For more information on Planet Hunters TESS and how to analyse the data in more detail, head to www.planethunters.coffeeor watch our video series on our YouTube channel!
What are you asking me to do?
Join us in the search for extrasolar planets, planets orbiting stars beyond our Solar System. When a planet passes in front of its parent star, or transits, we see in a drop in light from the star. We ask you to review a lightcurve, (plot of brightness over time) and identify where you see drops in light due a potential transiting a planet. A planet the size of Jupiter, will cause a 1% drop in light when transiting a Sun-like star. A planet the size of the Earth would provide a 0.01% drop in light. Maybe you’ll be the first to know of a new world...
Where does the data come from?
The data that we show on Planet Hunters TESS comes from the Transiting Exoplanet Survey Satellite, or TESS. Over the course of 2 years, the satellite will look at 200,000 of the brightest and closest stars in our solar neighbourhood, finding planets ranging from Earth-sized to gas giants. TESS is the very first all-sky survey that is based in space and provides us with data that would be extremely difficult to collected from the ground. To find out more about TESS have a look at the Research page, or find out more directly from NASA. All of the TESS data, including the resulting catalogs, will be archived by NASA at the Mikulski Archive for Space Telescopes (MAST).
Are you the TESS science team?
We are not part of the TESS science team; we are a separate reach team utilizing the available public TESS data archived by NASA at the Mikulski Archive for Space Telescopes (MAST).
Why can't you say the transits I spotted are a real planet?
Solely based on a TESS lightcurves we can never be 100% sure that there is a planet, even if it exhibits transit-like features. There are many astrophysical phenomena, such as eclipsing binaries, that can result in a false positive, so we initially call all findings 'planet candidates'.
Why can't computers do this?
Computers have been very successful in searching through transit light curves for planet transits. Many planets and planet candidates have been found by automated routines, but not all. There will be many research groups searching the TESS lightcurves for the signatures of planet transits with computer algorithms. But we expect there will be transits in the TESS data that the computer algorithms will miss that human review will easily spot.
What’s the difference between a planet candidate and planet?
We call transit candidates, planet candidates until there are further tests showing it is very likely to be due a planet-sized body. That’s because there are many false positives that can mimic the signature of a planetary transit in a TESS lightcurve. The team has to do several checks and follow-up observations before a planet candidate can become a bonafied planet.
The transit method gives an estimate of the radius only of the body blocking out the target star’s light. For a planet candidate to be verified, we need either a constraint on the mass from another detection technique or a strong statistical reason based on the follow-up observations that indicate those non-planet scenarios (like a blend with a background eclipsing binary) are unlikely.
If I make a mistake, can I go back and edit my classification?
If you mark a transit you can change and edit it until you press the 'done' or 'done & talk' button. However, once you submit your classification it goes straight into our database and you won't be able to change it. But don't worry, each lightcurve is seen by multiple volunteers so our analysis will filter out accidental wrong markings. Just do your best!
How do I know if I'm doing this right?
After you classify a TESS lightcurve we can’t tell you if you’ve spotted a transit or missed it, we’re asking for your help because we don’t know where all the planet transits are the TESS lightcurves. Human beings are really good at pattern recognition, and generally your first answer is likely the right one. Use your best judgement. The examples in the tutorial, field guide, site guide and need some help with this task button can be handy resources. Also ,the simulated light curves that you may encounter are also great examples to learn from.
Do I get credit for my discoveries?
Everyone who contributes to finding a planet through Planet Hunters TESS will be acknowledged and thanked for their contributions on the website and in any papers that we, the Planet Hunters TESS team, write about that planet. Additionally, your Zooniverse username will appear in the MAST database next to all planet candidates that you helped to classify. We will try and announce discoveries rapidly on MAST, though in this first stage it might take us a little while.
Do I have to log in to get credit for my discoveries?
Yes, if you do not log in we don't know who you are and unfortunately we can't credit you for your discoveries. If you create an account and log in we are able to contact you about your discoveries.
What is the PHT publishing policy?
Planet Hunters is the work of a dedicated team, and derives its value from the efforts of the volunteer participants. To ensure credit is given, anyone publishing results based on use of information of talk is required to: 1. Cite Eisner et al. 2. Contact the PH team (Via email to firstname.lastname@example.org) to discuss credit and, where results substantially depend on Planet Hunters, authorship and 3. Give credit to volunteers who have contributed. A list of such volunteers can be provided by the PH team.
Agreement with this policy is necessary in order to use results from the platform.
Do I get to name the exoplanet I found?
