3 million classifications and counting….
This weekend we hit the 3 million mark for the number of classifications made by the PH community, thanks to all of you. On behalf of the entire team, I want to say a big thank you to everyone for all of your hard work and your time. We can’t believe in the span of 6 months we’ve gone from 0 to 3 million classifications.
So what does this mean for the project? Well we’ve completed the Quarter 1 data released in June 2010, finished about 20% of the Quarter 2 data, and we have uploaded ~5800 new light curves from Q1 that were released in Feb onto the site. So not to worry, we still have plenty of Kepler data to sift through. The science team is working hard at following up our planet candidates with the Keck telescopes and developing better algorithms to search the classification database and go from transit boxes to extracting transits and planet candidates (just this past week I spent some time at the Adler Planetarium with Chris working on this. More on that to come soon).
I thought it might be interesting to take a look at some of the user statistics for Planet Hunters (all these numbers are as of a few days ago). We’ve had over 40,000 people make classifications, with 27,142 from logged in Zooniverse users. The bulk of our classifications come from zooites with Zooniverse IDs. On average a typical logged-in PH user has examined 104 stars and non-logged in users look at about 3 stars. About 86% of our logged in zooites, classify 100 light curves or less. 71 uses have classified over 5,000 light curves, and 19 have hit the 10,000 mark (Congratulations to all of you, and you know who you are 🙂 ). Two users have classified over 50,000 light curves with a single user having looked at over 88,000 light curves since the project launched. Thanks again to everyone for all your classifications.
Happy Hunting and onward towards 6 million classifications,
~Meg
365 Days of Astronomy Podcast
The podcast featured today over at 365 Days of Astronomy is about Planet Hunters. A couple of weeks ago, Chris and I sat down and chatted about Planet Hunter from launch to today, some of the latest results from the project, and what the science team’s been working on . Take a listen, and we hope you enjoy it.
Should you mark it as a transit?
A question that comes up regularly on Talk is whether you should mark something as a potential transit. A lot of people are apprehensive about giving a “wrong” answer. Rest assured, there’s no such thing as a wrong answer. You are classifying real data where the true answer simply isn’t known – that’s at the heart of science.
So what should you do if you’re not sure? If your instinct tells you that a feature might be a real transit, you should mark it. The reason for this is that that’s where the real information comes from. Other people will see the same data and classify it independently of you. Citizen science projects like Planethunters tap into the “Wisdom of the Crowd” effect where the decision (classifications) of a large group can be more effective than a single expert.
But for this to work, we need a diverse and independent set of classifications. So next time you worry about whether to click on something, listen to your own experience and instinct, and if in doubt, click on it. If it’s a real transit, chances are others will click on it too.
Inverse Transits
I was talking to last week’s seminar speaker, and we were talking about Planet Hunters and some of the things that might be lurking in the Kepler data. One cool thought is there might be inverse transits so instead of dimming events, instead the star actually appears brighter.
There are lots of eclipsing binaries that you’ve probably seen as you’ve been classified, but another interesting type of eclipsing binary might be a transiting white dwarf orbiting a main sequence star. White dwarfs are about the same size or a little bit bigger than the Earth about half as massive as the Sun. Depending on where the white dwarf orbits, there could be magnification causing a brightening as the white dwarf crosses in front it’s companion star. This magnification is caused by gravitational microlensing, where a massive object bends light of a background source resulting in images of the source that are magnified and distorted. Transiting exoplanets are not massive enough to bend and distort the light of their companion stars significantly. For eclipsing binaries it looks white dwarfs are in the sweet spot, if they are orbiting extremely close to their partner main sequence star. Papers in 2003 by Sahu and Gilliland (2003) and Farmer and Agol predicted that Kepler might be able to detect such events. In these cases during the transiting event, the ligthcurve gets brighter rather than fainter. These events last as long as the transit does so only a few hours (if the white dwarf is orbiting at 1 AU the event is ~10 hours in duration).
Here’s some examples from a paper by Sahu and Gilliland (2003) .
A transiting 0.6 solar mass white dwarf orbiting at 1 AU
0.6 solar mass white dwarf at different orbital radii from a solar-type star
There are some estimates of how many might be there ranging from a few to a about a hundred or so events in the Kepler monitored stars, but we really don’t know. No one has detected them, and there could be 1 or none but with so many eyeballs staring at the data, we might uncover them if they’re there. Anyone seen anything like this in the light curves you’ve classified? It would be very exciting if we found one, it would be the first such discovery – if you see an inverse transit like the examples above, please share on Talk and let us know about your discovery!
