The European space mission Gaia has created an unprecedented amount of new, improved and detailed data on almost two billion objects in the Milky Way galaxy and outer space. Monday’s edition of Gaia Data 3 revolutionizes our knowledge of the solar system and the Milky Way and its satellite galaxies.
The European Space Agency’s ESA Gaia space mission is building an ultra-precise three-dimensional map of our Milky Way galaxy, observing nearly two billion stars, or approximately one percent of all stars in our galaxy. Gaia launched in December 2013 and has been collecting scientific data since July 2014. On Monday, June 13, ESA published data on Gaia in Data Release 3 (DR3). Finnish researchers were heavily involved in the release.
Gaia data allow, for example, the extraction of the orbits and physical properties of asteroids and exoplanets. The data helps to reveal the origin and future evolution of the solar system and the Milky Way and helps to understand the evolution of the stellar and planetary systems and our place in space.
Gaia rotates around its axis slowly for about six hours and consists of two optical space telescopes. Three scientific instruments allow accurate determination of stellar positions and velocities, as well as spectral properties. Gaia is located about 1.5 million kilometers from Earth in the direction of the Sun, where it orbits the Sun with the Earth near the so-called Lagrange point Sun-Earth L2.
Gaia DR3 on June 13, 2022 was significant in astronomy. About 50 scientific papers have been published with DR3, nine of which are dedicated to highlighting the extremely significant potential of DR3 for future research.
New DR3 data include, for example, the chemical composition, temperatures, colors, masses, luminances, ages and radial velocities of stars. DR3 includes the largest binary star catalog for the Milky Way, more than 150,000 objects in the solar system, mostly asteroids, but also planetary satellites, as well as millions of galaxies and quasars beyond the Milky Way.
“There are so many revolutionary achievements that it is difficult to determine the most significant progress. Based on Gaia DR3, Finnish researchers will change the concept of asteroids in our solar system, exoplanets and stars in our Milky Way galaxy, as well as galaxies themselves, including the Milky Way and surrounding satellite galaxies. Returning to our home planet, Gaia will create an ultra-precise frame of reference for navigation and positioning, “said Academy Professor Carrie Muinonen of the University of Helsinki.
Gay and asteroids
The tenfold increase in the number of asteroids reported in Gaia DR3 compared to DR2 means that there is a significant increase in the number of close encounters between asteroids detected by Gaia. These close encounters can be used to estimate the mass of the asteroid and we expect a significant increase in the number of asteroid masses that will be obtained using Gaia DR3 astrometry, especially when combined with astrometry obtained from other telescopes .
Conventional calculation of the asteroid’s orbit assumes that the asteroid is a point object and its size, shape, rotation, and light scattering properties are not taken into account. However, the astrometry of the Gaia DR3 is so accurate that the angular displacement between the center of mass of the asteroid and the center of the area illuminated by the Sun and visible by Gaia must be taken into account. Based on Gaia DR3, the displacement is certified for asteroid (21) Lutetia (Figure 2). ESA Rosetta’s space mission imaged Lutetia during a flight on July 10, 2010. Using the Rosetta Lutetia imagery and terrestrial astronomical observations, a period of rotation, orientation of the pole of rotation and a detailed model of the shape were obtained. When physical modeling is included in the orbital calculation, systematic errors are eliminated and, contrary to conventional calculations, all observations can be included in the orbital solution. Therefore, Gaia’s astrometry provides information about the physical properties of asteroids. These properties must be taken into account when using physical models or empirical models of errors in astrometry.
Gaia DR3 includes spectral observations for the first time. The spectrum measures the color of the target, which means the brightness at different wavelengths. One particularly interesting feature is that the new version contains about 60,000 spectra of asteroids in our solar system (Figure 3). The spectrum of asteroids contains information about their composition and therefore about their origin and the evolution of the entire solar system. Before Gaia DR3, there were only a few thousand asteroid spectra, so Gaia will multiply the amount of data by more than an order of magnitude.
Gaia and exoplanets
Gaia is expected to detect up to 20,000 giant exoplanets by measuring their gravitational effect on the motion of their host stars. This will make it possible to find almost all Jupiter-like exoplanets in the solar quarter in the coming years and will determine how common the solar system-like architectures are. The first such astrometric discovery of Gaia was a giant exoplanet around Epsilon Indy A, which corresponds to the nearest Jupiter-like exoplanet in just 12 light-years. The first such detections are possible because the acceleration observed in radial velocity studies can be combined with Gaia motion data to determine orbits and planetary masses.
Gaia and galaxies
Gaia DR3’s microarc resolution provides accurate measurements of star motion not only in our own Milky Way galaxy, but also for the many satellite galaxies that surround it. From the motion of the stars in the Milky Way itself, we can accurately measure its mass, and together with the proper motion of the satellites, we can now pinpoint their orbits. This allows us to look at both the past and the future of the Milky Way galactic system. For example, we can find out which of the galaxies that orbit the Milky Way are real satellites and which are just passing through. We can also study whether the evolution of the Milky Way corresponds to cosmological models, and in particular whether the orbits of the satellite correspond to the standard model of dark matter.
Gay and reference frameworks
The International Celestial Reference Framework, ICRF3, is based on the position of several thousand quasars, determined by very long basic interferometry (VLBI) at radio wavelengths. ICRF3 is used to obtain the coordinates of celestial objects and to determine the orbits of satellites. ICRF3 quasars are also fixed points in the sky that can be used to determine the exact orientation of the Earth in space at any time. Without this information, for example, satellite positioning would not work.
Gaia data contains about 1.6 million quasars that can be used to create a more accurate celestial reference frame in visible light, replacing the current one. In the future, this will affect the accuracy of both satellite positioning and measurements of satellites exploring the Earth.