Limits on the Flux of Nuclearites and Other Heavy Compact Objects from the Pi of the Sky Project

Many theories predict the existence of very heavy compact objects, that in terms of sizes would belong to the realms of nuclear or atomic physics, but in terms of masses could extend to the macroscopic world, reaching kilograms, tonnes, or more. If they exist, it is likely that they reach our planet with high speeds and cross the atmosphere. Because of their high mass-to-size ratio and huge energy, in many cases, they would leave behind a trail in the form of sound and seismic waves, etches, or light in transparent media. Here we show results of a search for such objects in visual photographs of the sky taken by the “Pi of the Sky” experiment, illustrated with the most stringent limits on the isotropic flux of incoming so-called nuclearites, spanning between $5.4\times {10}^{-20}$ and $2.2\times {10}^{-21}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}{\mathrm{sr}}^{-1}$ for masses between 100 g and 100 kg. In addition we establish a directional flux limit under an assumption of a static “sea” of nuclearites in the Galaxy, which spans between $1.5\times {10}^{-18}$ and $2.1\times {10}^{-19}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ in the same mass range. The general nature of the limits presented should allow one to constrain many specific models predicting the existence of heavy compact objects and both particle physics and astrophysical processes leading to their creation, and their sources.

Figure 1

The longest of the remaining nuclearite candidates. Left: the track on the frame after subtraction of the previous frame and Gaussian smoothing. Right: the intensity profile of the event, with the curve showing the Gaussian smoothing of the measurement points.

Figure 2

90% C.L. limit for the isotropic flux of nuclearites of specific mass by the Pi of the Sky project on top of the limits given by MACRO and a mica minerals analysis. We show also the constraint in the SHM dark matter scenario, assuming its isotropic flux on Earth.

Figure 3

90% C.L. limit for the directional flux of nuclearites of specific mass by the Pi of the Sky project.