“It’s like Rubin Observatory is Netflix streaming the movie out to the public, in this case our scientific community,” said Dr. Bob Blum.
| Guest: | Dr. Bob Blum |
| Title: | Director, Rubin Observatory operations |
| Summary: | The launch of Rubin Observatory’s alert system marks a breakthrough in astrophysics, giving scientists a real‑time stream of changes across the sky, from brightening stars to newly spotted asteroids. It’s one of the final steps before the Legacy Survey of Space and Time, which will scan the southern sky every night for a decade with unprecedented precision. |
Interview transcript
Terry Gerton Before we jump into the news, please tell us a little bit about the Vera C. Rubin Observatory. Where is it? What’s it designed to do? What’s going on there?
Bob Blum Great, so the NSF-DOE Vera C. Rubin Observatory is a new federally funded observatory. It’s actually a system. It’s distributed all over the world in some sense, but the telescope and the world’s largest digital camera are in Chile, in about the middle of Chile in the region of Coquimbo on a mountain top called Cerro Pachón. And the observatory is just getting started. We have come out of commissioning and the final part of construction late last year, and we are in what I call an early operations optimization phase. We’re getting everything tuned up so that when we get it going, we’ll start our survey of the night sky. And our basic goal is to cover the whole night sky that you can see from here in Chile every few nights and do that repeatedly for 10 years. So we’ll do two things. As we observe every night, and we hit parts of the sky that we’ve observed before, we’ll look at that part of the sky and we’ll take a new image and we will be able to compare that image to the image in the template that we built up before and we’ll be able to identify things that have changed, either they’ve gotten brighter or fainter or maybe some things like solar system objects, asteroids have moved and we’ll report those changes in almost real time. Within a few minutes of taking that image, we’ll report these changes to the scientific community and they can run off right away within minutes if they have access to another telescope and do detailed follow-up of those interesting objects. And there’s a way that we do it. We’re providing about 10 million such changes every night that astronomers can click into a system and decide which of those specific ones they want to concentrate on. So it’s a very massive amount of information coming at them, but there are tools that they can funnel it down to the very few things that any particular group or person is interested in. The other thing that we do by hitting the night sky over 10 years is we continuously add depth to the image of the night sky that we’re building up over those 10 years. So eventually we will go very, very deep, which means we go very, very far in time. And in fact, we call this survey the legacy survey of space and time. That those different aspects of it, the kind of real time aspect and the over time aspect, allow many, many different science cases to be addressed with the same data set. And that data set then is provided to scientists wherever they are or they can access it. They don’t have to come to the telescope. They can access at their convenience over different time scales to do the science that they want to do.
Terry Gerton That’s a fabulous big-picture orientation to this really incredible new facility. I want to start with an announcement you all made. You issued 800,000 alerts in a single night as part of your scaling and break-in period tell us about those alerts and what each one represents and where that is going?
