New 21cm H I observations made with the Green Bank Telescope show that the high-velocity cloud known as Smith ’ s Cloud has a striking cometary appearance and many indications of interaction with the Galactic ISM .
The velocities of interaction give a kinematic distance of 12.4 \pm 1.3 kpc , consistent with the distance derived from other methods .
The Cloud is > 3 \times 1 kpc in size and its tip at ( \ell,b ) \approx 39 \arcdeg - 13 \arcdeg is 7.6 kpc from the Galactic center and 2.9 kpc below the Galactic plane .
It has > 10 ^ { 6 } M _ { \sun } in H I .
Its leading section has a total space velocity near 300 km s ^ { -1 } , is moving toward the Galactic plane with a velocity of 73 \pm 26 km s ^ { -1 } , and is shedding material to the Galaxy .
In the absence of drag the Cloud will cross the plane in about 27 Myr .
Smith ’ s Cloud may be an example of the accretion of gas by the Milky Way needed to explain certain persistant anomalies in Galactic chemical evolution .