Saturday, June 25, 2022

3612 - GAIA Space Telescope - data is pouring in?

  -  3612 -   GAIA  Space Telescope  -  data is pouring in?   The “Gaia space mission” will make the largest, most precise three-dimensional map of our Milky Way Galaxy by surveying more than a thousand million stars.  Gaia will monitor each of its target stars about 70 times over a five-year period.


---------------------  3612  -  GAIA  Space Telescope  -  data is pouring in?

-  Gaia will precisely chart star positions, distances, movements, and changes in brightness. It is expected to discover hundreds of thousands of new celestial objects, such as extra-solar planets and brown dwarfs, and observe hundreds of thousands of asteroids within our own Solar System. 

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-  The mission will also study about 500,000 distant quasars and will provide stringent new tests of Albert Einstein’s General Theory of Relativity.  It will create an extraordinarily precise three-dimensional map of more than a thousand million stars throughout our Galaxy and beyond, mapping their motions, luminosity, temperature and composition. 

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-  This huge stellar census will provide the data needed to tackle an enormous range of important problems related to the origin, structure and evolutionary history of our Galaxy. Gaia will identify which stars are relics from smaller galaxies long ago ‘swallowed’ by the Milky Way.

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-    By watching for the large-scale motion of stars in our Galaxy, it will also probe the distribution of dark matter, the invisible substance thought to hold our Galaxy together.

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-  Gaia will achieve its goals by repeatedly measuring the positions of all objects down to magnitude 20 which is about 400,000 times fainter than can be seen with the naked eye.

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-  For all objects brighter than magnitude 15 (4,000 times fainter than the naked eye limit), Gaia will measure their positions to an accuracy of 24 micro-arcseconds. This is comparable to measuring the diameter of a human hair at a distance of 1,000 kilometers.

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-  It will allow the nearest stars to have their distances measured to the extraordinary accuracy of 0.001%. Even stars near the Galactic center, some 30,000 light-years away, will have their distances measured to within an accuracy of 20%.

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-  Gaia contains two optical telescopes that work with three science instruments to precisely determine the location of stars and their velocities, and to split their light into a spectrum for analysis.

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-  During its five-year mission, the spacecraft spins slowly, sweeping the two telescopes across the entire celestial sphere. As the detectors repeatedly measure the position of each celestial object, they will detect any changes in the object’s motion through space.

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-  After launch, Gaia unfolded a ‘skirt’ just over 10 meters in diameter. This acts as both a sunshade to permanently shade the telescopes and allow their temperatures to drop to below –100°C, and as a power generator for the spacecraft. The underside of the shield is partially covered with solar panels and will always be facing the Sun, generating electricity to operate the spacecraft and its instruments.

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-  Gaia is mapping the stars from an orbit around the Sun, at a distance of 1.5 million km beyond Earth’s orbit. This special location, known as the L2 Lagrangian point, keeps pace with Earth as we orbit the Sun. It offers a clearer view of the cosmos than an orbit around Earth, which would result in the spacecraft passing in and out of Earth's shadow and causing it to heat up and cool down, distorting its view. Free from this restriction and far away from the heat radiated by Earth, L2 provides a much more stable viewpoint.

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-  Gaia has its roots in ESA’s Hipparcos mission (1989-1993), which catalogued more than 100,000 stars to high precision, and more than a million to lesser precision. Now, some 20 years later, Gaia will catalogue a thousand million stars, measuring each star's position and motion 200 times more accurately than Hipparcos, and producing 10,000 times more data than its predecessor.

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-  Gaia's massive third data release is out, June, 2022.  This data release called (DR3) by the ESA’s Gaia Observatory.  DR3 contains new and improved details for almost two billion stars in our galaxy, including the chemical compositions, temperatures, colors, masses, ages, and the velocities at which stars move. 

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-   Much of this information consists of newly released spectroscopy data, a technique in which starlight is split into the color spectrum and analyzed to determine how it is being shifted. This technique is known as “radial velocity” ( Doppler Spectroscopy), where light is shifted towards the red or blue end of the spectrum ( redshift and blueshift) based on whether the object is moving towards or away from Earth (respectively). Astrophysicists use this technique to determine how a star is moving relative to our own and also for the sake of detecting exoplanets.

