In the blog post earlier today, I reported that phase 1 was complete – the IAU (International Astronomical Union) has selected the stars to be named. Phase 2 involves groups providing naming suggestions for the star and all attached planets. The “Vote” button has been updated with a new form to begin taking these suggestions from Planet Hunters! Please provide your naming suggestion by April 16, 2015.
After April 16, 2015, the Planet Hunter’s moderators will review the suggestions for conformance to the stated guidelines for naming suggestions and a poll will be set up for us to select our one naming suggestion that will be put up. So start your suggesting!
Proposed names should be:
- 16 characters or less in length.
- Preferably one word.
- Pronounceable (in some language)
- Not too similar to an existing name of an astronomical object. Names already assigned to astronomical objects can be checked using the links http://cds.u-strasbg.fr/cgi-bin/sesame (for galactic and extragalactic names), and the MPC database http://www.minorplanetcenter.net/db_search (for names)
In addition it is not allowed to propose:
- Names of pet animals.
- Names of a purely or principally commercial nature.
- Names of individuals, places or events principally known for political, military or religious activities.
- Names of living individuals.
- Only names that are not protected by trademarks or other forms of intellectual property claims may be proposed.
As you are likely aware, Planet Hunters is taking part in an IAU (International Astronomical Union) project to name several ExoWorlds. A few months back we provided the IAU a list of ExoWorlds which we thought should be named. The IAU took this list, plus all of the lists provided by other groups and determined which ExoWorlds will be named. In total, 15 stars and 32 planets will be named. The list:
|Host Star (catalogue)||# Planet (designation)||Planet Mass (Jupiter mass)||Planet Mass (Earth mass)||Orbital Period (day)||Semi Major Axis (au)||Discovery (year)||Constellation (English)||Visibility||V magnitude|
|1 exoplanet (5 systems)|
|Ain (epsilon Tauri)||epsilon Tauri b||7.6||2415.5||594.9||1.93||2007||the Bull||Visible to the naked eye||3.5|
|Edasich (iota Draconis)||iota Draconis b||8.82||2803.3||510.7||1.275||2002||the Dragon||Visible to the naked eye||3.3|
|Errai (gamma Cephei)||gamma Cephei b||1.85||588||903.3||2.05||2003||the King||Visible to the naked eye||3.2|
|Fomalhaut (alpha Piscis Austrini)||Fomalhaut b||3||953.5||320000||115||2008||the Southern Fish||Visible to the naked eye||1.2|
|Pollux (beta Geminorum)||beta Geminorum b||2.9||921.7||589.64||1.69||2006||the Twins||Visible to the naked eye||1.2|
|1 star + 1 exoplanet (10 systems)|
|14 Andromedae||14 Andromedae b||5.33||1694||185.84||0.83||2008||the Chained Maiden||Visible to the naked eye||5.2|
|18 Delphinis||18 Delphinis b||10.3||3273.6||993.3||2.6||2008||the Dolphin||Faint to the naked eye||5.5|
|42 Draconis||42 Draconis b||3.88||1233.2||479.1||1.19||2008||the Dragon||Visible to the naked eye||4.8|
|51 Pegasi||51 Pegasi b||0.47||148.7||4.23||0.052||1995||the Winged Horse||Visible to the naked eye||5.5|
|epsilon Eridani||epsilon Eridani b||1.55||492.6||2502||3.39||2000||the River||Visible to the naked eye||3.7|
|HD 104985||HD 104985 b||6.3||2002.3||198.2||0.78||2003||the Giraffe||Faint to the naked eye||5.8|
|HD 149026||HD 149026 b||0.36||113.1||2.88||0.04288||2005||the Hercules||Visible through binocular||8.2|
|HD 81688||HD 81688 b||2.7||858.1||184.02||0.81||2008||the Great Bear||Visible to the naked eye||5.4|
|ksi Aquilae||ksi Aquilae b||2.8||889.9||136.75||0.68||2008||the Eagle||Visible to the naked eye||4.7|
|tau Bootis||tau Bootis b||5.9||1875.2||3.31||0.046||1996||the Herdsman||Visible to the naked eye||4.5|
|1 star + 2 exoplanets (1 system)|
47 Ursae Majoris
|47 Ursae Majoris b||2.53||804.1||1078||2.1||1996||the Great Bear||Visible to the naked eye||5.1|
