Summary of the GAIA Science Capabilities

Objectives: Galaxy origin and formation; physics of stars and their evolution; Galactic dynamics and distance scale; solar system census; large-scale detection of all classes of astrophysical objects including brown dwarfs, white dwarfs, and planetary systems; fundamental physics

Measurement Capabilities

catalogue: of the order of 1 billion stars; 0.34×10⁶ to V=10 mag; 26×10⁶ to V=15 mag; 250×10⁶ to V=18 mag; 1000×10⁶ to V=20 mag, completeness to about 20 mag
sky density: mean density approximately 25,000 stars deg^-2, maximum density: about 3 ×10⁶ stars deg^-2
accuracies: median parallaxes of 4 µas at V=10 mag, 11 µas at V=15 mag, 160 µas at V=20 mag

GAIA capabilities versus other astrometric space missions

distance accuracies: from Galaxy models: 21 million better than 1 per cent, 46 million better than 2 per cent, 116 million better than 5 per cent, 220 million better than 10 per cent,
radial velocities: 1 to 10 km s^-1 to V=16-17 mag
photometry: to V = 20 mag in 4 broad and 11 medium bands

Summary Scientific Goals

Galactic structure: origin and history of our Galaxy --- tests of hierarchical structure formation theories --- inner bulge/bar dynamics --- disk/halo interactions --- dynamical evolution --- nature of the warp --- star cluster disruption --- dynamics of spiral structure --- star formation history --- chemical evolution --- distribution of dust --- distribution of invisible mass --- detection of tidally disrupted debris --- Galaxy rotation curve --- disk mass profile
star formation and evolution: 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 brown dwarfs in binaries
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
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
solar system: deep and uniform detection of minor planets --- taxonomy and evolution --- disruption of Oort Cloud
extra-solar planetary systems: complete census of large planets to 200--500 pc --- orbital characteristics of several thousand systems
fundamental physics: space curvature parameter, gamma, to 5×10^-7; constraints on beta, on the rate of change of the gravitational constant, and gravitational wave energy
specific objects: 10⁶ galaxies; 10⁵ supernovae; 10⁵-10⁶ (new) solar system objects; more than 50,000 brown dwarfs; 30,000 extra-solar planets; 200,000 disk white dwarfs; approximately 1000 microlensed events; TBC resolved binaries

Summary of the capabilities of space astrometry missions

Mission	Agency	Launch	Number of stars	Magnitude limit	Accuracy
					mas	mag
Hipparcos	ESA	1989	120000	12	1	10
DIVA	Germany	2003	30 million	15	0.2	8
"	"	"	"	"	5	15
FAME(*)	USNO/NASA	2004	40 million	15	0.015	9
"	"	"	"	"	0.220	15
SIM(*)	NASA	2005	>20000	20	0.003	20
GAIA	ESA	prior to 2012	>1 billion	20	0.003	12
"	"	"	"	"	0.010	15
"	"	"	"	"	0.200	20
(*) approved by NASA

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Updated on: October 16, 2000