Exoplanet Atmospheres and SETI
Narrowing the Search: SETILive is a part of the much larger, much broader and rapidly advancing field of exoplanetary research. The “S” in SETI stands for “search” and these advances will directly benefit SETI by narrowing the search. The current explosion in exoplanet discoveries ignited by the Kepler project is providing great fundamental data for planetary and astrobiology scientists to begin figuring out exactly how planets form and develop and what the prospects for life on these planets could be. The more they learn, the narrower the search for ET can be.
The SETI Institute’s concentration on these Kepler planets, with SETILive as a part of it, is an early example of this more informed search, focusing for the first time on a large number of planets that have good evidence that they could be in the water-based habitable zone. The new wave of discoveries that will help narrow down this search even more is the analysis of exoplanet atmospheres – finding out what gases are present. Some of these gases, if found, could be a strong indication that a planet hosts life at some level, and quite possibly intelligent life.
New Techniques: A sign of the progress being made in the study of exoplanet atmospheres is this work done through the European Southern Observatory also reported on spacedaily.com. Here, they are directly measuring the very weak “rainbow” of colors from the planet’s faint infrared glow produced by its own heat. This new technique is different than the method of seeing how the planet’s atmosphere affects the rainbow spectrum of the starlight behind it during a transit. It is based on that fact that, like a star, a planet’s own rainbow spectrum is affected by gases that surround it. The difference is that the planet’s rainbow light is very much weaker than a star’s and it’s concentrated in infrared wavelengths that are far out of the range visible to our eyes.
On the Horizon: So far, exoplanet atmospheric measurements are only feasible for large planets like this Jupiter-class one in a nearby star system. Measurements for smaller (earth-class), and more distant planets will come along in the coming decades as new instruments like the James Webb Space Telescope and the new giant ground-based telescopes come into play.
I feel that we’re at the beginning of a very exciting few decades in the search for extraterrestrial life in general and SETI in particular.
SETIcon II This Weekend, Lots of Prime Telescope Time
SETIcon II Event: This weekend the SETI Institute presents SETIcon II, in Santa Clara, California, US. It’s billed as ” a unique, entertaining and enlightening public event where science and imagination meet” on the event website. It looks to me like it will fill that bill and I wish I could have attended. If I lived anywhere near the Bay Area… road-trip, most definitely. It will feature SETILive in one of the many interesting exhibits. Other than it being of general interest to “SETIzen scientists” here at SETILive, it also means our “Telescope Active” time is going a bit off the normal routine for about a week, but there’s a good reason…
Lots of Prime Weekend Telescope Time: We normally observe the Kepler star field, looking for signals from specific stars determined by the Kepler project to have planets likely in the liquid water-based habitable zone. That star field is currently only above the horizon and visible from the ATA from late evening to mid-morning US time, and the other time is filled by other observing projects looking at different parts of the sky. By lending some SETILive active time from late evening and morning sessions during weekdays this week and next to other ATA projects, the SETI Institute can give it back to SETILive this weekend for a pretty full daytime schedule in the Americas and from late afternoon to early morning east of the Atlantic. They’re filling the US daytime schedule this weekend by feeding us data from other exoplanet candidates outside the Kepler field when it’s below the horizon. So, SETIcon II attendees will be able to see it work and work with it themselves using live data and of course, you can get on and classify live data this weekend at times you aren’t normally be able to.
You can see the upcoming schedule along with the current status, as always, at setiquest.info.
BTW: Telescope Active Window Slowly Shifts: By the way, and speaking of active telescope windows, six months from now the Kepler viewing window, and therefore our “Telescope Active” times, will have shifted by 12 hours and will be pretty much all during daytime hours in US . The apparent motions of Kepler field stars in the sky, like all extra-solar objects are due to the true rotation period of the Earth, the sidereal day which is about 4 minutes shorter than our solar day. In six months, this small shift accumulates to half of a day, or 12 hours.
Simulations! (late, but how would Scotty have handled it?)