|47 Ursae Majoris c||0.54||171.6||2391||3.6||2001||the Great Bear||Visible to the naked eye||5.1|
|1 star + 3 exoplanets (2 systems)|
PSR 1257 12
|PSR 1257 12 b||7.00E-05||0.022||25.26||0.19||1992||the Maiden|
|PSR 1257 12 c||0.01||4.1||66.54||0.36||1992||the Maiden|
|PSR 1257 12 d||0.01||3.8||98.21||0.46||1992||the Maiden|
|upsilon Andromedae b||0.62||197.1||4.62||0.059||1996||the Chained Maiden||Visible to the naked eye||4.1|
|upsilon Andromedae c||1.8||572.1||237.7||0.861||1999||the Chained Maiden||Visible to the naked eye||4.1|
|upsilon Andromedae d||10.19||3238.7||1302.61||2.55||1999||the Chained Maiden||Visible to the naked eye||4.1|
|1 star + 4 exoplanets (1 system)|
|mu Arae b||1.68||532.7||643.25||1.5||2000||the Altar||Visible to the naked eye||5.2|
|mu Arae c||0.03||10.6||9.64||0.09094||2004||the Altar||Visible to the naked eye||5.2|
|mu Arae d||0.52||165.9||310.55||0.921||2004||the Altar||Visible to the naked eye||5.2|
|mu Arae e||1.81||576.5||4205.8||5.235||2006||the Altar||Visible to the naked eye||5.2|
|1 star + 5 exoplanets (1 system)|
|55 Cancri b||0.8||254.3||14.65||0.1134||1996||the Crab||Faint to the naked eye||6|
|55 Cancri c||0.17||53.7||44.34||0.2403||2002||the Crab||Faint to the naked eye||6|
|55 Cancri d||3.84||1218.9||5218||5.76||2002||the Crab||Faint to the naked eye||6|
|55 Cancri e||0.03||8.3||0.74||0.0156||2004||the Crab||Faint to the naked eye||6|
|55 Cancri f||0.14||45.8||260.7||0.781||2007||the Crab||Faint to the naked eye||6|
At this point, Planet Hunters can submit one naming suggestion. A suggestion consists of the name for one star, all attached planets and the basis for this recommendation. We are working to set up a Google form to select submissions and then we will have a round of voting to select the candidate to be submitted. This will all take place prior to May 31, 2015.
A new MAST High Level Science Product from K2 has been delivered that includes extracted lightcurves. Courtesy of Vanderburg & Johnson (2014), long-cadence targets from Campaigns 0 and 1 now have detrended, extracted lightcurves available at MAST, including 20 different photometric apertures. There’s a MAST Classic Search Interface so you can get lightcurves based on target IDs, coordinates, EPIC catalog fluxes, etc. You can also use our interactive plotter to explore the lightcurves using any of the photometric apertures before downloading the FITS files. Check out all the details here: http://archive.stsci.edu/prepds/k2sff/
This is exciting! The International Astronomical Union (IAU) is working Zooniverse, astronomical clubs and the public at large to name some number of exoworlds and host stars. Some of the work has already been done, some work is yet to do. The exciting part is that Planet Hunters will be assisting in some of the next steps! Let’s break down their milestones:
- July 2014: IAU compiled a list of 305 exoworlds confirmed prior to December 31, 2008 as candidates for naming.
- October 2014: The IAU opened http://www.nameexoworlds.org to permit astronomy organizations to register to take part. Planet Hunters completed this and was confirmed!
- January 2015: Planet Hunters, along with other clubs, will vote for the ExoWorlds they wish to name out of the list provided by the IAU.
- February 2015: Planet Hunters, along with other clubs, will send in proposals for the names of members of these selected ExoWorlds (including the host star), based on the rules in the IAU Exoplanet Naming Theme, together with a detailed supporting argument for their choice. Each group is allowed to name only one ExoWorld. More details on this stage will be given later.
- June 2015: the general public votes to rank the proposed names.
- July 2015: the IAU, via its Executive Committee Working Group on the Public Naming of Planets and Planetary Satellites, oversees the final stages of the contest, and validates the winning names from the vote.
