Ο πρώτος 3D χάρτης του Γαλαξία. Billion-star map of Milky Way set to transform astronomy

Η αποστολή GAIA χαρτογράφησε 1,7 δισ. άστρα του γαλαξία μας. European Gaia spacecraft’s first major data dump — the most detailed 3D chart yet of our Galaxy — will keep researchers busy for decades. The Milky Way galaxy has been charted by the Gaia mission in unprecedented detail. Credit: ESA/Gaia/DPAC

Ο Ευρωπαϊκός Οργανισμός Διαστήματος (ESA) έδωσε στην δημοσιότητα ένα τρισδιάστατο χάρτη του γαλαξία μας στον οποίο είναι σημειωμένα στις θέσεις στις οποίες βρίσκονται 1,7 δισ. άστρα. Ο χάρτης αυτός είναι προϊόν της λειτουργίας του διαστημικού παρατηρητηρίου GAIA που εκτοξεύτηκε πριν από πέντε έτη.

Gaia’s all-sky view of our Milky Way Galaxy and neighbouring galaxies, based on measurements of nearly 1.7 billion stars. The map shows the total brightness and colour of stars observed by the ESA satellite in each portion of the sky between July 2014 and May 2016. Brighter regions indicate denser concentrations of especially bright stars, while darker regions correspond to patches of the sky where fewer bright stars are observed. The colour representation is obtained by combining the total amount of light with the amount of blue and red light recorded by Gaia in each patch of the sky.  The bright horizontal structure that dominates the image is the Galactic plane, the flattened disc that hosts most of the stars in our home Galaxy. In the middle of the image, the Galactic centre appears vivid and teeming with stars. Darker regions across the Galactic plane correspond to foreground clouds of interstellar gas and dust, which absorb the light of stars located further away, behind the clouds. Many of these conceal stellar nurseries where new generations of stars are being born. Sprinkled across the image are also many globular and open clusters – groupings of stars held together by their mutual gravity, as well as entire galaxies beyond our own.  The two bright objects in the lower right of the image are the Large and Small Magellanic Clouds, two dwarf galaxies orbiting the Milky Way.  In small areas of the image where no colour information was available – to the lower left of the Galactic centre, to the upper left of the Small Magellanic Cloud, and in the top portion of the map – an equivalent greyscale value was assigned. The second Gaia data release was made public on 25 April 2018 and includes the position and brightness of almost 1.7 billion stars, and the parallax, proper motion and colour of more than 1.3 billion stars. It also includes the radial velocity of more than seven million stars, the surface temperature of more than 100 million stars, and the amount of dust intervening between us and of 87 million stars. There are also more than 500 000 variable sources, and the position of 14 099 known Solar System objects – most of them asteroids – included in the release.  Credit: Gaia Data Processing and Analysis Consortium (DPAC); A. Moitinho / A. F. Silva / M. Barros / C. Barata, University of Lisbon, Portugal; H. Savietto, Fork Research, Portugal.

Το Global astrometric interferometer for astrophysics (Παγκόσμιο Αστρομετρικό Συμβολόμετρο για την Αστροφυσική) είχε την ικανότητα να μετράει με πολύ μεγάλη ακρίβεια τις θέσεις και τις αποστάσεις ενός εκατομμυρίου αστέρων την ημέρα. Για τα περίπου 1,3 δισ. άστρα του χάρτη εκτός από το σημείο στο οποίο βρίσκονται υπάρχουν και πληροφορίες για την τροχιακή τους κίνηση, την ταχύτητα με την οποία κινούνται, την απόχρωση που έχουν κ.α.

Gaia's all-sky view of our Milky Way Galaxy and neighbouring galaxies. The maps show the total brightness and colour of stars (top), the total density of stars (middle) and the interstellar dust that fills the Galaxy (bottom). These images are based on observations performed by the ESA satellite in each portion of the sky between July 2014 and May 2016, which were published as part of Gaia's second data release on 25 April 2018. Credit: ESA/Gaia/DPAC

Πρόκειται στην πραγματικότητα για ένα πραγματικό ωκεανό αστρονομικών δεδομένων στον οποία η παγκόσμια επιστημονική κοινότητα αδημονεί να… βουτήξει. Η ESA ανακοίνωσε ότι λίγες μόλις ώρες μετά την δημοσιοποίηση του χάρτη περισσότερα από τρεις χιλιάδες άτομα «κατέβασαν» τον χάρτη και τα δεδομένα στους υπολογιστές τους.

Animated view of the 14 099 asteroids in our Solar System, as viewed by ESA’s Gaia satellite using information from the mission’s second data release. The orbits of the 200 brightest asteroids are also shown, as determined using Gaia data. In future data releases, Gaia will also provide asteroid spectra and enable a complete characterisation of the asteroid belt. The combination of dynamical and physical information that is being collected by Gaia provides an unprecedented opportunity to improve our understanding of the origin and the evolution of the Solar System. Credit: ESA/Gaia/DPAC

«Είμαστε πραγματικά πολύ περίεργοι να δούμε πώς θα αξιοποιήσει η επιστημονική κοινότητα αυτό το υλικό» δηλώνει ο Αντονι Μπράουν, του Πανεπιστημίου Leiden στην Ολλανδία που είναι επικεφαλής της ομάδας επεξεργασίας των δεδομένων της αποστολής GAIA το κόστος της οποίας άγγιξε το 1 δισ. ευρώ.

Πηγές: Gerard Gilmore. Gaia: 3-dimensional census of the Milky Way Galaxy, Contemporary Physics (2018). DOI: 10.1080/00107514.2018.1439700 - http://sci.esa.int/gaia/60192-gaia-creates-richest-star-map-of-our-galaxy-and-beyond/ - https://www.nature.com/articles/d41586-018-04979-4 - http://www.tovima.gr/science/physics-space/article/?aid=970585