It’s been about five weeks since my last post where I announced we’d start testing follow-ups in the background and also that some improvements to the waterfalls along with adding simulated ET signals to them were imminent. Well, we checked those subtle but important waterfall improvements off the t0-do list two weeks later and yesterday, at about 21:30 UTC, we finally got simulations live. It took five weeks – longer than we had figured, but like most science and engineering tasks, you’re doing something new and don’t always know what you’re getting into until you start making it work. Now, Star Trek’s Chief Engineer Lt. Commander Scott (“Scotty”) might have figured that it should take a week, multiply that by five to get the real time for the task and then multiply it again by five and tell the captain it would take 25 weeks. The Captain would demand it in five and Scotty would say “I’ll do my best, Captain”, self-satisfied and with a barely visible smile. I’ll try to be more Scotty-like in the future.
Trekkies: I know that the Star Trek franchise has alluded to and made references to this process over the years. Any specifics about those references would be appreciated.
Our primary purpose for inserting simulations (“sims”) into the waterfalls is to conduct a controlled experiment which will measure the statistics on how well you, as a group, are able to detect a signal in a waterfall with noise and sometimes RFI signals in the background. The results we get will be an important part of a peer-reviewed scientific paper we plan to eventually publish and we’ll make comparisons to some basic computer algorithms. So, you’ll be a part of these real, important scientific results derived from the SETILive project.
Another benefit of adding sims that users have pointed out is that it’s an occasional “test” that helps us be sure we continue to be careful, looking closely for that weak signal track that’s fading in and out and seems to sort of follow a line. It could be a signal of interest, trigger a follow-up and who knows, even make it to “Wow!” status.
The sims have random positions, angles, “wandering” patterns and randomly fade in an out in brightness to emulate typical signals. The two key parameters that are systematically varied over wide ranges are brightness and how much they randomly move from side to side (“erratic-ness”) . Because we’re trying to find the limits of our users’ ability to pick these out, some will be so dim that no one would be able to see them, so don’t feel badly when we show you where a simulation was that you missed. Currently, you can’t see just how dim a missed simulation was and we’ll look into whether or not we should change that. We have to carefully consider doing anything that might affect how you as a group do the classifying. It might add an unwanted variable into the statistics. There have been some good suggestions on Talk for how to do it if we can – thanks!
Speaking of follow-ups, that’s been an even tougher slog. We’re doing something that hasn’t really been tried before. Yes, SETILive follow-ups are modeled after the automatic ones that are already working at the ATA, but replacing detection algorithms and calls to local computer programs at the ATA with the remote,web-based, human-in-the-loop SETILive detection process is quite different in many details so requires some programming and communication protocols that are not already there. We also can only work at certain times in the ATA schedule and also have to deal with scheduling around the availability of the experts who are making it work. It’s coming along, and we feel it will be working soon. When will it be live? I’m afraid we can’t really say exactly. Where’s Scotty when you need him? He’d have an answer.
What’s the word? Follow-ups! (and more)
We haven’t posted an update since March 25th and one volunteer pointed that out to me in a message and then asked: “What’s the word?” Well, it’s “follow-ups”… mostly. We’re finally going to start testing live follow-ups next week. We’ll be doing the testing in the background at first and until we’re certain that it’s working properly, you won’t be able to tell that we’re doing it and the “Followups” counter on your profile will remain zero. Once we’re sure it’s working, we’ll start updating the follow-up counters and let you know anytime a follow-up gets to a certain level. Early next week, we’ll also go live with some subtle, but very important changes: We’ll improve the waterfall display processing and we’ll be adding simulated ET signals. Read on…
Follow-ups
Being able to do follow-ups is a unique and exciting SETILive capability. If enough users mark a signal that appears in only one waterfall diagram (and therefore a potential ET candidate), the ATA telescope can be commanded to immediately go back to collect and send us more data from that target so we see if it still looks like ET through our usual marking. If it still shows up in the same single beam, a second followup will be triggered and then basically “rinse and repeat” as long as it continues to look potentially ET. Anyone classifying signals when this happens will be getting the follow-up waterfalls for classifying as well.
