Relativistic Gas Drag on Dust Grains and Implications

Abstract

We study the drag force on dust grains moving at relativistic velocities through interstellar gas and explore its application. First, we derive a new analytical formula of the drag force at high energies and find that it is significantly reduced compared to the classical model. Second, we apply the obtained drag force to calculate the terminal velocities of interstellar grains by strong radiation sources such as supernovae and active galactic nuclei (AGNs). We find that grains can be accelerated to relativistic velocities by very luminous AGNs. We then quantify the deceleration of relativistic spacecraft proposed by the Breakthrough Starshot initiative due to gas drag on a relativistic lightsail. We find that the spacecraft's slowing down is negligible because of the suppression of gas drag at relativistic velocities, suggesting that the lightsail may be open for communication during its journey to $\alpha$ Centauri without causing a considerable delay. Finally, we show that the damage to relativistic thin lightsails by interstellar dust is a minor effect.

arXiv commentApJ, in press; 7 pages, 5 figures

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Cited by in corpus (13)

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• Propulsion of Spacecrafts to Relativistic Speeds Using Natural Astrophysical Sources
• Dust Destruction by Drift-Induced Sputtering in Active Galactic Nuclei
• Electromagnetic forces on a relativistic spacecraft in the interstellar medium
• Challenges in Scientific Data Communication from Low-Mass Interstellar Probes
• Modeling rotational disruption of grains and microwave emission from spinning dust in AGB envelopes
• Rotational disruption of dust grains by mechanical torques for high-velocity gas-grain collisions
• Photogravimagnetic assists of light sails: a mixed blessing for Breakthrough Starshot?
• A covariant formulation of relativistic mechanics
• Constraints on the abundance of $0.01c$ stellar engines in the Milky Way
• Galactic Traversability: A New Concept for Extragalactic SETI
• Rotational Disruption of Dust and Ice by Radiative Torques in Protoplanetary Disks and Implications for Observations