. The points we are marking for the simulated transits are correct. There are two reasons why it might look like the points are wrong
- The lightcurve have really a small and distat planet injected, and the flux drop caused by this planet would be so small it doesn’t look any different than the normal lightcurve. Right now we’re working to display the radius and period of the simulated transit signal injected, once you’ve classified it, so you can identify this for yourself.
- The star is an eclipsing binary or already has a transit signal from a larger planet than the one we injected into the lightcurve, since we don’t know beforehand which of the lightcurves in the Kepler data set have transiting planets or stars. These simulated events and your classifications for them are still useful because it gives us estimates for multiplanet system and how sensitive we could detect an additional transiting planet.
We know there were a few glitches we needed to work out with the simulated lightcurves that were making them conspicuous, we’ve fixed those, and the zoom works for the simulated lightcurves. We’ve also dialed back how frequently a user will see a simulated lightcurve. We’ll post some examples of the simulated transits in the next blog post.
Happy Hunting,
Planet Hunters 