![]() The Gaia photometric data is unique in many ways: it represents a high resolution (currently about 0.5 arcsec, but 0.2 arcsec is possible) homogeneous all-sky survey, something that is not possible to achieve with ground-based photometry, and it is doing so at a close to mmag level accuracy. It covers broad band photometry in a “white”, “red” and “blue” channel, and low-resolution dispersion spectra for the red and blue channels. The potential of the proper motions shows in the picture above: significant systematics in proper motions, reflecting the solar motion, are now well detected, even at 1 kpc distance.Ī crucially important element of the Gaia data releases is the photometry, prepared and delivered by the IoA as part of the UK participation in the Gaia data processing. Radial velocities for many of the stars are another Gaia data product. The impact of these improvements in the astrometric data has been demonstrated in papers accompanying Gaia EDR3, in particular on the LMC/SMC, where multiple populations can now be distinguished in proper motion patterns linked to different age stellar populations, and in the census of the 100 pc sphere around the Sun, where the full 6D phase space can be studied for over 330000 stars. For the next, 4 th Gaia data release, which is to cover 66 months of data, a further improvement in proper motion accuracies by a factor 2.7 can be expected. The improvements in the proper motion accuracy with respect to the 2 nd Gaia data release stems from the longer time span covered, as proper motion accuracies improve with the length of the time span to the power 1.5. A provisional algorithm is provided that significantly reduces systematics in the parallax zeropoint. Systematic errors in the parallaxes have been investigated in great detail, and tend to be at a level of 10 to 20 micro arcsec, with dependencies on brightness and position on the sky. The astrometric data in Gaia EDR3 are characterized by parallaxes with precisions improved by on average a factor 1.5, and proper motions improved by on average a factor 2 with respect to the 2 nd release that took place 2.5 years ago. Following the success of the previous Gaia data release, this release is expected to make an even bigger impact on an even wider range of topics in astrophysics, as reflected in the already very high number of papers using, and depending on, the Gaia data, and similarly high number of citations to many of these papers. ![]() ![]() Gaia EDR3 delivers data for just over 1.8 billion sources. This includes the astrometry and broad-band photometry that will also be part of the complete 3 rd Gaia data release, scheduled for the first half of 2022, and which will contain in addition a wide range of derived products such as variability investigations and astrophysical parameters. On December 3, 2020, ESA presented the first part of the 3 rd Gaia data release (Gaia Early Data Release 3, Gaia EDR3). Image prepared by Anthony Brown and Amanda Smith. The pattern reflects the motion of the Solar System within our Galaxy. The lines indicate the average present day direction of motion of the stars. The image shows the average motion of stars located at 1000 pc from the Sun.
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