Science

    		  

    Gaia's key objective is a detailed study of the Milky Way that will reveal our Galaxy's content, dynamics, current state and formation history. By surveying celestial bodies down to the very faint magnitude 20, Gaia takes in a representative fraction of the Milky Way's population, providing data to tackle unanswered questions about our home galaxy. The all-sky survey of about one billion stars also provides unique insight into many other areas of astronomy.

    The scientific measurements of the Gaia mission cover three principal areas: astrometry (the measurement of stellar position, parallax, and proper motion), photometry (the measurement of photometric magnitudes in a number of different spectral bands and at each possible measurement epoch) and spectroscopy (for the acquisition of radial velocities and astrophysical parameters).

    For more information about Gaia's Science, visit the Science Objectives, Science Topics - Information Sheets and Science Performance sections.

     

     

    Key Facts

    		  
    Science Objectives:  
    • Galaxy origin and formation
    • Physics of stars and their evolution
    • Galactic structure and dynamics
    • Distance scale and reference frame
    • Solar-system census
    • Detection of all classes of astrophysical objects including brown dwarfs, white dwarfs, and planetary systems
    • Variable stars
    • Double and multiple stars
    • Fundamental physics
    		  
    Science Topics and Goals:  

    The Galaxy:

    • origin and history of our Galaxy
    • tests of hierarchical structure formation theories
    • star formation history
    • chemical evolution
    • inner bulge/bar dynamics
    • disk/halo interactions
    • dynamical evolution
    • nature of the warp
    • star cluster disruption
    • dynamics of spiral structure
    • distribution of dust
    • distribution of invisible mass
    • detection of tidally disrupted debris
    • Galaxy rotation curve
    • disk mass profile

    Star formation and evolution:

    • in situ luminosity function
    • dynamics of star forming regions
    • luminosity function for pre-main sequence stars
    • detection and categorization of rapid evolutionary phases
    • complete and detailed local census down to single brown dwarfs
    • identification/dating of oldest halo white dwarfs
    • age census
    • census of binaries and multiple stars

    Local Group and beyond:

    • rotational parallaxes for Local Group galaxies
    • kinematical separation of stellar populations
    • galaxy orbits and cosmological history
    • zero proper motion quasar survey
    • cosmological acceleration of Solar System
    • photometry of galaxies
    • detection of supernovae

    Distance scale and reference frame:

    • parallax calibration of all distance scale indicators
    • absolute luminosities of Cepheids
    • distance to the Magellanic Clouds
    • definition of the local, kinematically non-rotating metric

    Extra-solar planetary systems:

    • complete census of large planets to 200–500 pc
    • orbital characteristics of several thousand systems

    Solar System:

    • deep and uniform detection of minor planets
    • taxonomy and evolution
    • inner Trojans
    • Kuiper Belt Objects
    • disruption of Oort Cloud

    Specific objects:

    • 106 − 107 resolved galaxies; 20 000 extragalactic supernovae; 500 000 quasars; 250 000 solar system objects; 500 brown dwarfs; 15 000 extra-solar planets; 200 000 disk white dwarfs; 100 astrometric and 1000 photometric microlensed events; 107 resolved binaries within 250 pc

     

    Fundamental physics:

    • PPN γ to ~2 × 10−6; PPN β to 3 × 10−4 − 3 × 10−5; solar J2  to 10−7 − 10−8; Ġ / G to 10−12 − 10−13 yr−1; constraints on gravitational wave energy for 10−12 < f < 4 × 10−9 Hz; constraints on ΩM  and ΩΛ  from quasar microlensing


    Science Performance:  

    Catalogue:

    • ~1 billion stars; 0.77×106 to G = 10 mag; 47×106 to G = 15 mag; 360×106 to G = 18 mag; 1192 × 106 to G = 20 mag; completeness to about G = 20 mag

    Sky density:

    • mean density ~25 000 stars deg−2; maximum density ~750,000 stars deg−2

    Accuracies:

    • median parallax errors: 7 µas at G = 10 mag; 26 µas at G = 15 mag; 600 µas at G = 20 mag

    Radial velocity accuracies:

    • 1–15 km s−1 to GRVS ≈ 16 mag, depending on spectral type

    Tangential velocity accuracies:

    • from Galaxy models: 5 million better than 0.5 km s−1; 10 million better than 1 km s−1; 25 million better than 3 km s−1; 40 million better than 5 km s−1; 60 million better than 10 km s−1

    Distance accuracies:

    • from Galaxy model: 10 million better than 1 percent; 20 million better than 2 percent; 50 million better than 5 percent; 100 million better than 10 percent

    Photometry:

    • to G = 20 mag in broadband light, and spectrally-dispersed light, with some 20 independent spectral samples between 330–1050 nm