We present the discovery of three new Milky Way satellites from our search for compact stellar overdensities in the photometric catalog of the Panoramic Survey Telescope and Rapid Response System 1 ( Pan-STARRS 1 , or PS1 ) 3 \pi survey .
The first satellite , Laevens 3 , is located at a heliocentric distance of d = 67 \pm 3 { kpc } .
With a total magnitude of M _ { V } = -4.4 \pm 0.3 and a half-light radius r _ { h } = 7 \pm 2 { pc } , its properties resemble those of outer halo globular clusters .
The second system , Draco II/Laevens 4 ( Dra II ) , is a closer and fainter satellite ( d \sim 20 { kpc } , M _ { V } = -2.9 \pm 0.8 ) , whose uncertain size ( r _ { h } = 19 ^ { +8 } _ { -6 } { pc } ) renders its classification difficult without kinematic information ; it could either be a faint and extended globular cluster or a faint and compact dwarf galaxy .
The third satellite , Sagittarius II/Laevens 5 ( Sgr II ) , has an ambiguous nature as it is either the most compact dwarf galaxy or the most extended globular cluster in its luminosity range ( r _ { h } = 37 ^ { +9 } _ { -8 } { pc } and M _ { V } = -5.2 \pm 0.4 ) .
At a heliocentric distance of 67 \pm 5 { kpc } , this satellite lies intriguingly close to the expected location of the trailing arm of the Sagittarius stellar stream behind the Sagittarius dwarf spheroidal galaxy ( Sgr dSph ) .
If confirmed through spectroscopic follow up , this connection would locate this part of the trailing arm of the Sagittarius stellar stream that has so far gone undetected .
It would further suggest that Sgr II was brought into the Milky Way halo as a satellite of the Sgr dSph .