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Now You Can Join the Search for Killer Asteroids

A Hawaii observatory just put the largest astronomical data trove ever online, making it free and accessible so anyone can hunt for new cosmic phenomena.

If you want to watch sunrise from the national park at the top of Mount Haleakala, the volcano that makes up around 75 percent of the island of Maui, you have to make a reservation. Being at 10,023 feet, the summit provides a spectacular—and very popular, ticket-controlled—view.

Just about a mile down the road from the visitors center sits “Science City,” where civilian and military telescopes curl around the road, their domes bubbling up toward the sky. Like the park’s visitors, they’re looking out beyond Earth’s atmosphere—toward the sun, satellites, asteroids, or distant galaxies. And one of them, called the Panoramic Survey Telescope and Rapid Response System, or Pan-STARRS, just released the biggest digital astro data set ever, amounting to 1.6 petabytes, the equivalent of around 500,000 HD movies.

From its start in 2010, Pan-STARRS has been watching the 75 percent of the sky it can see from its perch and recording cosmic states and changes on its 1.4 billion-pixel camera. It even discovered the strange 'Oumuamua, the interstellar object that a Harvard astronomer has suggested could be an alien spaceship. Now, as of late January, anyone can access all of those observations, which contain phenomena astronomers don’t yet know about and that—hey, who knows—you could beat them to discovering.

Big surveys like this one, which watch swaths of sky agnostically rather than homing in on specific stuff, represent a big chunk of modern astronomy. They are an efficient, pseudo-egalitarian way to collect data, uncover the unexpected, and allow for discovery long after the lens cap closes. With better computing power, astronomers can see the universe not just as it was and is but also as it's changing, by comparing, say, how a given part of the sky looks on Tuesday to how it looks on Wednesday. Pan-STARRS's latest data dump, in particular, gives everyone access to the in-process cosmos, opening up the "time domain" to all earthlings with a good internet connection.

Pan-STARRS, like all projects, was once just an idea. It started around the turn of this century, when astronomers Nick Kaiser, John Tonry, and Gerry Luppino at Hawaii’s Institute for Astronomy suggested that relatively “modest” telescopes—hooked to huge cameras—were the best way to image large skyfields.

Today, that idea has morphed into Pan-STARRS, a many-pixeled instrument attached to a 1.8-meter telescope (big optical telescopes may measure around 10 meters). It takes multiple images of each part of the sky to show how it’s changing. Over the course of four years, Pan-STARRS imaged the heavens above 12 times, using five different filters. These pictures may show supernovae flaring up and dimming back down, active galaxies whose centers glare as their black holes digest material, and strange bursts from cataclysmic events. “When you visit the same piece of sky again and again, you can recognize, ‘Oh, this galaxy has a new star in it that was not there when we were there a year or three months ago,” says Rick White, an astronomer at the Space Telescope Science Institute, which hosts Pan-STARRS’s archive. In this way, Pan-STARRS is a forerunner of the massive Large Synoptic Survey Telescope, or LSST, which will snap 800 panoramic images every evening with a 3.2-billion-pixel camera, capturing the whole sky twice a week.

Plus, by comparing bright dots that move between images, astronomers can uncover closer-by objects, like rocks whose path might sweep uncomfortably close to Earth.

That latter part is interesting not just to scientists but also to the military. “It’s considered a defense function to find asteroids that might cause us to go extinct,” White says. That's (at least part of) why the Air Force, which also operates a satellite-tracking system on Haleakala, pushed $60 million into Pan-STARRS’s development. NASA, the state of Hawaii, a consortium of scientists, and some private donations ponied up the rest.

But when the telescope first got to work, its operations hit some snags. Its initial images were about half as sharp as they should have been, because the system that adjusted the telescope’s mirror to make up for distortions wasn’t working right.

Also, the Air Force redacted parts of the sky. It used software called Magic to detect streaks of light that might be satellites (including the US government's own). Magic masked those streaks, essentially placing a dead-pixel black bar across that section of sky, to “prevent the determination of any orbital element of the artificial satellite before the images left the [Institute for Astronomy] servers,” according to a recent paper by the Pan-STARRS group. The article says the Air Force dropped the requirement in December 2011. The magic was gone, and the scientists reprocessed the original raw data, removing the black boxes.

The first tranche of data, from the world’s most substantial digital sky survey, came in December 2016. It was full of stars, galaxies, space rocks, and strangeness. The telescope and its associated scientists have already found an eponymous comet, crafted a 3D model of the Milky Way’s dust, unearthed way-old active galaxies, and spotted everyone’s favorite probably-not-an-alien-spaceship, ’Oumuamua.

The real deal, though, entered the world late last month, when astronomers publicly released and put online all the individual snapshots, including auto-generated catalogs of some 800 million objects. With that data set, astronomers and regular people everywhere (once they've read a fair number of help-me files) can check out a patch of sky and see how it evolved as time marched on. The curious can do more of the “time domain” science Pan-STARRS was made for: catching explosions, watching rocks, and squinting at unexplained bursts.

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