The search for a New Earth

In the event of a nuclear war or catastrophic climate change, humanity may be forced to up sticks and find another planet to settle down on. Are there any candidates? Part of our series on York Science Week

The Kepler Telescope on the horizon, taken from the International SPace Station. Image: NASA's Marshall Space Flight Center

The Kepler Telescope on the horizon, taken from the International Space Station. Kepler scanned the skies for 3 years looking for other planets.
Image: NASA’s Marshall Space Flight Center

As a part of the University of York science week, a talk was conducted by Dr Emily Brunsden, entitled ‘The Problem with Planets’.

As a biochemistry student with only a GCSE-level understanding of Physics under my belt, I was nervous that I would be sat there pen in hand, listening attentively to ideas and theories that I couldn’t spell, let alone understand. The man with a NASA cap placed jauntily upon his bald head two rows down did nothing to quell my fears.

I was however pleasantly surprised. The event was a perfect example of what the entire scientific community strives to do: presenting a current and complex topic so that it is wholly understandable and engaging for the general public.

Now for the exploration of how and what has been discovered in the search for planets beyond our solar system. The discussion started with the approaches preferentially used for detecting the presence of planets, and what data could be gathered from these techniques.

Reflex motion detection, for example, is a technique that looks for how much a host star wobbles. Our solar system exists because of planets interacting with our host star’s – the Sun’s – gravitational pull. Stars are not immune to the gravitational pull of their surrounding planets, and therefore as the planet orbits its star, the star wobbles. When the star moves towards us, it becomes bluer, and further away, redder due to the Doppler Effect. This is detected by a telescope: the best in the world in fact, containing a 3.6 metre diameter mirror with a light detector mounted on it.

Another technique, called ‘Light curves detection’, relies upon the extremely small probability of a planet crossing between Earth and a star. In the event that this does happen, a miniscule amount of the star’s light is blocked, proportional to the planet’s diameter. Until recently, this was detected by the best piece of planet-finding equipment we have had to date – the Kepler telescope. The instrumentation was built with a three year guarantee, it made it to the three year and one day mark, and then it gave up the ghost. The loss of this detector will almost certainly significantly lower the number of planets found in the next few years. NASA and ESA both have projects in the pipeline – TESS and PLATO respectively – which are detectors similar to Kepler, surveying the brighter stars in the sky for any changes.

Since 1992, 1849 planets and 471 systems have been confirmed. 850 of these have been found so far this year, and the year isn’t even over. The larger the planet, the easier it is to detect, so many of these are large, hot, Jupiter-sized planets.

It is universal hope that we will find a planet which either has or at least holds the potential to support life. The illusive ‘Planet B’ must be out there. For a planet to have the capacity for life, it must be within a certain range of distance from its host star, depending on the star surface temperature, for water to exist as liquid. This has been the coined the ‘Goldilocks Zone’.

Many planets have been identified as ‘similar’ to Earth, but the truth is that so little data can be collected to form a comparison. At present, the planets are simply spheres in space, which artists have great fun producing ‘representations’ of. One of the most Earth-like is called Gliese 832c which is 16 light years away and is part of a system which has 2 planets confirmed. Its host star has a surface temperature of 3600 degrees Celsius compared with 5600 of our sun, and the planet’s mass is five times that of the Earth’s. This planet is 16 light years away, it would take millennia to send technology there to see whether the elemental make-up is supportive of life, but the knowledge that there could be a ‘New Earth’ keeps scientists going to find more.

This planet we call home is special, at least in the near vicinity. If there is another one, it’s highly unlikely we can get to it in the unforeseeable future. Let’s look after what we’ve got.

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