"It's like waiting for Christmas," said Vasily Belokurov, an astronomer at Cambridge University in the UK last week. Today, the gifts have arrived: the exact positions, movements, magnitudes and colors of 1.3 billion stars in and around the Milky Way, as tracked by the European Space Agency (ESA)'s € 750 million satellite Gaia Starting to measure in 2013, the positions of stars began and, over time, how they move. On April 25, ESA released Gaia's second dataset, based on 22 months of observations, which is publicly available to provide a precise 3D map of large parts of the galaxy and their movements. "Nothing comes close to what Gaia will release," says Belokurov.
One would think that the galaxy is completely mapped. But much of it is obscured by gas and dust, and it's hard to tell the structure from the solar system's point of view. Not only is Gaia going to explain the spiral structures of the galaxy today, but because the satellite tracks stars, astronomers can rewind the clock and see how the galaxy has evolved over the last 13 billion years – an area known as galactic archeology , With Gaias color and brightness information, astronomers can classify the stars according to their composition and identify the stellar nurseries where different species were born to understand how chemical elements were shaped and distributed.
Gaia is not just about the Milky Way. For Solar System scientists, the new dataset will contain data on 14,000 asteroids. That's a small fraction of the roughly 750,000 known smaller bodies, but Gaia delivers orbit information 100 times more accurately than before, says Gerry Gilmore of the University of Cambridge, who heads the UK department of the Gaia Computing Consortium. This was to help astronomers identify asteroid families and understand their relationship to each other, shedding light on the solar system's past, and how planets emerge from smaller bodies.
For cosmologists, the dataset will improve distance measures to stars of known brightness, such as Cepheid variables, crucial jump stones that allow to build a "distance ladder" to other galaxies – thus calculating the universe's rate of expansion, also known as the Hubble constant can be. And exoplanet hunters expect Gaia will eventually see thousands of stars moving from side to side because of the gravitational traps of Jupiter-sized planets in distant orbits, but these will not occur until the satellite's accuracy improves in later data. "No one in the world knows what we'll find," says David Hogg of New York University, New York City.
The Gaia team released a first catalog in 2016 that contained more than a billion stars only applications for 2 million of them. It was a 'sampler to make people deal with Gaia-type data,' says Gilmore. The 2016 release showed that the Milky Way was larger than previously thought. The first paper to use the data appeared on the arXiv Preprint server the same day. Since Gilmore says, there is an average of one report per day.
This time astronomers are even more equipped with algorithms that can crack the tabular data. Belokurov says that he and his group must track about 50 ideas, including an assessment of mass distribution across the Milky Way and the Large Magellanic Cloud (LMC), a nearby satellite galaxy. Astronomers have long estimated the LMC mass to be around one billion solar masses, but studies have recently suggested that it could be harder. With Gaia data, they may be able to see Milky Way objects being disrupted by the LMC, which would be indicative of their more massive gravitational influence. "There will be a complete science explosion," says Belokurov. "I'm not going to sleep for a week or two."
Hogg is also ready for a heavy Gaia hacking. For the release, he invited colleagues from around the world to gather in New York to work on analyzing the data. He initially plans to design plans that were previously not possible to look for new trends. For example, the graphical representation of color versus brightness for white dwarf stars might elucidate how these stellar remnants change as they cool and eventually become black stellar slags. After the first release of Gaia, "almost every act resulted in a paper," he says.
The 450-member Gaia consortium is already working on a third data release planned for 2020. "There are very clear areas that we can improve," says ESA Project Leader Timo Prusti from the European Space Research and Technology Center in Noordwijk, the Netherlands. For example, in a special short-exposure observation mode, the team wants to return to the brightest stars that saturate the detector. The team also wants to improve the possibilities of stray light on the detector, a problem that only occurred after the start.
Gaia is also unusual because the scientists who work on the mission are not granted exclusivity, the data, a common practice in astronomy. Although the members of the Gaia consortium know exactly how the data is collected and processed, they can not use the data like all the others until after publication for the science. "It's brave and very admirable," says Belokurov.
Gilmore says his teammates have bet on how many newspapers the preprint servers will reach on the first day. Belokurov says: "It's like a festival – the festival of Gaia."