Cheers,
~Meg
Transit Fitting
By Charlie Sharzer. Charlie is an undergraduate at Yale working on model fitting the PH planet candidates to estimate their radii and periods
Hey everyone! For the last month and a half I have been playing around with a program called LCME (Light Curves Made Easy) written by our own Matt Giguere modeling the Planet Hunters planet candidates. The program creates a graphical user interface that can be used to evaluate the same light curves you see when looking for transits. All I have to do is enter the ID# of a promising star, and it displays the curve in a graph. I click around for a few minutes, marking where I think the transits are on the graph, and the program is able to estimate the location and duration of all potential transits. It then uses this information to get what we really want: an estimate for the radius and period of the planet candidate.
On the technical side of things, once I point out the parts of the graph with dips in the light curve, I can ask the program to trace a curve mirroring the data using a box-least-squares fit. The box version of the least-squares method, not unlike finding a standard deviation, attempts to minimize the error between the components of each point’s position vector and a linear (or nonlinear) trendline that fits the data. Most significantly, it can “predict” the further locations of dips in the light curve that I don’t personally highlight.
If the data is confusing or the least squares fit gives a worse estimate than my own (as was the case last week when I was examining a multiple planet system) I can phase-fold the data to get a more accurate reading. This stacks the mini-image of each period of transit on top of each other and finds the mean values to create a totally new array that is (hopefully!) more accurate. I can also use the Levenberg-Marquadt algorithm to minimize the sum of the squares of the deviations of all points from the least-squares-fitted curve, or make a lomb-scargle periodogram to, if the light is broken down into frequencies, find the time at which sample frequencies are mutually orthogonal.
via seo company
Keck Follow-up
Hello PlanetHunters! The Kepler field is finally visible and tonight, grad student John Brewer and I began observing a few of the candidates that you identified. We are operating the Keck telescope in Hawaii remotely from New Haven, CT. The weather in New Haven may not be great tonight, but it’s perfect in Hawaii – we have clear skies!
There were several steps involved in selecting the best candidates to observe tonight.
- You all did the hard first step, classifying data from Q1 to identify prospective transits.
- Stuart extracted 3500 prospective transits from the database.
- We examined all of your selections by eye – about 100 planet candidates survived (many transits per candidates).
- Yale grad student, Matt Giguere, wrote computer programs to model the light curves and to search for evidence of blended background binary stars. Visiting grad student, Thibault Sartori, has been using this code for the past several weeks to model all of the planet candidates – about half of the 100 planet candidates survived that analysis.
- John and I will analyze the spectra we collect tonight to derive stellar parameters (temperature, surface gravity and chemical composition) – this will help to better constrain the planet radius.
- Jason Rowe and Natalie Batalha from the Kepler team kindly agreed to analyze our top candidates with the Kepler data verification pipeline to help eliminate additional false positives.
It will be tough to go to the next level and confirm any of these as planets because the stars are faint. It is sure easy to understand why the Kepler team has more than 1200 planet candidates, but currently only 11 confirmed planet-hosting stars. It is a long road from planet candidate to a bonafide planet!
Introducing the Planetometer™
Introducing the new and fantastic Planetometer™ created by Planet Hunters lead developer Stuart Lynn. Here you can watch the number of classifications in real time. Additionally we’re streaming the planet candidates and the usernames of those who identified them. If you have a mac you can also make the Planetometer™ as your screensaver. Download the dmg here. As part of Chicago’s Adler Planetarium’s Spring Break at the Adler Seo Company (March 24-April 24) Planet Hunters is being featured and the Planetometer™ is being streamed live there for everyone to see.
Cheers,
~Meg and Stuart
Telescope Proposal
Hey everyone,
Yesterday myself, Meg, Chris and the rest of the Planet Hunters team where working hard to get us to the next stage of discovery with Planet Hunters. As you all know we have been really successful at finding interesting objects that the Kepler team’s automated algorithm has missed. Our first trawl through the data has netted us lots of potential planet discoveries. While this is great we really want to remove the potential from the sentence! So yesterday the team submitted a proposal to to the Keck telescope to request time to follow up the results from the site.
The Keck telescope is a wonderful instrument located 4,145 metres up, near the summit of Mauna Kea in Hawai’i. Composed of two telescopes each with a mirror 10 metres across, it is one of the best astronomical instruments in existence.
Unfortunately this means Keck, like most modern telescopes, is large, complex and therefore expensive. It cant be run by any one team or even any one country. It might be many times larger than your telescope at home but at least you get to look through that telescope whenever you want, while astronomers have to share time on Keck. Infact share is even stretching it a little, what actually happens is astronomers compete each year for time on the telescope. Unfortunately this competition doesn’t involve some kind of X-Factor public voting system (otherwise we could get all you guys to rig it for us) but rather is decided by a board of scientists who run the Keck telescope. Each year they receive a lot of requests from scientists to use their magnificent instrument but there is only enough time for a limited number of observations. The science team for Keck will independently asses each request for scientific merit, practicality and interest to decide who gets those valuable hours gathering photons.
