Want to pitch in to help discover unknown planets?

Astronomers are inviting the public to participate in a search for planets orbiting other stars in our galaxy.

Researchers working on a project called the Next Generation Transit Survey are inviting the public to help to scan five years of data from telescopes observing nearby stars, looking for tell-tale signs of orbiting planets. 

Using the citizen science platform Zooniverse, they have launched a project called Planet Hunters NGTS, which allows volunteers to  participate in the search for other worlds.

The data comes from a cluster of twelve small robotic telescopes in the high Atacama desert of northern Chile, at the same site as the European Southern Observatory. Every night they scan the skies measuring the brightness of stars, looking for changes that might indicate the presence of a planet. 

This illustration and graph shows how an exoplanet passing in front of its star causes the brightness of the star to decrease. (NASA)

Unfortunately, planets beyond our solar system are almost impossible to see directly because they are dim and tend to get lost in the glare of their parent star, like trying to see a firefly next to a searchlight from several kilometres away. That may change with the launch of the new James Webb Space Telescope in December, which may be able to resolve images of planets directly.

But in the meantime, the primary way planets give away their presence to astronomers is by blocking a portion of the light of their star as they pass in front of it, which is called a transit.

A transit can only be seen when the plane of a distant solar system is aligned edge-on to us, so planets orbiting a star can pass in front of it from our point of view on Earth. A small percentage of the star is blocked by the planet, so light from the star is slightly reduced until the planet passes, then it gets brighter again. 

The Next Generation Transit Survey telescopes take images of the sky every ten seconds. The brightness of the stars observed then gets plotted on a graph. The plot begins as a more or less flat line, but if a planet is present, the line develops a U-shaped dip as the light goes down and back up again. The width of the U tells you how long the planet was in front of the star, and the depth tells you how much light was blocked out so you can estimate the planet’s size. 

An example of a graph presented for volunteers to interpret from the Planet Hunters NGTS site. This shows a u-shaped drop in the graph of light received by the telescope. (Planet Hunters NGTS)

This transit method is one of the primary methods astronomers use to spot planets, using telescopes on the ground and in space. It has allowed them to find more than 4000 exoplanets so far.

With the NGTS project, computer algorithms monitor the output from the telescopes and flag suspicious dips in the light. It turns out that most of these changes in starlight are not caused by planets, so astronomers then examine graphs of the data by eye to identify the best candidates. Humans, it seems, are still better than computers when it comes to the kind of pattern recognition that is involved in this task. The most promising possibilities can then be followed up with further observations with more powerful telescopes to see if a planet is really there.

This is where the public comes in. The Next Generation Transit Survey telescopes have been observing since 2016 and looked at hundreds of thousands of stars, so there’s a lot of data. Scientists would like more eyes to examine the plots to see if any planets are hiding there. 

Participation is free, and just involves looking at graphs on the website. This could be a chance to be part of the discovery of another world.

This particular survey is looking for planets the size of Neptune or smaller, with diameters between two and eight times that of Earth. These are the best candidates for the holy grail of planet hunters: an Earth-sized planet going around a sun-like star at just the right distance so life could exist on its surface. 

This isn’t even your only chance to help discover exoplanets.  This is a sibling project to the Planet Hunters TESS project that allows the public to help comb through data from the space-based Transiting Exoplanet Survey Satellite.

A study by Michelle Kunimoto and  Jaymie Matthews from the University of British Columbia has suggested there could be up to six billion Earth-like planets in our galaxy, but so far, an twin to the Earth has not been found. Most exoplanets are either giants like Jupiter, orbit extremely close to their stars making them super hot, or go around very dim red dwarf stars that are quite different from our sun. Solar systems like ours could be quite rare.

And of course any Earth-like planet that we discover will be very far away from here, farther than our current rockets can reach. Which makes this beautiful blue orb we live on even more special.

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