Western Kentucky University TopSCHOLAR® Masters Theses & Specialist Projects Graduate School Summer 2018 Characterization of Eight Potentially Hazardous Near Earth Asteroids: Rotation Period Analysis and Structure Modeling Via Light Curve Inversion Techniques Stacy Jo Hicks Western Kentucky University, [email protected] Follow this and additional works at: https://digitalcommons.wku.edu/theses Part of the Physics Commons, and the The unS and the Solar System Commons Recommended Citation Hicks, Stacy Jo, "Characterization of Eight Potentially Hazardous Near Earth Asteroids: Rotation Period Analysis and Structure Modeling Via Light Curve Inversion Techniques" (2018). Masters Theses & Specialist Projects. Paper 3060. https://digitalcommons.wku.edu/theses/3060 This Thesis is brought to you for free and open access by TopSCHOLAR®. It has been accepted for inclusion in Masters Theses & Specialist Projects by an authorized administrator of TopSCHOLAR®. For more information, please contact [email protected]. CHARACTERIZATION OF EIGHT POTENTIALLY HAZARDOUS NEAR EARTH ASTEROIDS: ROTATION PERIOD ANALYSIS AND STRUCTURE MODELING VIA LIGHT CURVE INVERSION TECHNIQUES A Thesis Presented to The Faculty of the Department of Physics and Astronomy Western Kentucky University Bowling Green, KY In Partial Fulfillment Of the Requirement for the Degree Master of Science By Stacy Hicks August 2018 ACKNOWLEDGEMENTS I would like to thank my mentor, Dr. Michael Carini, for his guidance and support throughout my undergraduate and graduate career at Western Kentucky University. I would also like to thank the members of my committee, Dr. Ivan Novikov, Dr. Steven Gibson, and Dr. Michael Carini, for their advice and guidance. A special thank you Ms. Sharon Windham for her administrative support and “therapy” sessions; and Dr. Douglas Harper for help with programming and for allowing me to sit in on his classes to acquire the knowledge I needed to complete this thesis. A special thank you to Carl Hergenrother and Delores Hill, NASA OSIRIS-REx Target Asteroids Leads, for providing me the opportunity to be part of the OSIRIS-REx mission and allowing access to Target Asteroids data, and for their guidance along the way. Thank you to Dr. Patrick Miller of the International Astronomical Search Collaboration. I would also like to thank NASA/Kentucky Graduate Fellowship for funding this project. A special thank you to my friends and family for their love and support without which I could not have made it through this journey. I would also like to thank the entire WKU Department of Physics and Astronomy for making WKU feel like home. III CONTENTS Chapter 1: Introduction…………….....………………………………………...………....1 Background………………………………………………………………..………1 Detection & Classification of NEAs and PHAs………………..…..……….…….5 Scope of Project……………………………………………..……………….……8 Asteroid Characteristics & Characterization…………………………….…….....10 Rotation Period & Structural Classification………………….…………….…….13 Impact Mitigation & Risk Classification…………….....…….……………..……14 Targets Background………………………………………………..…………….17 Phaethon………………………………………………………………….17 Icarus……………………………………………………………………..18 Hathor………………………………………..…………………………..19 Bede……………………………………………………...………………20 2004 JN 13……………………………………………………………….20 2002 FG 7…………………………………………….…………………..21 2004 QQ………………………………………………………………….21 2004 BL 86……………………………………………………………….21 Chapter 2: Data & Methods……………………......…………………………………….23 IV RCT Observations…………………………………………….……….…………23 Target Asteroids Observations……………………………………...……………23 ALCDEF Photometry Database………………………………………………….23 Data Processing……………………………………….………………………….24 Chaper 3: Analysis Techniques………………………………………………………….27 Lomb-Scargle Time Series Analysis………………………………….………….27 Light Curve Inversion Techniques………………………………….……………29 Convex Inversion…………………………………………………...……29 Determination of Pole & Rotation Period………………………………...32 Treatment of Data…………………………………………….…………………..32 Chaper 4: Period Determination & Structure Modeling………………………………….33 Phaethon………………………………………………………………………….34 Icarus……………………………………………………………………………..36 Hathor……………………………………………………..……………………..37 Bede……………………………………………………………………………39 2004 JN 13……………………………………………………….…………….42 2002 FG 7……………………………………………………….……………..44 2004 QQ……………………………………………………………………….45 V 2004 BL 86…………………………………………………………………….46 Structure Modeling…………………………………….………………………48 2002 FG7………………………………………………………………49 2004 JN13……………………………….…………………………….50 Icarus…………………………………….….…………………………51 Chapter 5: Conclusions…………………………………..……………………………53 Future Work…………………………………………..………….……………56 References……………………………………………………………………………..57 Appendix: Abbreviations & Symbols……………………...…………………………..65 VI List of Tables Table 1: Number of known asteroids per orbit classification............................................11 Table 2: Summary of observations via source……………………….