Date of Award


Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Physics (PhD)

Administrative Home Department

Department of Physics

Advisor 1

Robert J. Nemiroff

Committee Member 1

Petra Huentemeyer

Committee Member 2

Yang Yang

Committee Member 3

Bijunath R. Patla


Location, orbit and energy of a meteoroid impacting the moon during the Lunar Eclipse of January 21, 2019

During the total lunar eclipse of January 21, 2019 at least two meteoroids impacted the moon producing visible flash lights on the near side. One of the impacts occurred on the darkest side of the visible lunar face and was witnessed by many astrophotographers. In this paper we present estimations of the location, impact parameters (velocity and incoming direction), orbit and energy of the meteoroid, as obtained from images and videos collected by amateur astronomers in Colombia, the Dominican Republic, Morocco, USA, Canary Islands, Cape Verde, Czech Republic, Austria, and Germany. Astrometric measurements on the images put the impact location at selenographic lat = -29.43 and lon = -67.89 while photometric measurements predict the flash brightness of Gf = 6.7. The novel Gravitational Ray Tracing (GRT) technique is used to estimate the orbital properties and radiant of the impactor. We find that that the meteoroid impacted the moon with a speed of 13.8 km/s (70% C.L.) and in a relatively shallow angle, (6 of visible light in a short time (0.3 seconds). The total impact energy was ~0.5 tons of TNT which correspond to a body with a mass ~20 kg and a diameter of ~30 cm. If our assumptions are correct, the crater left by the impact will have ~10 meters across and it could be detectable by prospecting lunar probes. These results arose from a timely collaboration between professional and amateur astronomers which highlight the importance of citizen science in contemporary astronomy.

Testing the Weak Equivalence Principle with Cosmological Gamma Ray Bursts

Gamma Ray Bursts (GRBs) with rapid variations at cosmological distances are used to place new limits on violations of the gravitational weak equivalence principle (WEP). These limits track intrinsic timing deviations between GRB photons of different energies as they cross the universe, in particular in the KeV to GeV energy range. Previous limits in this energy range have involved only the gravitational potential of local sources and utilized temporal variability on the order of 0.1 seconds. Here WEP violation limits are derived from sources with greater distance, faster variability, and larger intervening mass. Specifically, GRB sources with redshifts as high as 6.5 are considered, with variability as fast 0.2 milliseconds, and passing the gravitational potentials of inferred clusters of galaxies distributed randomly around the line of sight. WEP violation limits are derived from data from GRB 910711, GRB 920229, GRB 021206, GRB 051221, GRB 090429, and GRB 090510. The strongest constraint in the very early universe comes from GRB 090429 which limits gamma (500 keV) - gamma(250 keV) < 1.2 x 10-13. The strongest overall constraint comes from GRB 090510 which yields a WEP violation limit of gamma(30 GeV) - gamma (1 GeV) < 6.6 x 10-16. This strongest constraint is not only a new record for WEP violation limit for gamma-ray photons and in the early universe, but the strongest upper bound for Delta gamma that has ever been recorded between any two energy bands.

Available for download on Thursday, April 16, 2020