Image credit: ESA / Gaia / DPAC
How far is that star? Despite enormous advances in technology, astronomers have always had problems with the basics of celestial geography.
That ended today when the European Space Agency (ESA) launched its long-awaited Gaia Archive that reveals the distances and exact movements of the 1,300 million stars closest to our solar system, plus data for hundreds of thousands more Astronomy has changed forever.
Why, can you ask? Using the exact positions, colors, movements and brightness of the stars, ESA astronomers have been able to create a 3D map of the Milky Way that accurately shows how far the stars form us, but also a lot about their nature and how they are moving around our galaxy.
Gaia also mapped the appropriate movement of 14,000 asteroids in our solar system revealed how fast seven million stars move towards or away from us, and mapped the orbits of 75 globular clusters and 12 dwarf galaxies that orbit the Milky Way.
How important is Gaia's information?
A satellite that for almost five years has been anchored in an orbit of the sun about 1.5 million kilometers from Earth, the ESA Gaia space observatory of € 750 million (US $ 915 million) has been in A mission to produce a highly detailed star chart of our Milky Way and its neighboring galaxies that is 10,000 times more detailed than we had before.
"Gaia is astronomy at its best," says Fred Jansen, manager of the Gaia mission at ESA. "Scientists will be busy with this data for many years, and we are ready to surprise us with the avalanche of discoveries that will unlock the secrets of our Galaxy."
Astronomers know a lot about star formation in general, and a lot about some individual stars. However, they have always had trouble determining exactly how far they are from us and how they move.
Stars look more or less the same in the night sky, but differ in brightness.
A star could be brighter because it is very close, while another could be bright because it is far away, but it is much bigger.
"Gaia is spinning in the sky making a big circle every six hours, and she turns and covers the sky every two months," said Günther Hasinger, Science Director of ESA. "In the five-year mission we will get 29 images of the whole sky."
3D Map of Gaia from the Milky Way
The new data includes positions and brightness for almost 1.7 billion stars, and distances, own movements and colors for 1.3 billion of them.
"It is not a photograph, it is made of the positions of 1.3 billion stars," said Anthony Brown, Gaia Data Analysis and Analysis Consortium at the University of Leiden, of the first accurate map of our galaxy.
"I should download the high resolution version of ESA and go to a dark place and study it."
In the image it is possible to see the Milky Way plane and its dust bands and more than one billion stars. "It's so high resolution that every point we have distance," said Brown.
What is astrometry?
Gaia stands for Global Astrometric Interferometer for Astrophysics. Astrometry is the science of measuring the positions and movements of stars.
The main problem is that it is very difficult to study the distance between two objects when you are in one of them. Fortunately, the Earth travels around 584 million miles / 940 million km in a year in its sun orbit.
So, astronomers measure exactly where a star appears to be in the night sky twice, six months apart, so they get a measurement from two different places in space. Knowing that the distance from Earth to the Sun is always more or less the same, astronomers then use triangulation.
The closer the star is, the more it will move. This is called stellar parallax.
However, it only really works for the stars that are close to us. Then, astronomers have sent several satellites into space to take measurements from greater distances.
The most famous was Hipparcos (named for the founder of trigonometry), which spent three and a half years at the end of the 1990s accurately measuring the positions of 118,000 stars, and obtaining a general position of 2.5 millions.
The Hipparcos catalog is still used to point terrestrial telescopes and to navigate spaceships. The scope of Gaia is much wider than Hipparcos, and its technology is much more precise. His catalog of a billion stars is starting today the final star catalog, if it was not yet.
What technology does Gaia use?
The instruments of Gaia are thousands of times more sensitive than those of Hipparcos. It is capable of detecting stars up to magnitude 20, which is about 400,000 times weaker than the human eye can see.
Flying in Gaia is a video camera – the largest astronomical camera ever built – and a pair of telescopes that cross the entire sky as the satellite rotates slowly.
The light they collect is channeled to three instruments, and their astro-metric detector records stars when They cross their f
ield of vision, calculating positions, appropriate movement and parallax.
Meanwhile, Gaia's radial velocity spectrometer supports how quickly a star moves closer or farther from Earth, and its photometric instrument collects data on the color and brightness of each star. Gaia is filming each star 70 times.
More work to be done
We now know our place in the Milky Way with unprecedented precision. With Gaia's data, astronomers will be creating models of how the stars will move exactly, and have moved, essentially rewinding and advancing rapidly to unlock the development of the Milky Way.
But no matter how advanced Gaia appears, it's just the beginning. The data published today took 22 months to compile and represents only 50% of the total data of the official five-year mission.
And while the Milky Way is 100,000 light-years across, Gaia has only been able to see up to 8,000 light-years.
Scientists hope to extend the mission for at least two years, and possibly until 2024, to obtain even more accurate measurements.
"1.7 billion is only about 1% of the stars in the Milky Way," said Brown. Only 180 billion (more or less) to go …