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-  This latest release also includes data on special subsets of stars, like those that undergo changes in brightness over time ( variable stars). The DR3 also contained the largest catalog of binary star systems, thousands of Solar System objects (asteroids and moons), and millions of galaxies and quasars outside the Solar System (like Andromeda). Other major discoveries include the ability of Gaia to detect tiny motions on the surface of a star (Starquakes) and improved data on the chemical compositions of stars.

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-  Starquakes are a phenomenon where the crust of a star undergoes a sudden adjustment that changes its shape. This was a surprise to astronomers since it is not something the observatory was not originally built for. Previously, Gaia data pointed towards radial oscillations that cause stars to swell and shrink periodically but leave their shape unaffected. The latest data demonstrates that Gaia can also detect nonradial oscillations that are far more powerful but harder to detect because they change the star’s shape globally.

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-  Gaia detected strong nonradial starquakes on the surface of thousands of stars, even where conventional theory states that none should exist. Much like how Earthquakes and similar phenomena on other bodies allow astronomers to learn more about the interior of planets and moons, these starquakes can tell astronomers a great deal about the internal workings of different star types.

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-  By studying the chemical composition of stars, astronomers can place tighter constraints on where the stars were born and how they migrated over time. This, in turn, can reveal interesting details about the history of the Milky Way and how it has evolved since. 

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-  With the DR3, Gaia has revealed the largest chemical map of the galaxy from our solar system to smaller galaxies surrounding the Milky Way. Coupled with proper motion and velocity measurements (astrometry) in the catalog, this information has provided a 3D map of where stars originated and got to where they are today.

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-  The key aspect of stellar composition is the amount of heavy metals they contain, “metallicity.” The first stars in the Universe, which formed roughly 100 million years after the Big Bang, were composed of hydrogen and helium, reflecting the composition of the Universe at the time. 

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-  These Population III stars  formed heavier elements in their interiors through a slow process of nuclear fusion, where fusion and helium were merged to create boron, carbon, nitrogen, oxygen, silicon, and eventually iron.

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-  When these stars collapsed at the end of their life cycles and exploded in massive supernovae, these elements were dispersed through the interstellar medium from which new stars formed. This active cycle of star formation and death slowly enriched the interstellar medium with metals over time. 

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-  Subsequent generations of stars, known as Population II and I, contained greater and greater amounts of these elements, which can be used to determine their age. In this respect, a star’s chemical composition is like its DNA.

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-  Gaia has revealed that some stars in our galaxy are “metal-poor” and composed of primordial material, while others like our Sun are rich in metal. The data also showed that stars closer to the center and plane of our galaxy have higher metallicities than those farther from the center and outside the galactic disk.

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-    Based on their compositions, Gaia also identified numerous stars that formed in different galaxies but were captured by the Milky Way or became part of it through galactic mergers.

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-   This diversity is extremely important, because it tells us the story of our galaxy’s formation. It reveals the processes of migration within our galaxy and accretion from external galaxies. It also clearly shows that our Sun, and we, all belong to an ever changing system, formed thanks to the assembly of stars and gas of different origins.

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-  The new binary star catalog contains data on the mass and evolution of more than 800,000 binary systems. 

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-  Another breakthrough is a new asteroid survey that provides data on the origins of 156,000 thousand rocky bodies in our Solar System.

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-   Gaia‘s observations have revealed about 10 million variable stars, macro-molecules in the medium, and quasars and galaxies.  While surveying the entire sky with billions of stars multiple times, Gaia is bound to make discoveries that other more dedicated missions would miss. 

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-  The mission has been approved until the end of 2022, and there are indications that it will be extended further to 2025.  This final product will contain the most precise astronomical measurements ever made and will include:

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-----------------------  Full astrometric, photometric, and radial-velocity catalogs

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-----------------------  All available variable-star and non-single-star solutions

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-----------------------  Source classifications (probabilities) plus multiple astrophysical parameters for stars, unresolved binaries, galaxies, and quasars.

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-----------------------  An exo-planet list

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-----------------------  All epoch and transit data for all sources

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-   This data should keep astronomers busy for along time.  Many more astronomical papers to be published.  More JimsAstronomy Reviews to follow:

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June 25, 2022      GAIA  Space Telescope  -  data is pouring in?              3612                                                                                                                                           

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--------------------- ---  Saturday, June 25, 2022  ---------------------------






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