The Interplanetary Travel Guide

The last couple of weeks have seen exciting developments in exoplanet astronomy. After 3 years of observations, astronomers at the European Southern Observatory discovered a planet orbiting the closest star system to our own Sun. Detecting this Earth-mass planet required measuring the velocity changes of Alpha Centauri B to a remarkable accuracy of 51cm/s (or 1.1mph). Not only was this the closest exoplanet yet found, it was also one of the smallest, with a minimum mass only 1.3 times that of Earth. However, this rocky world orbits so close to its star that day-side surface temperatures are likely to be around 1500K. Not exactly a habitable world, but it shows that exoplanet astronomy is progressing towards finding Earth-like worlds.

Another planetary discovery, announced on Thursday, appears to be a much better candidate for life. This planetary system, around 32 light years away, contains six planets orbiting the dim star HD40307. One of these planets, a super-Earth orbiting at 0.6AU, has a surface temperature of between -17° and 52°C. Although more than 7 times the mass of Earth, such a planet may have the potential to support life.

These discoveries have generated lots of talk about interplanetary exploration, especially along the lines of 'Lets drop everything and send humans and spaceships to these planetary systems!'. However, the gulf of space is unimaginably huge. Even with the fastest spacecraft ever built by humans, Voyager 1, it would take 70,000 years to get to Alpha Centauri B. If the distance between Earth and the Sun were scaled to fit in the palm of your hand, the nearest star would be 13 kilometres away! So what would humanity need to actually get there? Here is, entirely in my own view as a student of exoplanets, what we need to do to send a space-probe to another planet.

1. Find them all. With space missions like Gaia and ground-based scans like HARVPS & MEarth we could probably find all the earth-like planets around local stars by 2030.
2. Get a closer look. If the planet passes between us and its star (transits) we can get a glimpse at its atmosphere using something like JWST or EChO. Non-transiting exoplanets like this one are a little tougher, but projects such as TPF and Darwin will be able to image them and check their atmospheres for oxygen & water. Timeframe: by 2040.
3. Explore the solar system. Sending humans to an asteroid, and eventually Mars is just as important in the interplanetary space race. There's not going to be any appetite for space travel if we don't keep exploring our own solar system. Timeframe: by 2050


Sending a probe 10 light years in a human lifetime is going to take some big technological developments including:


4. Laser-powered Nuclear Fusion. This looks, according to an old UK study called Daedalus, to be the best bet for fuel on an interplanetary spacecraft, achieving speeds up to 12% of the speed of light (0.12c). Timeframe: 2030
5. Cheap launches to Earth-orbit. To assemble such a large craft in orbit will require cheap delivery to ever be feasible. Timeframe: 2040+
6. Earth-orbit refuelling and asteroid mining. Timeframe (if Planetary Resources are to be believed): 2020
7. Global Cooperation. Unless one country wants to be shackled with the most expensive mission ever, we're gonna need everyone involved. Timeframe: never?.
8. Mining the materials, building the parts, organising thousands of rocket launches and finally assembling more than 50,000 metric tonnes of metal and fuel into a spacecraft that might take a lifetime to reach the nearest stars and cant even stop or slow down at the other end. Timeframe: 2100+

So there's lots to do, and everyone can get involved! I'm going to concentrate on 1 & 2 for now by writing some code for my project on the Exoplanet Characterisation Observatory (EChO), but probably the best way to help our species get to another planet is to support science! Only if scientific agencies like NASA and ESA are widely supported by the public and adequately funded will such a project ever get off the ground.