When we compare the mass in C/LINEAR before the breakup to the mass of debris observed after the breakup, there seems to be a problem: we come up short in the mass of the debris by almost a factor of 100. Here are the numbers. In their recently published article in the journal Science, Farnham et al. estimate that the diameter of the original nucleus was about 880 meters (1/2 mile). If we assume that the density of the nucleus was about 0.5 g/cm^3 (i.e., about 1/2 that of water), the estimated mass of the nucleus is about 200 billion kilograms (about 200 million tons). Weaver et al., in their Science paper, estimated the mass of the largest remaining fragments after the breakup to be about 3 billion kilograms (3 million tons). They also estimated that the mass in the dust tail was only about 0.3 billion kilograms (0.3 million tons). The largest fragments and the tiny dust were the only portions of the breakup debris that could be seen directly in telescopes, and their sum falls far short of the mass of the original nucleus. Where is the rest? By studying several images of the dust tail, Farnham et al. found that the size distribution of the dust was much more heavily weighted towards larger particles than is normally observed in comets. This might be expected because C/LINEAR broke apart and was able to release all of its dust, whereas most comets cannot push their largest particles off the surface of the nucleus. Farnham's analysis only directly applies to dust that's smaller than about 300 micrometers (0.1 inches), but if the slope of the observed size distribution continued all the way out to objects as large as 10 meters, then there is more than enough material in these ``unseen'' objects to account for the missing mass. The big question is how far out does the slope continue to stay relatively flat? We know that the slope must dramatically fall by the time we get to 50 meter sized objects; otherwise the HST and VLT would have seen tens of thousands of large fragments instead of 15 to 20. But it seems reasonable to expect that the slope hangs in there, or at least doesn't drop off too much, for objects in the meter size range. If so, then the missing mass problem is resolved. The only other way to resolve this problem is to conclude that the size of the original nucleus was overestimated by Farnham et al. by about a factor of 3 to 4, which would bring the diameter of the original nucleus down to about 250 meters. We've never seen a cometary nucleus this small before, and C/LINEAR seems to have been producing too much gas to have been this small.

Go to the top of this webpage Back to the main C/LINEAR page. Direct questions to: Hal Weaver Last updated: 18 May 2001