The Gaia mission is currently engaged in the meticulous creation of an incredibly precise three-dimensional map encompassing over a billion stars spanning not only our Milky Way galaxy but extending beyond its borders. This ambitious endeavor involves mapping various critical attributes of these celestial objects, including their motions, luminosity, temperature, and composition. The resulting comprehensive stellar census promises to supply the essential data required to confront a vast array of profound inquiries pertaining to the Milky Way’s origin, structure, and evolutionary trajectory.
In this collaborative effort, the European Space Agency (ESA) and the Gaia consortium have unveiled a series of five Focused Product Releases, heralding groundbreaking outcomes. These recent findings serve as a tantalizing glimpse into what will ultimately culminate in the fourth iteration of the Gaia catalog, known as Gaia DR4, expected to be unveiled by the close of 2025.
Since its launch in 2014, the Gaia satellite has been diligently surveying the heavens, charting stars that are a million times fainter than those visible to the naked eye. A significant milestone in astrophysical research, the third iteration of the comprehensive star catalog, Gaia DR3, was published in June 2022. Gaia’s remarkable precision in determining distances, motions, fundamental star parameters, as well as the classification of quasars and precise astrometry of asteroids, has now become an integral part of the daily work and investigations conducted by astronomers worldwide.
Among the highlights of the newly disclosed data is the globular cluster Omega Centauri, housing approximately 10 million densely packed stars that posed a formidable challenge for Gaia’s resolution capabilities. In anticipation of Gaia DR4, various methodologies are under consideration to process data in densely populated and scientifically intriguing regions. The reprocessing of data related to the Omega Centauri cluster has yielded the astrometry and photometry of an additional 526,587 stars located at its core.
While Gaia has observed the same stars on multiple occasions and at various epochs, ESA had hitherto only published averaged measurements. Nonetheless, this approach did not impede Gaia from identifying variable stars, even though attributes such as instant photometry and radial velocities used in the classification process remained unpublished. As we await Gaia DR4, which will offer access to all observations, both epoch-specific and averaged, a partial release of the highest-quality time series data for 9164 Long Period Variables is now available. This resource will assist the scientific community in preparing for the deluge of data that Gaia is poised to deliver in 2025.
The ESA-Gaia spacecraft has conducted repeated observations of an unprecedented number of cool giant stars known as Mira variables, characterized by continuous surface expansions and contractions over extended periods, sometimes exceeding a year. A detailed analysis of Gaia’s spectra enables the precise measurement of surface movements and atmospheric velocities, as evidenced by Doppler shifts in dark spectral lines. This invaluable information enhances our understanding of these unique celestial phenomena.
The interstellar space, often mistakenly regarded as empty, is, in fact, populated by low-density gas composed of atoms, ions, molecules, and dust particles. This interstellar matter plays a pivotal role in the absorption and scattering of light, resulting in a gradual reddening and attenuation of stellar radiation. Additionally, intriguing spectral features known as Diffuse Interstellar Bands emerge in the spectra of stars, attributed to the absorption by complex molecules present in specific interstellar directions. These bands fall within the wavelength range of the Gaia Radial Velocity Spectrometer and are employed to trace their formation within the Milky Way’s disk and spiral arms.
At the extremes of Gaia’s observational range, quasars are detected. Some of these quasars appear in close proximity to massive galaxies and undergo gravitational lensing, an optical phenomenon caused by the bending of light as it passes through the gravitational field of the galaxy. This effect produces a gravitational mirage that can be leveraged to directly estimate the age and expansion rate of the Universe. In recent months, Gaia teams have identified 381 new candidate lensed quasars and mirages, further expanding our ability to investigate these phenomena.
On the opposite end of the distance scale, Gaia has reprocessed data pertaining to 156,764 asteroids. This reanalysis, conducted using 66 months of data instead of the 34 months in Gaia DR3, now covers the complete revolution of most main-belt asteroids around the Sun, significantly enhancing orbit accuracy.
The invaluable contributions of astrophysicists from institutions such as KU Leuven, the Royal Observatory of Belgium, Université libre de Bruxelles, Universiteit Antwerpen, and Université de Liège, supported by the Belgian Federal Science Policy Office (BELSPO) through the PRODEX Programme of ESA, have played a pivotal role in processing and analyzing Gaia data. These efforts have not only yielded new data to complement Gaia DR3 but also serve as a proof-of-concept for several new features to be incorporated in the data analysis pipeline for Gaia DR4, which promises twice the volume of data. These Focused Product Releases offer a critical and informative preview of the vast potential that the fourth edition of the catalog will bring to the forefront of astronomical research.
