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The Gaia space telescope has measured the acceleration of the Solar System as it orbits the center of our Milky Way.
The movement of the Solar System in relation to the stars agrees with the results of Finnish astronomers in the 19th century.
Additionally, Gaia observing data improves satellite navigation. Finnish researchers are participating in this massive effort, which results in a three-dimensional mapping of our galaxy, to be completed in 2024.
Today, December 3, 2020, the European Space Agency (ESA) published observation data from the Gaia telescope (Gaia Early Data Release 3 or EDR3), in continuation of the DR1 and DR2 versions of the years 2016 and 2018. Gaia accumulates data precise knowledge about, for example, the stars of the Milky Way, the distant extragalactic quasars and the asteroids of our Solar System.
Quasars are bright, star-like objects that help determine the orientation of planet Earth in space. With the help of its precise positions measured by Gaia, a new high-precision reference system can be constructed to define the positions of stars, objects in the Solar System, and also satellites.
“The knowledge accumulated by Gaia affects the accuracy of satellite navigation in the future. The positions of the satellites and the orientation of the Earth in space are determined in a reference frame linked to the directions of quasars. The accuracy and state-of-the-art frames of reference are critical for precision in navigation, “says Professor Markku Poutanen from the Finnish Geospatial Research Institute FGI, National Land Survey of Finland.
Precise observations of quasars resulted, for the first time, in a successful calculation of the acceleration of the Solar System.
“The acceleration of the Solar System towards the center of the Milky Way, measured by Gaia, is (2.32 ± 0.16) x 10-10 m / s2, or approximately two billionths of the gravitational acceleration caused by the Earth on its surface ”, sums up astronomy professor Karri Muinonen at the Department of Physics at the University of Helsinki, also a research professor at the Finnish Geospatial Research Institute FGI.
Gaia in asteroid research
Gaia’s data processing is carried out within the European DPAC (Data Processing and Analysis Consortium) network with more than 300 researchers. Solar System researchers at the University of Helsinki are involved in processing Gaia data in several different ways.
“We are responsible for the daily calculation of the orbits of the asteroids discovered by Gaia. Based on these calculations, the follow-up observations from the ground are organized”, describes Muinonen.
“Prior to data release, we participated in the validation of Gaia’s observations of the positions, brightness, and spectra of the asteroids. Our research with the Gaia data focuses on the asteroid orbits, rotation periods and the orientations of the poles, the masses, the shapes and the structural and compositional properties of the surface. In calculating the collision probabilities of near-Earth asteroids, the precision of the reference frames is completely central ” Muinonen continues.
Gaia’s asteroid observations were published in DR2 in spring 2018 (14,099 asteroids). At the next launch of DR3 in spring 2022, there will be position and brightness data for tens of thousands of asteroids, and for the first time, asteroid spectra will also be published.
Years of work and billions of stars
EDR3 data has been collected by Gaia since the end of July 2014. The data includes, for example, position and brightness data for 1.81 billion stars and color data for 1.55 billion stars from the period of 34 months. Additionally, the data more than triples the number of quasars observed for precise reference frames to 1.61 million.
EDR3 is a notable improvement, in terms of numbers and precisions, compared to previous versions. The most recent version hints at the gigantic nature of the upcoming DR3 release in spring 2022 and the final DR4 release after 2024.
Gaia systematically observes astronomical objects at the so-called L2 Lagrange point, about 1.5 million kilometers from Earth in the anti-sun direction. Gaia observes about two billion stars with an accuracy, at best, of a hundred millionths of a degree. The result will be a three-dimensional map of our galaxy.
Stellar movement in the future
Based on data from Gaia, the researchers have modeled the motion of stars in the Milky Way. They have produced an animation of the movement of 40,000 randomly selected stars in the sky 1.6 million years into the future.
“In the animation, the short and long trails describe changes in stellar positions with 80,000 years. The former are mainly related to distant stars, while the latter are due only to nearby stars. From time to time, the short trails they expand to long trails and long trails shrink to short. This is also related to the changing distances of the stars, “says Muinonen.
At the end of the animation, it appears that the stars are removed from the left and collected on the right. This is due to the movement of the Solar System in relation to the stars. A similar phenomenon can be seen when moving from the center of a forest islet to its limit: the trees in the front gradually disappear while they appear to be gathered in the back.
“This shows the average motion of the Solar System relative to the surrounding stars. From a Finnish point of view, it is intriguing that the motion documented by Gaia agrees with the pioneering research on the motion of the Solar System by Friedrich Wilhelm August Argelander. (1799). -1875) in the 19th century at the Helsinki Observatory “, concludes Muinonen.
Argelander was the first astronomer to unequivocally calculate the direction of the Solar System’s motion in space. He worked at the Observatory of the University of Helsinki, then at the Imperial Alexander University. He had made the observations at the Turku Observatory in 1827-1831 before the observatory moved to Helsinki. In Helsinki, he compiled the stellar catalog entitled “DLX stellarum fixarum positiones mediae ineunte anno 1830” which, as the title says, included the precise positions of 560 stars.
The movement of quasars is actually the movement of the Solar System.
More precisely, the apparent stellar currents include information about the motion of the stars and the Solar System over the center of the Milky Way. Observations of the Gaia quasar allow us to determine the acceleration related to this orbital motion.
Gaia has measured the apparent motions of quasars in the sky. These motions are minuscule, about one thousandth of the motion of stars 3000 light years from us. The apparent current of quasars is directed towards the center of the Milky Way, that is, in the direction that the acceleration of the Solar System points. Gaia, in essence, has measured the absolute motion of the Solar System in relation to the distant universe. This motion is derived from the gravitational forces of the Milky Way and all other objects in the universe.
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Animation: the predicted movement of the stars across the sky. (ESA and Gaia DPAC) https://youtu.be/cEsfqFDSpm0
Read more:
Gaia EDR3 Data Release (3. 12. 2020), Home Page:
https://www.cosmos.esa.int/web/gaia/early-data-release-3
http://www.esa.int/Science_Exploration/Space_Science/Gaia
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