When they are enabled, tested, and fully active with live notifications (hopefully next week), we expect first follow-ups to happen pretty often as you might expect since single-beam signals are not that unusual. Terrestrial signals can often appear in one beam since the amount of signal that leaks into each beam varies quite a bit and if the signal is weak, it might not be strong enough for us to see it leaking into two of the beams. The leakage can change quite a bit as the ATA adjusts its beams to track the celestial sources and as the terrestrial source (an airplane, satellite, etc. ) moves with respect to the ATA. So, if a terrestrial source happened to look ET in one set of waterfalls, it likely won’t look that way in the next set we get several minutes later when the geometry has changed between the ATA and the RFI source. So, most followups won’t go past the second level and we won’t be notifying you that a follow-up is in progress unless it survives the second set of markings. At that point you’ll know that we’re starting to track a potential ET and that will be quite exciting even though it’s very unlikely to continue to pass the following ET tests. If it does… well, now that could get very exciting.
We’ll be randomly adding simulated ET signals so that we can measure our detection capabilities. As soon as you finish with a classification having an artificial signal, we’ll let you know where the signal was on the waterfall. In order to make this measurement more consistent and useful and to improve your ability to see weak signals in general, we’ll also change the waterfall processing and display to give them a more consistent brightness scale. It should improve your ability to make out very weak signals even when there’s some stronger RFI there too.
The main thing you might notice with the new waterfall processing is that the background noise pattern of random bright and dim spots will be more consistent and a bit more “filled in”. We hope this will help you pick out weak signals better and more often. It might even help reduce our tendency to see signal patterns in the noise – I’m not sure about that, though. Part of this improvement comes from keeping bright signals from causing the background to get dimmer. A side benefit is that the dark banding caused by strong signals going bright then dim should be less severe. I already know that you’ll probably see some new artifacts in the noise background that the old processing took out and we encourage you to point these and other things out in Talk as you did with the old processing, especially if it makes classification difficult. When it goes live, I’ll create a new Featured Topic on Talk for you to post any comments about these display changes and the artificial ET signals.
The statistics we collect on your classification of these artificial signals in the presence of terrestrial RFI signals will eventually become part of a peer-reviewed and published scientific paper. So, it’s important for you to continue to make your best effort at marking all signals in each waterfall as well as those that might be ET. We need to know what else was in the waterfall to properly measure our collective detection capability in the presence of a variety of RFI signals.
Thanks for your continued participation and I hope you look forward to the SETILive going to the next level with live follow-ups as much as we do.
Lou Nigra
SETILive Science Team
Science in the Moment
I’m Lou Nigra and have the good fortune to be Project Scientist for SETI Live and I’d like tell you about what we’re doing and why.
The SETI Live project’s goal is to take the Search for Extraterrestrial Intelligence (SETI) into the large chunks of radio frequency spectrum previously made mostly useless by the human-made Radio Frequency Interference (RFI) that crowds them from sources like GPS satellites and mobile phone networks. We’ll do this by showing you radio frequency signals direct from the SETI Institute’s Allen Telescope Array (ATA) as they are received while looking in the direction of stars that according to the Kepler telescope (and sometimes our sister project, Planet Hunters) have planets where liquid water is likely and so have the best chance of hosting an ET civilization producing radio signals of their own. Not only that, we’ll be putting you “in the loop” – if enough of you see a potential ET signal in the same data, then within minutes, the ATA will be interrupted and sent back to take a second look. This is already pretty exciting on several levels – you’ll process SETI data fresh off the telescope, the telescope will be pointed at stars with promising planets, and if you identify something ET-like, it could trigger a follow-up measurement. Now, this is basically what the ATA computers normally do, so why bring a bunch of citizen scientists into the loop?
Cleverly conceived computer algorithms used by the SETI Institute are extremely good at identifying potential ET signals in the presence of simple forms of RFI or small amounts of it. They become confused and unreliable when too much RFI begins to make the data too complex and chaotic. This is where you come in. Maybe it’s because humans evolved in a basically chaotic world that our sight (and other senses) are so good at picking out of that chaos the patterns that are important to us at the moment. Because of this, we believe that the human eye… well actually the human brain, will be much better suited than a computer algorithm to finding the weak, but orderly engineered signals we expect to intercept from a distant ET civilization amidst the complex and sometimes chaotic background of RFI.