- 3–14 August 2015: the results are announced at a special public ceremony held during the IAU XXIX General Assembly in Honolulu, USA
We are in the January 2015 milestone. You may have noticed that there is a new “Vote” button on the Planet Hunters classification ribbon. This button takes you to a poll which has been set up to collect Planet Hunter community input. We want your participation! So let’s name an ExoWorld!!!
Today we have a post by Andrew Vanderburg. Andrew is a graduate student at Harvard University who works on producing and correcting K2 light curves and searching them for planets. He recently joined the Planet Hunters team to provide K2 light curves for classification.
As readers of this blog are probably well aware, the K2 mission is an exciting new opportunity for the Kepler spacecraft to continue searching for exoplanets, even after the failure of two reaction wheels ended the original Kepler mission. Making K2 work is in several ways more complicated than Kepler, and previous posts have already discussed how Kepler is stabilized by balancing against solar radiation and pointing itself opposite the sun in the ecliptic plane. Even with this very clever strategy for data collection, getting high quality data from K2 is not straightforward.
Once it became clear in early 2014 that Kepler would be able to continue gathering data, one of the biggest uncertainties about the K2 mission was: “How well can Kepler measure photometry in this new operating mode?” If Kepler’s worsened ability to point itself degrades the quality of its data, it may be harder for the K2 mission to accomplish its goals of finding exoplanets in new environments and around different types of stars. When the Kepler team released data from a 9 day engineering test of the new operation mode taken in February 2014, we attempted to answer that question.
After four years of being spoiled by ultra-high-quality photometry from Kepler, our first look at the K2 data came as a bit of a shock. Unlike the pristine Kepler data, K2 data (shown compared to Kepler in the first image) had wild jagged features contaminating the light curve, which made it hard to see all but the deepest planet transits. In order to continue searching for small planets in the K2 mission, something would have to be done to improve the quality of the photometry.
We started out by trying to figure out what was causing the jagged features in K2 data. Since nothing had changed with the spacecraft other than the reaction wheel failure, it was a pretty good bet that the jagged noise was due to the decreased stability of the spacecraft. We checked to see if this was the case by measuring the apparently position of stars in the images Kepler took (shown in the second image), and comparing them to the measured brightness.
The top panel shows the brightness of one particular star called EPIC 60021426 over the course of a week of the engineering test, and the bottom two panels show the horizontal and vertical position of the star, as seen by Kepler, over the same time period. It turns out that just like a cell phone video taken by a person with shaky hands, the images Kepler took were jittering back and forth. And more importantly, the jagged pattern in the location of the star in the image looked very much like the pattern seen in the brightness data.
We concluded that the additional noise in the data was caused by Kepler moving back and forth ever so slightly as it rolled due to a slight imbalance between the spacecraft and the Solar wind. Every six hours or so, Kepler’s thrusters fired to bring the telescope back to its original position. But the most important thing we concluded was that the additional noise in K2 data is very predictable. If the noise is predictable, then it’s correctable.
The third image shows the brightness of a particular star (once again, EPIC 60021426) measured by K2 on the vertical axis, and the position of the star on the horizontal axis. The blue dots indicate brightness measurements during normal K2 operations, and they form a tight relation with the image position. The jagged noise in K2 data depends only on where the image falls on the Kepler camera. With this realization, it’s simple to draw a line through the points (the orange line in the image), and divide it away. The red points are points taken while Kepler’s thrusters were firing, and don’t fit the pattern of the rest of the points. We simply throw them out.
After dividing the orange line from the data and removing points taken during thruster fires, we are left with a “corrected” light curve. The fourth image shows the result of the correction. The top light curve (blue) shows the raw, uncorrected K2 data, and the bottom, orange light curve shows the corrected K2 data. The correction substantially improves the quality of the K2 data.
This type of processing improves the precision of K2 to where it’s close to that of Kepler — within a factor of two for most stars. This makes it possible to detect small planets, even when the planetary signals are much smaller than the jagged variations removed by this process. We discovered the first K2 exoplanet, HIP 116454, using this exact technique, and the one transit we found was totally obscured in the raw K2 data (as shown in the fifth image).
Even now, however, this process is not perfect, and we’re still working to make it better. There are quite frequently glitches and other errors that affect the light curves and make it difficult for computer algorithms to pick out all of the transit signals. Trained human eyes like yours will be crucial for picking out all of the exciting exoplanets that K2 will observe.
Now that were in the midst of the showing the first batch of science grade data from the K2 mission, I thought I’d give some more details about the K2 light curves and how K2 mission works.
