The end of the universe to the left - the Gaia spacecraft was launched to map the Milky Way

A European spacecraft is supposed to map the Milky Way with unprecedented precision

In Greek mythology, Gaia is the great mother who gives birth to the earth, the sky and the entire universe. The name is very appropriate for a spacecraft that is supposed to map the universe with a scope and level of precision that were unmatched. After about a decade of building the spacecraft, and an investment of about 2 billion euros. This morning, Thursday, the Gaia spacecraft was successfully launched on a Russian "Soyuz" rocket from the space base in French Guiana.

Advanced equipment

The spacecraft, which weighs about 2,000 kg and has a diameter of about 10 meters, is equipped with a very sophisticated telescope, actually a double telescope, which also contains an instrument for measuring the intensity of light with extremely high sensitivity. The telescope is also connected to a camera with a photo quality of one billion pixels (about 100 times that of a sophisticated smartphone camera). This equipment will allow her to photograph objects thousands of meters fainter than the human eye is able to distinguish them, and to determine with great precision the position of the most distant stars. Additional instrumentation in the spacecraft allows it to measure the wavelengths of the light emitted by stars (which can provide information on their chemical composition, speed and direction of movement) as well as the speed of rotation of stars around themselves. Unlike the usual space telescopes, it will not orbit the Earth, but rather around the Sun, in an orbit slightly wider than the Earth's (about one and a half million kilometers from us). During its five years of operation, the spacecraft is supposed to photograph each of the billion stars approximately 70 times - that is, on the order of 40 million photographs a day. This huge amount of data will be analyzed by a team of no less than 500 scientists from all over Europe - not only astrophysicists, but also many computer and software professionals, who are supposed to provide tools to deal with the huge amounts of information.

The depth of the map

The fact that Gaia will photograph each star many times, from different points along its path, will allow researchers to determine not only its location on the map of the sky, but also its distance from us, and make the map three-dimensional. "We have never had a mapping of such a quantity of stars and with such a level of accuracy," says Prof. Shai Zucker, from the Department of Geophysics and Atmospheric and Planetary Sciences at Tel Aviv University, one of the researchers who will participate in the Gaia data analysis. "As is the way of measurements in physics, when we reach precision levels that are orders of magnitude better than what was in the past, we usually encounter new surprises, beyond what we originally wanted to learn and understand. It's a great thrill for the surprises that await us when we reach these precisions."

solving puzzles

The in-depth mapping of the Milky Way is not intended for navigation needs in its spaces. With the technologies that exist today, we can only dream of traveling such great distances. Accurate mapping of the sky can certainly help navigation systems of satellites and spacecraft, but Gaia's observations mainly deal with basic science, and the researchers hope that the new knowledge about the Milky Way will shed new light on the history of our galaxy, on the ways of its formation and perhaps also on its future. In any case, the huge amount of data that Gaia is supposed to collect, can provide infinitely more information about the mapping itself.

First, the researchers expect to discover with the help of the extensive observations many more celestial bodies that have not yet been identified, from comets and asteroids, to distant galaxies and intense stellar explosions (supernovae). The researchers expect that the very precise measurements could also provide additional confirmation to the theory of general relativity, in which Einstein predicted, among other things, that the gravity of stars may deflect light rays from their orbits. The most optimistic among scientists also fantasize about a solution - or at least a hint of a solution - to the dark energy puzzle: our universe is expanding at an ever-increasing rate, even though according to all the data we have regarding the amount of matter in the universe, it should actually be contracting. To settle the contradiction, the scientists explain that we only see a tiny fraction of the matter in the universe, and what we don't see (supposedly) they call "dark matter", which is supposed to explain the missing mass, and "dark energy", which is supposed to push the universe to expand. However, beyond this assumption, no one knows the nature of these dark mysteries. Another application of Gaia data may be the discovery of many planets in distant solar systems.

Modesty

As our sun has planets, eight in number, so it turns out that more and more stars in the vastness of the universe have their own planets. In recent years, astrophysicists have identified hundreds of planets in distant solar systems, and the search for them continues even more intensively. The reason these planets are so interesting to us is the hope of finding another life form somewhere in space, and scientists believe that the chances of its existence will be in a place where the conditions on its surface are similar to those of the Earth. The distant planets are almost impossible to detect by direct observation. Even if they are large enough, they are still very small in relation to their sun, and do not emit their own light. Therefore, the main search is carried out by two methods. In one, the rotational speed of a star (ie sun) is measured with great precision. If it has planets, they slightly deviate it from its axis of rotation around itself, and this deviation can be measured, and with it the approximate distance and size of the planet(s) can be calculated. In the other method, which was also used by the "Kepler" space telescope, the light intensity of a certain sun is measured with great precision, and a small periodic decrease in the light intensity is looked for. Such a decrease will occur when the planet passes between us and the sun, and even though we cannot see it, it hides a tiny part of the light from us (the decrease can be one percent, even less). When Gaia's mission began to take shape, Prof. Zucker and his research student (now Dr.) Yifat Dzigan proposed a way to use its data to identify planets by measuring the intensity of light. According to the proposal, stars photographed by Gaia and seen as "suspicious" of having planets, will also be immediately photographed by telescopes from the Earth, and cross-referencing the data will make it possible to locate if indeed there are such planets there. The proposal was accepted, and today the establishment of a kind of "social network" of telescopes around the world, mainly in academic institutions, is being completed. The use of a large network makes it possible to ensure that at any given time it is possible to point a telescope from the Earth in the direction that Gaia is looking at, and to observe this direction for a continuous period of time, even though the Earth is rotating in the meantime. "The more planets we find, the more knowledge we will have about their formation processes, and especially about their frequency," Zucker explains. "This will allow us to better calculate the probability of finding a planet similar to ours, and focus the search for life forms in space."

For a previous article on the subject: Tomorrow, the Gaia spacecraft will be launched into space, which is expected to revolutionize the understanding of the galaxy