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
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,
Eclipsing Binaries
Figure 1. Eclipsing Binary (detached, Algol type)
I’m Debra Fischer, a Professor of Astronomy at Yale University. Many of you have already discovered some amazing eclipsing binary light curves, and we wanted to provide you with some information. The Figures here show examples that you have put into collections. Some great additional examples are shown in a paper from the Kepler team (Prsá et al. 2010 http://arxiv.org/abs/1006.2815).
The Kepler light curves show how the brightness of the star changes with time. In Figure 1 (APH10135736 = KID 6449358) above, there are two stars orbiting each other. Similar to transiting planets, these stars cross in front of each other. The light curve shows the brightness level of the star, plotted vs time in days. Most of the time, both the larger, hotter star and the smaller cooler star yield a combined brightness measurement for the light curve. When the deep dip in brightness (the primary minimum) occurs it’s because the smaller cooler star is eclipsing the hotter star, which contributes most of the light; when the smaller dip (secondary minimum) occurs, it’s because the larger hotter star is eclipsing the smaller star, which contributes less light to the combined brightness. Stars with flat regions punctuated by relatively sharp dips (e.g. Figure 1) are known as Algol binaries.
A key indicator of eclipsing (or transiting planet) light curves is repeatability.
- you can count the number of days between the large dips to determine the orbital period (about 5 days) of this binary star system in Figure 1
- you can determine how long it takes the stars to cross by the duration of the transit dip (hours for Figure 1)
- you know that one star is larger than the other if the transits don’t have equal dips
Notice that the depth of the brightness dips for an eclipsing binary star can be similar to those for a transiting planet. The transit depth tells us the ratio of the size of the transiting (or eclipsing) object relative to the size of the primary star and the smallest stars have diameters that are similar to Jupiter (stars are gas and the increased gravity from the larger mass star compresses the structure).
Figure 2. Contact eclipsing binary stars
Sometimes binary stars are so close that the surfaces are distorted into an elliptical shape and the light curve between the eclipses is rounded, as in the left image of Figure 2 (APH10039007 = KID 9357275), where the orbital period is a little more than one day. You can see both the primary and secondary transit dip in this light curve. The most bizarre eclipsing binary light curves are those where the stars are even closer together, called over-contact binaries. An example of this is shown in the right image of Figure 2 (APH10102932 = KID 4633285). These stars can be so close together that they share a common envelope. The eclipse depth is variable, the light curve looks irregular, and there can be mass transfer between the stars.
Stellar Variability
Greetings from Kevin Schawinski and Meg Schwamb, postdoctoral fellows at Yale and members of the Science Team.
Wow, we’ve been blown away by how enthusiastic everyone has been about the project. In this post, we wanted to talk more about another goal of Planet Hunters, which is to study and better understand stellar variability. The public release Kepler data set is unprecedented, both in observing cadence and in the photometric precision. The lightcurves reveal subtle variability that has never before been documented.
The Kepler lightcurves are complex many exhibiting significant structure including multiple oscillations imposed on top of each other as well as short-lived variations. Most of this variability is due by starspots or stellar pulsations.With Planet Hunters we will not only be looking for stars harboring planets outside of our solar system, but we will be able to study and classify stellar variability in ways that automated routines cannot. Unlike a machine learning approach, human classifiers recognize the unusual and have a remarkable ability to recognize archetypes and assemble groups of similar objects.
Users have the ability to identify strange or unusual lightcurves as well as tag similar curves and come up with their own classes or ”collections” of variability with Planet Hunters Talk. You can add a comment and use the #hashtag like in Twitter to mark an interesting lightcurve and alert others including the science team. Every light curve, or collection of curves has a short-message thread (140 characters) associated with it for general comments. You also can start discussions if you want to chat in a more in-depth fashion.