Planet transits are small changes in the star’s light, a Jupiter-sized object produces only a 1% drop in the brightness of a Sun-like star and Earth-sized planets generate even smaller dips at the 0.01 % level. Kepler needs the stars to be precisely positioned on its imaging plane in order to achieve the photometric accuracy required to detect these drops in light. To do this the stars have been positioned and kept at the same location with millipixel precision. Kepler was able to achieve this during it’s primary mission and the first half of its extended mission To do this Kepler used three reaction wheels (one for x, y, and z directions) with one backup spare to finely nudge the spacecraft to keep the target stars positioned during a Quarter. Kepler suffered two reaction wheel failures and can no longer operate in this mode. This effectively ended the monitoring of the Kepler field, that Kepler was staring at for 4 years. The drift of the spacecraft was too large that the photometric precision was sufficient enough for a transiting planet search.
This is where K2 comes in. The K2 mission repurposes the Kepler spacecraft. Kepler has thrusters but they are used for coarser pointing corrections, they can’t be used to be the fine adjustments that used to be achieved with the third reaction wheel, but you can use the Sun in a way to be that reaction wheel. This is how K2 works. If Kepler is pointed observing fields that are along the plane of the Solar System, than the two working reaction wheels are used to maintain the x-y locations of the stars on the focal plane with the Sun and thrusters taking care of the rest. Kepler is positioned such that the irradiation of the Sun is balanced which basically keeps the spacecraft from rotating. This is a quasi-stable and every 6 hours or so the spacecraft will start to roll. The thrusters can then be used to roll the spacecraft back to it’s original orientation. (You can see this in the raw light curves just plotted. You can see a Nike check-like feature that dips slowly and rapidly goes up.The light curve processing Andrew does tries to remove as many of those artifacts and others as possible. It does a pretty good job, though occasionally there may be an artifact that remains. ) This scheme works pretty well at keeping the stars on Kepler’s focal view located on the same pixels and achieves photometric precision about 3x time worse than what the original Kepler mission was achieving. With this, we can still find planets around other stars, especially smaller cooler stars.
The K2 light curves we’re currently showing on Planet Hunters come from Campaign 0. Campaign 0 is the first full science grade test field data for the K2 mission. Kepler was staring at a field centered around see a region of the sky plotted in the star chart below. The observations commenced on March 12 and the campaign was completed on March 27th of this year. Campaign 0 serves as a full shake down of the performance of the spacecraft in this new mode of operating. The specific targets Kepler monitored in the Campaign 0 were community driven with astronomer putting proposals for what they wanted to be observed, and were decided by a Time Allocation Committee (TAC) organized by the Kepler team. You can learn more about the observing proposals and selected targets for Campaign 0 here.
On the site we’re only showing roughly 30 days worth of data, that’s because the light curves derived from the second half of Campaign 0 are more indicative of what the rest of the K2 mission will be like, so we’re only looking at that data. The observations at the start of the Campaign 0 were taken with Kepler not in fine pointing mode with a guide star and thus the positional consistency of the target stars over time on the imager is lower, causing a decrease in the photometric accuracy. Therefore we’re focusing on the better quality second half data. Future K2 Campaigns will have the full ~75 days worth of data in fine point mode, and we plan on showing all of the observations on the Planet Hunters website in the future.
We are showing light curves from the Kepler 2-wheel mission for Campaign 0 (a.k.a. “K2 C-0″) now and wanted to explain some issues that you may notice with these data. The K2 C-0 data are poorer quality than what you are used to seeing. The Kepler team is still working optimize the light curves, and this has been made more difficult by instabilities in the pointing control of the spacecraft. You can expect to see more trends and glitches. Furthermore, the first few weeks of K2 C-0 data were not useable so the length of the light curve (in days) is shorter than what you might have expected. All of this should improve for the next campaign, C-1.
A second issue with the K2 C-0 data is that we don’t have access to information about the stars. We know the EPIC numbers, coordinates, brightness of the stars, and the program numbers (telling us who requested observation of the stars). Postdoctoral Fellow Ji Wang has been an enormous help – he wrote a program to filter the published 2MASS and Sloan catalogs and to search for stars within a small radius about the EPIC coordinates. Ji then used the stellar brightness to obtain an unambiguous identification. This helps, but we still don’t know the stellar gravities (radii), masses or spectral types. Therefore, the information we can display for each of the K2 C-0 stars is much more limited than what you are used to seeing.
