Sorting out the evolution of our home galaxy, the Milky Way, is a challenge similar to mapping the human genome, according to the European Space Agency (ESA). ESA’s galaxy charter, Gaia, takes trillions of measurements of 2 billion of the brightest stars in the sky. Here we look at what it takes to remove these measurements to reveal the galaxy’s secrets.
June 13, the Gaia Data Processing and Analysis Consortium (DPAC), a collaboration between 450 European astronomers and supporting engineers galaxen-mapping endeavor, released what DPAC chairman Anthony Brown described as “the richest set of astronomical data ever published.”
To create the 10-terabyte directory of compressed data, DPAC computers had to take in 940 billion observations of 2 billion of the brightest light sources in the sky, said Brown, an astronomer at Leiden University in the Netherlands, at an ESA press conference in June. 13.
The data, captured by Gaia between June 2014 and June 2017, contained information on the exact positions and movements of 1.5 billion stars in the sky; details of ages, temperatures and brightness for about half a billion of these stars; and detailed chemical compositions of millions of them.
It took five years for data to pass through the sophisticated computational pipeline of validation, calibration and analysis procedures, involving six supercomputer centers in six European countries. It would take a thousand years for a single (and quite powerful) personal computer to process the amount of data, says Gonzalo Gracia, DPAC project coordinator for data processing, to Space.com.
As of 2022, Gaia’s main database contains 1 petabyte of data, Gracia added, which corresponds to the data capacity of 200,000 DVDs. To date, the telescope has made over 100 measurements of every single one of the 2 billion light sources it sees.
“Every day, Gaia sends us between 20 and 100 gigabytes of data,” Gracia said. “It may not seem like much if you compare it to the bandwidth you have at home, but we’m talking about a satellite that is 1.5 million kilometers [930,000 miles] away from the earth. “
The journey of the data
From Gaia’s vantage point at Lagrange Point 2, a stable point in the solarEarth system where the gravitational pulls of the two bodies are in balance, the spacecraft observes the cosmos while being shielded from Solars glare.
Three ESA deep space antennas (one near Madrid; Malargüe, Argentina; and New Norcia, Australia) receive data collected by the spacecraft’s two telescopes and other instruments. From these ground stations, the measurements on conventional internet lines go to the European Space Operations Center in Darmstadt, Germany, for basic checks, before the data is sent to the Agency’s Science Operations Center in Madrid.
“That’s when we do the first round of processing,” Gracia said. “We do some initial calibrations and run the data through a software to assess the satellite’s health. This happens during the first hours after the data is received.”
Then things start to get complicated. A data processing center at CNES, the French space agency, in Toulouse, scans the amount of data for fast-moving objects in Solar system: asteroids and comets which may be on a collision course with Earth.
“They have a pipeline that detects these objects and checks if they are already known,” Gracia said. “If they are not known, they leave the solar system object community in the world, which can do the follow-up observation and find out what the object is about and what its orbit is.”
Gaia is quite effective in monitoring asteroids and may even be able to see some that are not visible from Earth. The mission’s data release on June 13 contained information on detailed orbits for 60,000 space rocks in the solar system. In addition, Gaia measured the light spectra of these space rocks and revealed their chemical composition. Previously, astronomers knew the detailed chemical compositions of only 4,500 asteroids.
Separately, a team in Cambridge, England, compares new brightness measurements from Gaia with data previously acquired. Significant changes in the brightness of stars are always a cause for excitement, which they may indicate supernovorexplosions that occur when massive stars die before collapsing into black holes or neutron stars.
Sometimes dark distant stars and galaxies can temporarily light up through microlensingan odd phenomenon that occurs when an extremely massive object comes between the faint star and the observer, its powerful light bending seriousness acts as a magnifying glass. Gaia, who scans the entire sky every two months, sees it all.
Again and again
Meanwhile, the rest of the consortium is carrying out what Gracia calls “cyclical processing”: endless rounds of remelting, validating and analyzing data to extract the most accurate information astronomers can use to create exact maps of The Milky Way the galaxy and model its life to the past and future. Several thousand servers running tens of thousands of core processors are involved in the operation.
“We have to process the data several times,” Gracia said. “We process it, we give it to the scientists for control, and then we have to adjust our calibrations, our algorithms; we have to improve them every time.”
The data sets are also interdependent. For example, without information on the exact positions of the observed objects, data on brightness changes or the movements of asteroids would be useless.
“We mainly have information about the amount of photons that hit the Gaia telescope, and from their position in the window we derive the positions in the sky,” Gracia said. “This is done in Barcelona, where we produce this astrometric information for all sources in the sky. This is input for basically all other processing that we do. It takes a lot of time to do all that and to do it with a sufficient amount of data to ensure that the data is indeed of the highest quality. “
This amount of processing is the cause of the delay between the collection of data and its release. Gaia was launched in December 2013, but the astronomical community did not get hold of the first batch of data until September 2016. The second data release followed in April 2018. Data dumping on June 13 was preceded by a partial early release in December 2020. Each new catalog increases the precision of data and the amount of information available on each of the 2 billion light sources that the telescope sees. Even though the mission is already in its ninth year, there is no stopping the 450 researchers and engineers at DPAC.
While the world’s Milky Way scientists unpack the gifts from the June 13 data release and look for evidence of the galaxy’s dynamic life, Gracia and his colleagues are already busy working on the next data dump, which promises to unleash Gaia’s potential to discover planets around distant stars. . Thousands of new finds are expected to enrich the existing ones exoplanet catalog as DPAC scientists train their algorithms to detect the characteristic mild dimming of a star caused by a planet orbiting in front of its disk.
“We started processing data for the fourth cycle two years ago and are already planning the fifth cycle,” Gracia said. “It really is nonstop.”
#sort #development #Milky #big #data #astronomy