At the moment unfortunately not, but maybe in the future. The International Astronomical Union (IAU) is responsible for deciding naming conventions for extrasolar planets. The IAU previously held a public naming campaign for a set of exoplanets. You can find more details here.
The PHT interface used to look different. What has changed? The Zooniverse team has been working extremely hard to improve the Planet Hunters TESS interface and introduce some new features. One of these is the option to zoom in on the lightcurve, giving you the opportunity to explore different parts of the data in more detail. This close up view will give you a better insight into the shape and depth of a potential transit-event and may be able to reveal more about the nature of a dip. The zoom buttons are located on the right hand side of the lightcurve. Remember to click back on the selecting tool to mark a transit once you've finished zooming in.
Are there any keyboard shortcuts?
Once you have click on the lightcurve (or on one of the buttons straight to the right of it) you can use the plus and minus keys on your keyboard to zoom in and out and the right and left arrows to pan across the data.
What causes the gaps in the light curves?
Gaps in the TESS observations happen when the spacecraft is not observing. This is usually because the spacecraft is oriented towards Earth, transmitting its recorded data to Earth. Sometimes it is because the spacecraft is in safemode waiting for commands.
What do the numbers on the vertical axis mean?
The numbers on the vertical axis (y-axis) represents the percentage increase/decrease in brightness with respect to the average brightness of the star. The brightness increases from fainter at the bottom to brighter at the top of the figure.
What do the times on the horizonal axis mean?
The time on the horizonal axis (x-axis) is the time with respect to the time of the first useable observation.
Why are there simulated transits?
In order for the science team to understand what kind of planets we can and can't find with Planet Hunters TESS we show you lightcurves where we know all the properties of the planetary system. This helps us gain a more complete understanding of the range of planets that are in our Galaxy and is vital to our statistical analysis of the results. The simulated data is there to test the system, not you, and we will always tell you if you have just classified a simulated transit. Find out more on the Research page.
How is this different from the previous Planet Hunters projects?
The previous Planet Hunters projects used data from the NASA Kepler spacecraft, whereas the new Planet Hunters uses TESS data. TESS is an all-sky survey and will look at 400 times as many stars as Kepler did. Furthermore, TESS will monitor closer and brighter stars making it easier for us to follow up planet candidates with ground-based telescopes. The layout of both projects are very similar, but there is a new core Science team. We thank everyone who has participated in previous versions of Planet Hunters as either a volunteer or as a scientist!
I have a question or I found something interesting, who should I talk to?
Head over to Talk and start a discussion there. The Planet Hunters TESS community including members of the science team will likely join in. You can also click the 'Done & Talk' button when classifying and post a comment and/or a hashtag to mark and describe the lightcurve you classified on its Talk page.
I have found an interesting signal, how can I find out more about it?
These videos take you through how to interpret a transit like signal (we recommend watching the video series from the beginning but you can also jump right in with these!)
or these (all of the accompanying coding notebooks can be downloaded from here - where you can also find introductory videos to coding!).
How can we determine the size of a planet we're looking at? Why are transit shapes different? 7 steps to identify a good exoplanet candidate
I'm a researcher interested in using the Planet Hunters TESS planet candidates, what do I do?
We will shortly be providing up to date assessments from Planet Hunters TESS to MAST. Head over to the TESS MAST Homepage for more information, or contact the science team through this site.
How do I keep up to date on the latest Planet Hunters TESS news?
Check out our blog and Talk for the latest planet hunting news. We’ll also post frequent updates on our Twitter and Facebook accounts.
Data Reduction Guide
Think you've found a great transit candidate? Can't wait for us researchers to look into it? Here are a few things that you can do yourself to check whether your candidate could be a real planet. These are the first steps that we would do ourselves, so it's a great help to us if you have the time or inclination to make a start yourself - and a great opportunity to learn a few cool things in the process. Note you can do as many or as few of the steps on this list as you like - it's completely up to you!
More information on this can be found on www.planethunters.coffeeor in our video series at YouTube channel!
1. Is it a TOI (Tess Object of Interest)? Watch this video to find out more!
TOI is the name used by the TESS team for good planet candidates that they have checked carefully and consider worthy of follow-up observations.
In order to check whether the candidate is a TOI you need to find the TIC number (you can view it by clicking the "i" icon below the subject image in Talk) and check if it appears on the TESS data alerts page: https://archive.stsci.edu/prepds/tess-data-alerts. TIC ID is the first column in the big table. If the candidate is on the TOI list, well done – you have found a candidate that the TESS team have identified as a planet candidate.