Since we don’t know the stellar radii, we are not able to make up accurate simulations for the K2 C0 data. To compensate we will show these light curves to more people than usual to build up consensus about the presence of transits.
The K2 data have many more selection effects than the original Kepler data because the targets are drawn from several guest observer programs. However, this is part of the fun – scavenger hunting for planets among the K2 stars is sure to be an adventure!
We are also trying to improve our turn-around time for PH results. Instead of waiting until we obtain telescope time to carry out follow-up data and publish a paper (sometimes a year later!) we will put the high probability transit candidates that you identify on the “Planet Hunters Object of Interest” (or PHOI – which I think is pronounced something like “fooey”). This is supposed to be a fun home-grown analog of the “Kepler Objects of Interest.”
Thanks to Andrew Vanderburg at Harvard University who has extracted these K2 C-0 light curves for Planet Hunters.
The first science data from the new Kepler K2 mission is up on Planet Hunters just waiting to be looked at for new planets, eclipsing binaries, and whatever else lies in the data. This is a set of completely new stars! (Check out the K2 page for more information about the K2 mission.)
This data may go fast, so get classifying now! But don’t worry, there will be more K2 data when the next quarter is released. And when each K2 quarter is finished, keep classifying stars from the four-year Kepler mission to help solve one of the biggest mysteries in astronomy: how common are planets?
The light curves you see on Planet Hunters are not always the light of a single star. Kepler has very very precise but blurry vision. The CCD pixels on Kepler’s focal plane are very big, four arcseconds to be exact. The light measured at each observation from several of these pixels are added together to create the light curve you see on Planet Hunters. So what does this exactly mean? In some cases the Kepler stars are pretty isolated, but in others there are fainter background stars that appear nearby in the sky can get blended with the light from the Kepler target star. It turns out you can hide a lot within 4 arcseconds.
This stellar contamination can impact what we see in the final light curve. If the main Kepler star has a transiting planet, the contaminating star can dilute the transits. The transits will look shallower than they really are, and you’ll estimate a small planet radius. Sometimes the fainter contaminating star is an eclipsing binary. Combined with the light from the brighter Kepler target star, the stellar eclipses from the eclipsing binary are diluted. The secondary eclipse (when the fainter cooler star goes behind the larger brighter star and the smaller cooler star’s light is blocked out) can be diluted such that it’s not seen and the primary stellar eclipse (when the smaller cooler star transits in front of the larger brighter star and blocks out a portion of the brighter star’s light) get shallower, looking like a planet transit. Other times depending on the brightness of the eclipsing binary, it will look like the main Kepler target is the eclipsing binary when it’s not.
This is something the Kepler mission always had to deal with and there are some observational checks and data tests that can help determine whether the transit-like signal is likely coming from the actual Kepler target star. You can take follow-up observations like we did for PH1 b and PH2 b using telescopes with adaptive optics that minimize the blurring effects of the Earth’s atmosphere to zoom in around the Kepler target star to look for contaminating stars. Also you can look for shifts in the position of the brightest pixel during and before and after a transit which signals the transit signal isn’t coming from the primary Kepler target star. Also you can look at the individual pixel by pixel light curves from Kepler (Kepler reads out a subimage around each target star and a small number of those pixels get added together to make the Kepler light curve)and see if the transit signal or eclipsing binary signal is present in every pixel or if you see say an eclipsing binary signal in one pixel making the light curve and in pixels near by around a different star. Here’s an example from some of the Planet Hunters volunteers who examined to see if an eclipsing binary was contaminating a light curve.
Despite Kepler’s slightly blurry eyes, we can use a host of techniques to try and rule out false positives, identify where there is stellar contamination, and still find planets. So bear this in mind when you see the light curves, that although it’s likely most of the star’s light is from the Kepler target star, a tiny portion (in most cases) is contributed by neighboring stars.
As part of the new Planet Hunters classification interface, the Summary page (see below) suggests some hashtags you could use to label the light curves you’re seeing in Talk and in the Talk comment area on the Summary page. A few people on Talk have asked for a full list, so here’s a handy list of the first set of hashtags suggested by the science team at launch of the new Planet Hunters.