Earth Mark II: Kepler finds further habitable exoplanets


It’s funny how can slip past you.

It wasn’t so long ago that we were hearing a lot about newly discovered exoplanets, or extrasolar planets – planets not in our solar system. It transpires that one of the main instruments used to search for them, namely NASA’s Kepler space telescope, incurred a major problem.

One of its four reaction wheels – the parts of the satellite responsible for maintaining altitude – failed. This meant the ability of Kepler to stay perfectly stable whilst taking pictures was seriously impeded.

Luckily however, with a bit of engineering genius, the planet hunter is back.

Amongst the first results from the newly revived Kepler is what is claimed to be the most Earth-like exoplanet ever discovered, Kepler-438b.

The principle behind catching an exoplanet is to analyse the light output from a large number of stars. When the intensity dips in a characteristic way, an exoplanet has been found. Unfortunately, there are limitations. This method, known as the transit method, only works when the plane of an observed extrasolar system is just in the right inclination.

Given this, and the now limited ability of Kepler to observe, it is a minor miracle that three new Earth-like planets have been discovered.

Kepler-438b, Kepler-442b and the equally imaginatively named Kepler-440b have now been added to the existing five exoplanets that are of similar size to Earth and exist in the habitable-zone, where liquid water and water vapour are thought to coexist.

But why are we trying to find these Earth-like exoplanets? Is it within the realm of possibility that we will ever travel there?

If we are to believe popular culture – movies such as Interstellar and much before it, A Space Odyssey – interplanetary travel is no more than waiting for a cataclysmic event and being in the right place at the right time.

There are many problems with travelling long distances in space.

Kepler-438b is 475 light years away; even if it was possible to travel at the speed of light, it would take 475 years to get there. Clearly it would be several generations before the planet is reached, and who knows if it would be any good anyway?

Then there’s the slight issue of radiation. The earth protects us from a great proportion of harmful ultraviolet radiation from the Sun with its unique atmosphere. This is easily blocked by a simple sheet of glass, but in space, there are more harmful gamma rays that can only be stopped by several centimetres of lead (not conducive to building a light spacecraft). Outside of the Sun’s sphere of influence, things get even worse.

Finally, propulsion must be considered.

Whilst it is true that the vast majority of fuel in a spacecraft is used to get into orbit, we would want to get to this new planet in a reasonable timescale. This means speeding up to near relativistic speeds, then slowing down again when the target planet is reached. All of this requires fuel.

Maybe one day, with advanced propulsion systems or a loophole in physics, these planets will be within our grasp.

Presently however, over forty years have passed since the last Moon landing. Perhaps it would be best to take baby steps and explore our own back garden before venturing further.

Image: Kanijoman on flickr

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