Wednesday was the day astronomers said goodbye to the old Milky Way they had known and loved and hello to a new view of our home galaxy.
A European Space Agency mission called Gaia just released a long-awaited treasure trove of data: precise measurements of 1.7 billion stars.
It's unprecedented for scientists to know the exact brightness, distances, motions and colors of more than a billion stars. The information will yield the best three-dimensional map of our galaxy ever.
"This is a very big deal. I've been working on trying to understand the Milky Way and the formation of the Milky Way for a large fraction of my scientific career, and the amount of information this is revealing in some sense is thousands or even hundreds of thousands of times larger than any amount of information we've had previously," said David Hogg, an astrophysicist at New York University and the Flatiron Institute. "We're really talking about an immense change to our knowledge about the Milky Way."
The Gaia spacecraft launched in 2013 and is orbiting our sun, about a million miles away from Earth. Although it has surveyed a huge number of stars, Gaia is charting only about 1 percent of what is out there. The Milky Way contains around 100 billion stars
For 7 million stars, Gaia even has measurements showing their velocity as they move toward or away from the spacecraft. "This is just a fantastic new addition," said Anthony Brown of the Netherlands' Leiden University, with the Gaia Data Processing and Analysis Consortium.
In 2016, Gaia released some initial results but that was just a tease compared with Wednesday's massive data dump. Astronomers around the world have been planning how to attack it for months, knowing that discoveries are just waiting in there for the taking.
"Enjoy it," Antonella Vallenari, another member of the consortium from the Astronomical Observatory of Padua in Italy, said at a news conference as she announced that the data was becoming available.
The European team presented new images of our galaxy based on some initial analyses of the data, along with little movies that simulated what it would be like to fly through the stars. "It's not fake, it's real measurements," Brown said. "We know exactly where the stars are."
Scientists around the world who were watching the event online struggled to take it all in. "This is like massive scientific progress and we were blinked an image," said Jackie Faherty, an astronomer at the American Museum of Natural History, one of more than a dozen astronomers who woke up before dawn and gathered together at the Flatiron Institute in New York City to watch.
Then it was time to play, as the scientists bent their heads over their laptops and tried to download data. Researchers are expecting a slew of discoveries in the coming hours and days, but analyses will go on for years and even decades.
"This is the data we're going to be working on for the rest of my career. Probably no data set will rival this," Faherty said. "It's the excitement of the day that we see it. It's why we were up at 5 a.m. to get here. It's exciting to be around each other and trying to get the data all at once. It's a day we're going to remember."
AILSA CHANG, HOST:
Astronomers have just gotten a brand-new view of our home galaxy, the Milky Way. That's because early this morning, the European Space Agency released an astounding new star map. Scientists immediately started studying it, and they're already making new discoveries. NPR's Nell Greenfieldboyce joined one group of researchers in New York City.
NELL GREENFIELDBOYCE, BYLINE: David Hogg got up before 5 a.m. this morning because he was so excited that today was the day he was going to get precise measurements on 1.7 billion stars.
DAVID HOGG: So for me, it's potentially, really, a life-changing event.
GREENFIELDBOYCE: He's an astrophysicist at New York University. The data he was waiting for comes from a European science mission called Gaia. Gaia is a spacecraft that's orbiting the sun about a million miles from Earth, charting the brightness, motion, color and position of an unprecedented number of stars in our galaxy.
HOGG: We're really talking about an immense change to our knowledge about the Milky Way.
GREENFIELDBOYCE: And the Gaia team was going to release all of this to the public all at once. So Hogg invited dozens of colleagues to join him at the Flatiron Institute in Manhattan. They gathered in a conference room before dawn, watching a live broadcast from Europe as the mission's scientists showed off some of the first images made with the new data.
UNIDENTIFIED SCIENTISTS: Whoa.
GREENFIELDBOYCE: Then Andy Casey from Monash University noticed something.
ANDY CASEY: You can download it already. It's out early.
GREENFIELDBOYCE: He found a way to get the data a few minutes before the official release time. Heads bent over laptops. People started looking at everything from white dwarfs to cosmic dust. Keith Hawkins is from Columbia University. He was looking for hypervelocity stars, stars moving super-fast. Only about 20 had been known, and he quickly used the Gaia data to discover one more.
KEITH HAWKINS: It's a completely new hypervelocity star. I haven't looked anything further - other than its velocity. It's moving at about 600 kilometers per second, which is enormously fast - on the order of - a few million miles per hour, at least.
GREENFIELDBOYCE: How do you feel? Yeah. I mean, there's only 20. So what is it like to find another one?
HAWKINS: Feels good. There's one new one, so I suspect we'll see thousands of new ones discovered within the next few hours.
GREENFIELDBOYCE: Meanwhile, others we're finding weird, unexpected stuff. Adrian Price-Whelan is from Princeton University.
ADRIAN PRICE-WHELAN: I'm sitting here with Ana Bonaca, who's a post-doc at Harvard, and we've been looking at the Gaia data for this stellar stream.
GREENFIELDBOYCE: It's like a stream of moving stars. And what they saw were signs that stars had been forced out of the stream in an odd way.
PRICE-WHELAN: Which could be an indication of an interaction with a dark matter subhalo, which has been never before seen.
GREENFIELDBOYCE: That would be a big deal if it's true.
PRICE-WHELAN: But it's probably wrong (laughter).
GREENFIELDBOYCE: This scene was being repeated all around the world. The European Space Agency said that within the first three hours, the new information had been accessed by more than 4,000 people.
JACKIE FAHERTY: It's exciting to be around each other and trying to get the data all at once.
GREENFIELDBOYCE: Jackie Faherty is an astronomer at the American Museum of Natural History.
FAHERTY: This is the data we're going to be working on for the rest of my career. Probably no data set will rival this.
GREENFIELDBOYCE: She says this is just the first day of what will be years of research, but it's a day they'll always remember. Nell Greenfieldboyce, NPR News. Transcript provided by NPR, Copyright NPR.