Aside from the very important contribution to SETI science of opening up new frequency spectrum to the search, there are other scientific results we expect to get from SETILive. For one thing, we don’t know just how weak an ET signal you’ll be able to identify. So, we’re going to evaluate this by occasionally inserting data with an artificial ET test signal and collecting statistics on the results. Don’t worry, we will tell you immediately after you’ve classified one of these that it had a test ET signal and whether you caught it or not. We also don’t yet know the best ways to visually present this data to users that will make it easiest to pick out ET-like signals. We expect this to evolve as the project progresses and we’ll evaluate how successful you are with different visualizations. We expect to publish the results of both of these studies so you will be contributing to some important signal analysis science. Some of this may also lead to improving SETI computer algorithms.
We’ll start with a simple display that is widely used and very effective throughout radio astronomy: The “waterfall” display. Here the data is shown to you in a set of images, each of which shows all the frequencies in a particular bit of spectrum coming from a particular Kepler target’s direction, the strength of each frequency, and also how this changes with time. We’ll also give you some graphical tools to identify signals with frequency patterns that could be of interest.
Welcome to this unique Zooniverse project! I’m very excited to be a part of it and I look forward to working with you all.
What We Do With Your Classifications
What Data Do You See?
On SETI Live you are looking at ‘live’ data from the telescope. Every second, SonATA (SETI on the Allen Telescope Array) reports the power measured in individual frequency channels that are 1 Hz wide. While the SonATA system is dealing with more than 20 million such channels, for each beam on the sky, SETI Live is concentrating on only a few bands of channels that are crowded with signals.
Each waterfall plot displays the power in each of 533 channels horizontally, with each vertical row being a new time sample. The most recently sampled data is at the top of the plot. The brightness of the pixels represents how strong the signals are.
There are two or three separate waterfall plots for each observation, because the SonATA system looks at different target planetary systems at the same time. If a signal is really coming from one of the targets, it should be in only one of the plots – this is the sort of signal that might be from ETI. If the same signal can be seen in multiple plots, then it is some sort of interference of RFI that is entering into what we call the telescope sidelobes. Your eyes have peripheral vision, and so does a telescope – that’s what we call sidelobes. It is hard to distinguish a loud signal in the sidelobes from a weak signal in the telescope beam. Looking at multiple targets at the same time helps us figure this out.
How Does the Crowd Find ET?
During the initial observations, signals that you identify as being in only one beam, having some non-zero drift rate, and never having been seen before, become interesting candidates to be real ET signals. So when the current cycle of data acquisition ends, SonATA will retune the telescope’s frequencies and look back at the same target and frequency to try to reacquire that signal again. But SonATA is still blind to the crowded bands and so you will have to help with this follow up.
If the candidate signal you found was changing frequency over time, SonATA will predict the frequency where it should now be found, and generate waterfall plots for you to observe. Is the same signal still there? Is it in any other beam? If the answer to the first question is yes, and to the second question is no, this candidate remains of interest. Otherwise it will be classified as being due to chance noise, or interference.
A candidate that’s still interesting automatically generates an observation ‘off-source’ in the next data acquisition cycle. These new data will be presented to you. Is it still possible to see the signal? If so, it is coming from somewhere other than the target we were looking at and is therefore interference. If it isn’t seen ‘off-source’ than the next observing cycle will look back at the target.
This automated on/off cycle will continue 5 times, or until the signal is identified ‘off-source’ or fails to be seen again while pointing on the target. After 5 cycles, SETI scientists are alerted and humans take over the logic of where to point the telescope next – this is a rare, but very exciting occurrence! You are still critical because you’ve been classifying this signal up to now and are the experts on recognizing it. We’ll all look together to figure out how to proceed and what other questions to ask.
SETILive 