If the candidate you found is a TOI, that means you're doing really well. However, it's already being looked into by the TESS team, so we won't duplicate their efforts - we want to focus on anything that they haven't already found. Before you leave the talk page for that subject though, please tell everyone else what you've found - you can say "This is Tess Object of Interest (TOI) XXX" where XXX is the number that appears in the 2nd column on the data alerts table.
2. Is it a TCE (Threshold Crossing Event)? Watch this video to find out more!
All of the TESS data are passed through the TESS transit search pipeline, which automatically flags any lightcurves that might contain a planet. TCEs are the raw flagged candidates of this pipeline (prior to any vetting done by the TESS team).
In order to check whether a candidate is a TCE you can download a CSV file, for each sector, where they are all listed: https://archive.stsci.edu/tess/bulk_downloads/bulk_downloads_tce.html.
Alternatively you can check if a given candidate is a TCE using EXOMAST (https://exo.mast.stsci.edu/). On EXOMAST, simply enter "TIC " followed by the TIC number, and click ‘search’. If the candidate you are looking into is a TCE, you will be taken to a page containing some information about the host star and the potential planetary system.
If the candidate is not a TCE, you will see a notification below the search bar stating “No planet found”.
If you find a TCE, once again, you're doing really well - it means that you're as good at finding (some) transits as the pipeline that professional astronomers developed over a number of years! Please flag such an object as a #TCE on the talk page (if possible including a link to the EXOMAST page for that TCE).
3. It’s a TCE but not TOI?
A candidate that is a TCE but not a TOI is an object that the TESS pipeline flagged, but the TESS team decided wasn't a good enough planet candidate to be promoted to TOI status. Finding these is really great, not least because - in some cases - we might take a different view and consider them to be likely planet candidates. So if you have found a TCE that isn't a TOI, please let us know by including "@researchers" in your comment on talk. We will get notified automatically and - time permitting - we will look at it more closely.
When vetting the TCEs, the TESS team perform a long list of checks. These tests are designed to weed out instrumental false positive (the signal isn't real) and astrophysical false positives (the signal is real but isn't caused by a planet, but something else). The results of these tests are saved in a DV (data validation) report, which they have helpfully made publicly available - so we can use them to understand why the TCE didn't become a TOI. This is a really quick way to look through candidates and to avoid repeating the hard work that the TESS team have already done. The DV reports are long and complex, and also currently a little tricky to access for TCEs that aren't TOIs, so we are not including instructions on downloading and using DV reports in this post (though we hope to do so at a later date). Here is a video on how to interpret DV reports: How do I download data vetting (DV) reports from exo.MAST and what do they mean?
Importantly, there are already a few TCE (and not TOI) candidates found by planethunters.org volunteers for which we have examined the DV reports and come to the conclusion that the candidates are actually promising. This mainly happens because the TESS pipeline requires at least two transits for a detection, so it only searches for transits that repeat with periods up to the duration of a TESS sector (~28 days). If there is only one real transit, it might be missed altogether (this is where you volunteers come in!) or it might be wrongly paired up with an artefact or noise feature somewhere else in the light curve. In that case, the diagnostics in the DV report, which are based on all the transits combined, might be misleading.
4. Create a cutout or movie of the TESS data
You can look into the signal more and help us determine whether the signal is real or not. If a signal is not caused by a planet, we call this a false positive. Now there are two main types of false positives: instrumental (for example due to the TESS satellite being slightly unstable at certain times, and astrophysics (for example an eclipsing binary or an asteroid passing close to the target).
We discuss various false positive scenarios and how you can look into these yourself in our video series. Here are the main videos that discuss this (but we recommend you watch the video series from the start as they build on each other).
How do we rule out false positives using the background flux? How do we rule out false positives using target pixel files? How do we rule out false positives using centroid motion? How can the nearest neighbor stars tell you about systematics and asteroids? How can I use LATTE to rule out false positives? How do odd/even transits help rule out false positives?
5. Create a cutout or movie of the TESS data
There is a fun tool at https://mast.stsci.edu/tesscut/ which allows you to extract a time-series of cutout images around a given target. You can use these to look at what is in the vicinity of the target, or even to make a movie! If the transit is deep enough, you might even see the star "blink" (this can be a fun thing to try out on variable stars or eclipsing binaries too).
Sometimes, what appears to look like a transit is actually due to some weird artefacts, affectionately dubbed "fireflies" or "fireworks" by the TESS team, that sweep through the field of view. These are probably due to scattered light from bright stars or moving objects inside the telescope and camera optics. If you notice that a promising candidate is actually due to such an artefact, please let everyone know on talk!
6. Here's a video that summarised the 7 steps to analyse a signal once you have identified it!
Didn't find an answer to your question? Visit Talk and ask the Planet Hunters TESS Talk Community.