1. What is High-Energy Astrophysics? What is studied by high-energy astrophysicists: Supernovae Supernovae remnants Pulsars/magnetars Gamma-ray bursts Accreting compact binary systems Active galactic nuclei

2. Supernova 1994D in galaxy NGC 4526

3. Cass A supernova remnant observed in X-rays

4. Pulsar and sur- rounding nebula in the Crab supernova remnant.

5. Nucleus and jet in the middle of the galaxy M87. Imaged in visible light with the Hubble Space Telescope.

6. What is High-Energy Astrophysics? What is studied by high-energy astrophysicists. Study of energetic/violent phenomena in the universe (T > 10 5 K; hottest photospheres). Astronomy done with X-ray and γ-ray photons, charged particles (cosmic rays), neutrinos, and (someday) gravitational radiation.

7. Electromagnetic Spectrum Region λ photon E Equivalent Temp (nm) (K) Extreme ultraviolet 100 – 10 12 – 120 eV 1.4 x 10 5 – 1.4 x 10 6 Soft X-ray 10 – 1 120 – 1200 eV 1.4 x 10 6 – 1.4 x 10 7 (hard) X-ray 1 – 0.01 1.2 – 120 keV 1.4 x 10 7 – 1.4 x 10 9 Soft γ-ray 0.01− 0.001 120 – 1200 keV 1.4 x 10 9 – 1.4 x 10 10 γ-ray 1.2 MeV > 1.4 x 10 10 Photon energy = hν (maximum observed ≈ 10 TeV) Equivalent temperature = hν/k 1 electron volt = 1 eV = 1.602 x 10 -12 erg Boltzmann constant = k = 8.61 x 10 -5 eV/K 1 GeV = 10 9 eV; 1 TeV = 10 12 eV (tera); 1 PeV = 10 15 eV (peta)