To make matters worse pretty much every telescope, on earth or in space, has this competition at the same time each year. This means that astronomers all over the world scramble to get their proposals in and astronomy departments are full of sleep-deprived, very stressed-out people. Meg, who did the lion’s share of the work for our proposal, also had another 2 due at the same time for different telescopes! She somehow managed to get them all in and I hope is even now sleeping to recover from her ordeal. Thanks, Meg!
We have asked them for two nights worth of observing time using the HIRES instrument on Keck. During this time we point the telescope at and take spectra of our top planet candidate hosts. This will let us do two things, learn more about the host stars themselves to lets us characterise the potential planets better, but more excitingly it will let us look for the telltale wobble of the host star. If we see this it would would give us independent confirmation what we are seeing is really an exo-planet! At that point we can bin that annoying “potential” prefix and say without fear of contradiction that you, the Zooites of Planet Hunters, have discovered a new world !
We are by no means guaranteed to get the time but we all have our fingers crossed and we will let you know as soon as we do.
Science and Progress: Short Period Planets in Q1
Chris Lintott (Zookeeper Chris) and I wanted to give an update on what the team is working on and some of the changes made to the PH site to help us answer the question we are tackling right now. We used very simple cuts and visual inspection to come up with a preliminary list of planet candidates that John has discussed in an earlier post. We’ve been brainstorming on how to combine the results from all the multiple user classifications (about 10 users looking at each lightcurve) to tease out every transit in the database of over 2.0 million classifications. We are working hard on more sophisticated algorithms and techniques to take all your Q1 classifications and transit boxes and extract transits and planet candidates.
After starting to look at your classifications and results from the simulated transits, Chris and I think an interesting question to look at is what are the abundances of planets on short period orbits (less than 15 days ) in the Q1 data. The Kepler team is doing something similar and it will be very interesting to compare the two results. As an initial step we are only looking at planets bigger than 2 Earth radii so only gas and ice giants because the transits are more pronounced than the smaller rocky planets. Less than 2 Earth radii will be much harder to detect, so we first we want to develop the analysis tools and then we’ll come back to the less than 2 Earth radii planets later.
With just the transit discoveries alone we can’t answer this question. This is because we don’t know how complete the sample is. If we found 120 Neptune-sized planets for example, we can’t say anything about their abundance compared to Jupiter-sized planets, since we don’t know how many we might have missed in the data set. This is where the synthetic transits we insert into the interface play an important role. If users flag 100% of the Jupiter-sized simulations with orbital periods shorter than 15 days, but only 50% of the Neptune-sized synthetic transits, then we know that the number of transiting Neptunes in the real light curves is a factor of two larger than what we found. With this completeness estimate we can debias our sample and begin to understand the spectrum of solar systems providing crucial context for own solar system.
We find that we need higher numbers and finer resolution in period and radii for the synthetic lightcurves to do this analysis. Starting today, mixed in with the Q2 data, we will be showing newly generated synthetic Q1 lightcurves specifically made for this task. As always with the simulated transits ,we will identify the simulated transit points in red after you’ve classified the star and will mark the lightcurve as simulated data in Talk . With the results from these synthetics we can better tweak our analysis tools for extracting transits from your classifications as well as get sufficient numbers to calculate the short period planet detection efficiency for Planet Hunters. The new synthetics won’t be the only non-Q2 lightcurves you see. We also have about 5800 additional lightcurves from Q1 that were released by the Kepler team on Feb 1st,. Now that the Q2 data upload is complete, these have now been introduced into the database and we’ll be showing these mixed in the classify interface as well as a small subset of the Q1 data previously looked at to examine how classifications have changed over time since December.
Chris and I have are aiming to have the bulk of the analysis complete before October, so we can present the results at the joint meeting of the European Planetary Science Congress (EPSC) and the American Astronomical Society Division for Planetary Sciences (DPS) meeting being held in Nantes, France, in October. We will keep you posted on our progress and results as time goes on. Abstracts are due in May, and so we need to start work now to be able to have results for the Nantes meeting. With your help, we think this will lead to a very interesting paper.
Cheers,
Q2 Data now fully online!
Hi all –
The Q2 data (chopped up into Q2.1, Q2.2 and Q2.3) are now fully online. Since these data cover a much longer time frame than just the Q1 data, we can now start looking for planets with longer periods. If you spot a single transit in a light curve that you think looks good, why not check all the other data (bot Q1 and Q2) for similar transits; it may be a long period planet.
Why is this so interesting? A planet around a star like our sun that is far enough away not to be fried by the star takes about one year to go around the star once. So you’d see one transit every year. Like our own earth. Around a dimmer star than our sun, the habitable zone is closer in, but still long. So happy hunting, especially for long period transits!
Planet Hunters 