Bob Blum So, one of the first major events in early operations was our announcement of first alerts and that happened a few weeks ago. And the idea was, again, since we’re covering the sky in places that we’ve observed before, we can take the new images, compare them to the old images, and in real time generate a set of objects that have changed. So that’s what the alerts are, they’re the objects that have changed in brightness. That first night was the first night — we’d been testing things for a long time leading up to it — the first night was the first night that we were going to provide those alerts to the scientific community. So we gave them a heads up this was coming. They’d been waiting for it and planning for it. They have their own idea of which alerts are going to be interesting to them. And then we all got ready and we went on sky that night and everything worked wonderfully. And we started producing alerts in our so-called alert stream. And that was this 800,000. That was a very big number but it’s gonna get even bigger over time. We expect that number to get as high as 7 million alerts per night. We’re not there yet. It’ll take us a while to build this template image of the sky so that every time we go to a new place, we have something to compare to. What’s in those alerts? We saw solar system objects that may be changing in brightness. We saw supernovae, new supernova that were going off. You know, as we observed in that night, or continuing to rise in brightness because they had exploded a few nights before. We saw variable stars. In fact, the very first alert that anyone saw in the public science community that came out, it just happened to be the one that was analyzed first and put out in our stream. And then available on a webpage for people to look at, was a star that changed in brightness. It went down in brightness. So, the prior observation had it at a certain brightness level and when we observed it that night, it had gotten fainter, so this was a variable star. I should say that we have tremendous help from our community to make all this happen. These alerts, we produce them, we take the images that result in the comparison, which it results in the set of objects at every image, thousands in every image that we take throughout the night. But then we send them out in what we call a stream. It’s actually very similar to streaming a movie. It’s like Rubin Observatory is Netflix streaming the movie out to the public, in this case our scientific community and instead of a TV or Netflix subscription, there are several groups that have a subscription to our stream And we call those groups brokers. They broker the stream. So this is a place where community scientists can come in to a web interface and say, I want to see alerts that happen in this part of the sky, or maybe even associated with a known galaxy, or have this certain type of characteristics that are typical of what a supernovae might look like, or they’re in this filter or that filter. Or maybe it’s moving objects. I want see alerts of things that have moved across the sky since the last time we were there. And so the community can connect to these brokers and get the actual alert that they’re interested in and then maybe they’re following it over time or maybe they want to go right there that night. It’s a super exciting new supernova and they need to get on it with another big telescope, and so they can follow it in more detail as Rubin goes off and does something else. I should say that we do this on a cadence of every 30 seconds. We take about 30-second images, and then by the time we move to the new place, maybe 40 seconds have gone on. So every 40 seconds, we’re sending an image to our data facility in California. So we’re in Chile, so 10,000 miles away. We have a high bandwidth network that’s dedicated to our operation that’s just, every night as we take an image, it goes up to California. We get those images there in about 10 seconds. And then we process them. So after we’ve taken an image on sky, it’s only about a couple of minutes before the community has the information, the location on the sky, something about brightness, and they can go off and start doing science within a few minutes of us having taken that image. And we just do that over and over, every night for 10 years.
Terry Gerton I’m speaking with Dr. Bob Blum. He’s director for the Rubin Observatory operations. What has been the initial response of the scientific community to those early pictures? Anything surprising pop up there?
Bob Blum I think they’re still digesting it. And so I know that they’ve gone off and that different groups are indeed following up some of the alerts that we’ve seen. So the first response was, this is amazing. We’re so excited. We’re happy to be engaging finally. This project has been in development from its various early stages for more than two decades. And so the last few years, it’s gotten really exciting, everything coming together here in Chile and everything in our data facility in California. By the way, we have other professionals working on our data management system around the world. So a very big community all around the World and our scientific community been with us the whole time thinking about it and getting ready for it. And so that first night when they actually saw it come together live, right on schedule, right on cue, and they could actually go and take the data and either start analyzing it or go off to another telescope. There was just really tremendous excitement. Now, we’re still just starting. We’re still optimizing things. We’re not quite ready to start our big survey for real yet, but the alert stream was the first part of this. And everywhere from us to our scientific community and the brokers in between that are providing the alerts to the community. We’re learning a lot even in the last few weeks as we turned everything on. So 8 million alerts that first night was a big one and we’re seeing how everything worked and we are making tweaks to the things that didn’t work as well as they should have and noting the things that are working well. And so we’ll go forward. In the next period, we’re actually going to tune down the number of alerts that we’re going to be sending out, and that’s just because we’ll hit the natural frequency of places on the sky that we currently have template images and it will take us getting into the survey and covering the sky systematically to really build up the templates before we have the full alert stream. I mentioned earlier 7 million a night at some point down the road. That’ll take us a while to get there so that we have the full sky coverage and we can do the comparison anytime we go. Everyone had a great first taste of what it’s like, and now they can go back out and work on things and make things better as we start to steadily build up this alert stream and get toward the start of the survey.
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