………………….24 Table 3: Summary of data per target for structure modeling…………………………….31 Table 4: Summary of data used in light curve inversion modeling…………………..….49 Table 5: Rotation period results summary ………………………………………………54 Table 6: Inversion structure modeling results summary………………………………....54 VII CHARACTERIZATION OF EIGHT POTENTIALLY HAZARDOUS NEAR EARTH ASTEROIDS: ROTATION PERIOD ANALYSIS AND STRUCTURE MODELING VIA LIGHT CURVE INVERSION TECHNIQUES Stacy Hicks August 2018 66 Pages Directed by: Michael Carini, Steven Gibson, and Ivan Novikov Department of Physics and Astronomy Western Kentucky University The term “homeland security”, seems to have become synonymous with terrorism in the minds of the general public. However, there are other threats to the security of the United States homeland that can be just as, if not more, devastating than terrorism. Included among these other threats is the potential of an asteroid collision with Earth. Historically, asteroid impact events have been responsible for the devastation of our planet and many of the mass extinction events encountered throughout the geologic record. Knowledge of physical parameters such as structure and rotational dynamics of the asteroid are critical parameters in developing interception and deflection techniques, as well as assessing the risk associated with these bodies and mitigation planning in the event of impact. This thesis encompasses the study of eight potentially hazardous asteroids identified in conjunction with NASA’s OSIRIS REX Mission and observed via the Target Asteroid Project, along with observations from the Robotically Controlled Telescope, and the Asteroid Light Curve Database of Photometry. Photometric data was extracted from all observations. Rotation periods of each target were confirmed using Lomb-Scargle time series analysis, with possible secondary periods indicated in the cases of Hathor (2.2169 hours), Bede (161.1501 hours), and Phaethon (4.5563 hours). Shape models for 2002 FG7, 2004 JN13, and Icarus were produced using light curve inversion techniques These are believed to be the first such models for these asteroids. VIII Chapter 1 Introduction Threats to homeland security come in many forms. Most people, when they hear the words “homeland security”, immediately think of terrorism and the many threats it poses to homeland security: radiological threats, chemical threats, biological threats, and terrorist attacks such as those we have seen in the past (the coordinated attacks using airplanes on September 11, 2001) or the more recent attacks overseas such as the shootings in France. However, there are other threats to the security of the United States homeland that can be just as, if not more, devastating than terrorism. Included among these are threats related to devastating weather events and the potential of an asteroid collision with Earth. Background We only have to look at the landscape of our planet or that of the moon to see the evidence that impacts from bodies from space is part of our planet’s history and likely its future. There are 170 established impact craters on earth’s exposed land surface (Space Studies Board of the National Research Council, 2008). It is estimated that impacts from small asteroids occur at a rate of 5-10 events per year ("Interactive Map of Meteor Strikes", 2017). Most of these go unnoticed as small objects disintegrate before reaching the ground. If the object does survive the journey through earth’s atmosphere, it is statistically more likely to land in the ocean than on land. From meteor observations, small dust and stony fragments strike our atmosphere resulting in a momentary burst of light at a rate of about 1,000 visible meteors per second across the planet. Larger fragments entering earth’s atmosphere are observed as extremely brilliant meteor-like flashes. Fireballs are meteors 1 of magnitude –4 or brighter on the standard astronomical magnitude scale. Bolide events are observed as a brilliant flash of light of magnitude -14 or brighter and super-bolide events are of -17 or brighter magnitude. Meteoroids larger than 1 m are capable of penetrating the earth’s atmosphere deep enough to result in an airburst, an event in which the entering objects explodes releasing large amounts of energy comparable to a TNT explosion (Barentsen, 2013). The energy released in an explosion of one ton of TNT is approximately 4.2x1015 joules. The standard unit of energy in describing impact event is given in terms of kilotons of TNT. There is an inverse relationship between object size and impact frequency. From analysis of lunar craters, impact frequency decreases proportionally to the cube of the diameter