Mining the Kepler data set will inevitably lead to unexpected discoveries, showcased by the successes of Galaxy Zoo. The prime examples are the discoveries of ”Hanny’s Voorwerp” and the ”green peas” by Galaxy Zoo users. Hanny’s Voorwerp is a cloud of ionized gas in the Sloan Digital Sky Survey image of the nearby galaxy IC 2497. Unlike an automatic classification routine, citizen scientist Hanny van Arkel spotted a blue smudge next to IC 2497, recognized it as unusual, and alerted the Galaxy Zoo team and the other users. Since then, Hanny’s Voorwerp has been identified as a light echo from a recent quasar phase in IC 2497, making it the Rosetta Stone of quasars. The Galaxy Zoo participants started noticing a very rare class of objects of point sources showed as green in the SDSS color scheme. Dubbing them the ”green peas,” the citizen scientists scoured the SDSS database, and assembled a list of these ”pea galaxies.” The ”peas” were revealed to be ultra-compact, powerful starburst galaxies whose properties are highly unusual in the present day universe, but resemble those of primordial galaxies in the early universe. The citizen scientists found veritable fossils living in the present-day universe.
With so many eyes looking at the lightcurves, we are bound to find new variability types! We’re hoping that Planet Hunters, like Galaxy Zoo, will yield exciting new results that we can’t even attempt to speculate or imagine! We can’t wait to see what turns up.
Planet Hunters Introduction
Hi, I’m Meg Schwamb a postdoctoral fellow at Yale University and member of the Planet Hunters Team. Welcome to Planet Hunters! We’ve been working hard, and we are excited to finally show you the finished product!
In the last decade, we have seen an explosion in the number of known planets orbiting stars beyond our own solar system. With ground based transit searches, stellar radial-velocity observations, and microlensing detections, over 500 extrasolar planets (exoplanets) have been discovered to date. Studying the physical and dynamical properties of each of these new worlds has revolutionized our understanding of planetary formation and the evolution of planetary systems. But we have just barely scratched the surface in understanding the diversity of planetary systems and planet formation pathways.The current inventory of known exoplanets has been limited to mostly Jupiter-sized or larger gas-rich planets, most orbiting extremely close to their parent stars. The current inventory of known exoplanets has been limited to mostly Jupiter-sized or larger gas-rich planets, most orbiting extremely close to their parent stars. While these planets have provided great insight into the formation of giant planets, beyond Mercury, Venus, Earth, and Mars, in our own solar system, little is known about the formation and prevalence of rocky terrestrial planets in the universe.
Finding Earth-size planets is a difficult task because the transit-signals, the dimming of the star’s light caused be a planet moving in front of the star, are so shallow. For a Jupiter-size planet, the transit depth is ~1% of the star’s brightness. For an Earth-size planet transiting a Sun-like star the decrease in brightness is less than .001%. Ground-based surveys have not reached the sensitivity to detect such planets around stars similar to our Sun, but with NASA’s space-based Kepler mission, launched in March 2009, astronomers are primed to start a new era in the study of exoplanets. Even with the exceptional data from the Kepler telescope, finding these Earth-sized planets will be extremely difficult, but in the age of Kepler, the first rocky planets will likely be detected including the potential to find Earth-like planets residing in the habitable zone, warm enough to harbor liquid water and potentially life on their surfaces.
NASA’s Kepler spacecraft is one of the most powerful tools in the hunt for extrasolar planets. The Kepler data set is unprecedented, both in observing cadence and in the photometric precision. Before Kepler, the only star monitored this precisely was our own Sun. The lightcurves reveal subtle variability that has never before been documented. The Kepler data set is a unique reservoir waiting to be tapped. Kepler lightcurves are now publicly available with the first data release this past June and the next release scheduled for February 2011.
The Kepler Team computers are sifting through the data, but we at Planet Hunters are betting that there will be transit signals which can only be found via the remarkable human ability for pattern recognition. Computers are only good at finding what they’ve been taught to look for. Whereas the human brain has the uncanny ability to recognize patterns and immediately pick out what is strange or unique, far beyond what we can teach machines to do. With Planet Hunters we are looking for the needle in the haystack, and ask you to help us search for planets.
This is a gamble, a bet, if you will, on the ability of humans to beat machines just occasionally. It may be that no new planets are found or that computers have the job down to a fine art. That’s ok. For science to progress sometimes we have to do experiments, and although it may not seem like it at the time negative results are as valuable as positive ones. Most of the lightcurves will be flat devoid of transit signals but yet, it’s just possible that you might be the first to know that a star somewhere out there in the Milky Way has a companion, just as our Sun does.
Fancy giving it a try?
Planet Hunters 