Cosmic Hazard Forecast: Near-Earth Supernovae & Gamma-Ray Burst Rates 🌌

Project Overview

This repository contains the code and datasets used in the research "Cosmic Hazard Forecast: Rates of Near-Earth Supernovae and Gamma-Ray Bursts" by Brian Fields, Danylo Sovgut, Ashvini Krishnan, and Alexandra Trauth. The study presents a model for estimating the rate Γ(𝑟) of cosmic explosions (supernovae & GRBs) as a function of distance from Earth.

Cosmic explosions have potential implications for Earth's biosphere, mass extinctions, and the Galactic Habitable Zone. The code within this repository generates datasets, performs numerical integration, and produces plots that explore these astrophysical threats.

🔬 Research Motivation

• Supernovae (SNe) & GRBs are among the most energetic cosmic events and can influence planetary environments.
• Nearby explosions may threaten Earth's biosphere, potentially causing ozone depletion and increased radiation exposure.
• Understanding the frequency and distribution of these events provides insights into habitability conditions across the Milky Way.

📊 Key Objectives

• Model the rate of supernovae & GRBs as a function of distance from Earth.
• Compare explosion rates from different galactic distributions:
  • TRILEGAL model (stellar distribution-based rate)
  • Green's model (SNR-based rate)
• Incorporate statistical clustering effects for explosion progenitors.
• Evaluate the threat level from cosmic explosions based on their kill distances.

🛠️ Methodology & Model Framework

1. Explosion Rate Density

• The local event rate Γ(𝑟) is derived by integrating the explosion rate density over a spherical volume.
• Axisymmetric models distinguish between thin disk (CCSN, LGRB) and thick disk (SGRB, Type Ia SN) events.
• Rates are computed for two galaxy models:
  • TRILEGAL Model (follows galactic stellar density)
  • Green Model (based on supernova remnant distribution)

2. Local Explosion Rate Calculation

• Integrates over galactocentric coordinates (𝑅, 𝑧) to compute the local explosion rate near Earth.
• Models consider solar position and vertical oscillations in the Galactic plane.

3. Clustering Effects

• Cosmic explosions occur in stellar clusters, affecting the mean time between nearby events.
• Adjustments made to reflect clustered supernova rates.

4. Defining Cosmic Hazard: Kill Distances

• A cosmic explosion is hazardous if it depletes ≥30% of the ozone layer.
• Defined kill distances for each explosion type:
  • Core-Collapse Supernovae (CCSN): 10 pc
  • Long Gamma-Ray Bursts (LGRB): 2044 pc
  • Short Gamma-Ray Bursts (SGRB): 91.4 pc
  • Type Ia Supernovae: 10 pc

📂 Computational Components

1. Data Generation Scripts

• generate_trilegal_rates.py: Computes rates for TRILEGAL model.
• generate_isotope_rates.py: Computes isotope model rates (Fe-60 & Al-26 contributions).
• generate_solar_height_rates.py: Explores CCSN & Type Ia SN rate variations with solar height.

2. Calculation Modules

• mean_times.py: Computes mean recurrence times of explosions.
• galactic_center_rates.py: Estimates explosion rates near the Milky Way’s center.

3. Plotting Scripts

• rate_vs_distance_trilegal.py: Generates explosion rate vs. distance plots.
• rate_vs_distance_isotope.py: Compares Trilegal vs. Isotope model.
• rate_vs_extinctions.py: Analyzes correlation between explosion rates and mass extinctions.
• historical_sn_comparison.py: Compares model predictions with historical supernova records.

📈 Key Findings

• The CCSN & LGRB rates are the most significant for potential biospheric impact.
• The mean recurrence time for a near-Earth CCSN event is ~2.4 Gyr.
• A near-Earth LGRB event is rarer (~0.7 Gyr mean time), but far more catastrophic.
• SGRB & Type Ia SN pose lower risks due to their infrequent occurrence.
• Mass extinction events may be correlated with historical supernova activity.

🌍 Implications & Future Work

• The results suggest that cosmic explosions could play a role in Earth’s extinction events.
• This framework could be used to map galactic habitability zones, evaluating where planetary biospheres are least at risk.
• Future improvements:
  • Refine stellar clustering models for CCSN rates.
  • Integrate spiral arm dynamics into supernova rate distributions.
  • Extend models to include external galaxies & cosmic ray exposure.

---

🔹 Authors: Danylo Sovgut, Brian Fields, Ashvini Krishnan, Alexandra Trauth
🔹 This research is affiliated with the University of Illinois at Urbana-Champaign, Department of Astronomy.