We present here the analysis of about 19,500 new star hours of low ecliptic latitude observations ( |b| \leq 20 ^ { \circ } ) obtained by the Hubble Space Telescope ’ s Fine Guidance Sensors over a time span of more than nine years ; which is an addition to the \sim 12 , 000 star hours previously analyzed by Schlichting et al .
( 34 ) .
Our search for stellar occultations by small Kuiper belt objects ( KBOs ) yielded one new candidate event corresponding to a body with a 530 \pm { 70 } m radius at a distance of about 40 AU .
Using bootstrap simulations , we estimate a probability of \approx 5 \% , that this event is due to random statistical fluctuations within the new data set .
Combining this new event with the single KBO occultation reported by Schlichting et al .
( 34 ) we arrive at the following results : 1 ) The ecliptic latitudes of 6.6 ^ { \circ } and 14.4 ^ { \circ } of the two events are consistent with the observed inclination distribution of larger , 100 km-sized KBOs .
2 ) Assuming that small , sub-km sized KBOs have the same ecliptic latitude distribution as their larger counterparts , we find an ecliptic surface density of KBOs with radii larger than 250 m of N ( r > 250 m ) = 1.1 ^ { +1.5 } _ { -0.7 } \times 10 ^ { 7 } { deg ^ { -2 } } ; if sub-km sized KBOs have instead a uniform ecliptic latitude distribution for -20 ^ { \circ } < b < 20 ^ { \circ } then N ( r > 250 m ) = 4.4 ^ { +5.8 } _ { -2.8 } \times 10 ^ { 6 } { deg ^ { -2 } } .
This is the best measurement of the surface density of sub-km sized KBOs to date .
3 ) Assuming the KBO size distribution can be well described by a single power law given by N ( > r ) \propto r ^ { 1 - q } , where N ( > r ) is the number of KBOs with radii greater than r , and q is the power law index , we find q = 3.8 \pm { 0.2 } and q = 3.6 \pm { 0.2 } for a KBO ecliptic latitude distribution that follows the observed distribution for larger , 100-km sized KBOs and a uniform KBO ecliptic latitude distribution for -20 ^ { \circ } < b < 20 ^ { \circ } , respectively .
4 ) Regardless of the exact power law , our results suggest that small KBOs are numerous enough to satisfy the required supply rate for the Jupiter family comets .
5 ) We can rule out a single power law below the break with q > 4.0 at 2 \sigma , confirming a strong deficit of sub-km sized KBOs compared to a population extrapolated from objects with r > 45 ~ { } km .
This suggests that small KBOs are undergoing collisional erosion and that the Kuiper belt is a true analogue to the dust producing debris disks observed around other stars .