2. 2 Launched on 19 th Jan 2006 Orbits 39.5 AU from Sun (1 AU is average Earth-Sun distance) Journey of 3,463 days = 9.48 years 4,760,000,000 km journey (~3 billion miles) Pluto flyby on 14 th Jul 2015 at 12,500 km 33.39 AU = 4.5 light-hours from Sun Where next?

3. 3 Discovered 26 th Jun 2014 by HST Magnitude +26 Orbits 44.2 AU from Sun, Period 293 years Low inclination and eccentricity – classic KBO Estimated diameter 30-45 km Flyby on either 31 st Dec 2018 or 1 st Jan 2019 43.4 AU from Sun at flyby Where Next?

4. 4 Where would we like to go? – Nearest star! – ‘Interesting’ star!! – Earth-like exoplanet!!! – Across the galaxy!!!! – Another galaxy!!!!! Can we?

5. 5 Speed of light, c = 1 ly/yr Destination Distance, d (ly)Time, t (yr)Speed, v (ly/yr) Pluto0.000630.035 0.036 Proxima Centauri4.242.866 2.959 Vega24.046.825 7.045 Kepler-452b1,40052.081 53.763 Across Galaxy100,000440.162 454.378 Andromeda Galaxy2,500,0002,200.812 2,271.888 Destination Distance, d (ly)Time, t (yr) Pluto0.000630.035 Proxima Centauri4.242.866 Vega24.046.825 Kepler-452b1,40052.081 Across Galaxy100,000440.162 Andromeda Galaxy2,500,0002,200.812 Destination Distance, d (ly) Pluto0.00063 Proxima Centauri4.24 Vega24.04 Kepler-452b1,400 Across Galaxy100,000 Andromeda Galaxy2,500,000 Let’s assume we can maintain a continuous acceleration of 1g = 9.81 m/s 2 = 1.0323 ly/yr 2

6. 6 Special relativity becomes important!

7. 7 Destination Distance, d (ly) Time on Earth, t (yr) Time on Rocket, T (yr) Speed at Destination, v (ly/yr) Pluto0.000630.035 0.03603439122399 Proxima Centauri4.245.1202.2960.98248961191519 Vega24.0424.9923.8270.99924629467535 Kepler-452b1,4001,400.9717.7360.99999975987502 Across Galaxy100,000100,000.97111.8790.99999999995287 Andromeda Galaxy2,500,0002,500,000.97115.0040.99999999999993 Special relativity becomes important very quickly! But… this for a fast flyby – no slowing down! Almost no time to view destination Radio signals back to Earth highly red-shifted

8. 8 Destination Distance, d (ly) Time on Earth, t (yr) Time on Rocket, T (yr) Pluto0.000630.049 Proxima Centauri4.245.869 3.545 Vega24.0425.9096.380 Kepler-452b1,4001,401.94014.127 Across Galaxy100,000100,001.94222.413 Andromeda Galaxy2,500,0002,500,001.94228.663 Suppose we want to slow down to arrive at our destination at low speed? This is just ‘fiddling with numbers’ – what about the engine and fuel?

9. 9 Consider our options… – Chemical fuel – Nuclear fuel – Matter/Anti-Matter Annihilation – Gamma-ray Lasers (Grazers) – Star-Trek Warp drives Wormholes Black-hole slingshots

10. 10 Destination Distance, d (ly) Fuel Mass per kg of Payload Pluto0.000630.05 kg Proxima Centauri4.2437.52 kg Vega24.04713.16 kg Kepler-452b1,4002,085.13 tonnes Across Galaxy100,00010,609,412.00 tonnes Andromeda Galaxy2,500,0006,630,635,300.00 tonnes Assume we can convert matter to energy with 100% efficiency! How much matter do we need?

11. 11 Engine/Fuel not possible! – Wait for Star Trek solution? Slower travel possible (<1g) – Robotic Missions Only? – How many human generations? Shielding is an issue! – Interstellar dust – Cosmic Microwave Background Returning signals to Earth – Size of dish and power required – Delay between departure and signals returned!

12. Inspired by ‘The Relativistic Rocket’ http://math.ucr.edu/home/baez/physics/ Relativity/SR/Rocket/rocket.html