Alien-hunters to search over 200,000 new stars

Expect the unexpected: What alien life may look like. © iStock. © iStock

Are aliens hiding in plain sight? Scientists are widening the search for life on other planets, but some argue we will never find it because we have no idea of what we are looking for.

The hunt for alien life has just got a lot bigger. The Breakthrough Listen project to find signals sent by intelligent life has widened its search of our galactic neighbourhood: from 1,400 to 280,000 stars. This increase is made possible by the groundbreaking work of the Gaia spacecraft.

Of course, scientists do not expect all aliens to be sending radio signals. Humans only began to do this in the last century and astrobiologists believe most alien life is not intelligent. They also say we need to be looking a lot closer to home, maybe even on Earth itself.

Life on Earth is carbon based and has adapted to a watery environment. However, Nasa defines life as “a self-sustaining chemical system capable of Darwinian evolution”. This broader definition could include life composed of silicon.

If this is possible, astrobiologists speculate that we may discover aliens here on Earth, hiding in the Earth’s crust.

The traditional idea of individual aliens may be too geocentric. Planetary scientist Stuart Bartlett thinks we need to rethink our definition of life. He has devised a new concept: lyfe. This is a process that draws energy from its environment, grows exponentially, regulates itself and has the ability to learn.

So are aliens hiding in plain sight?

Close encounters

Some say no, aliens are not all around us. Scientists have been listening for signs of intelligent life for fifty years without success. Changing the definition of life makes the search for aliens meaningless because then they could be whatever we want them to be — even silicon microbes hiding on Earth.

Others say yes, we should not assume that aliens will look like us. We have evolved over billions of years to become adapted to living on Earth. Life on planets will most likely take on completely different forms beyond our imagination.

You Decide

  1. Is there alien life in the universe?


  1. Draw a picture of an alien.

Some People Say...

“Space, the mirror, waits for life to come look for itself there.”

Ray Bradbury (1920 -2012), American author

What do you think?

Q & A

What do we know?
It is generally agreed that alien life exists on other planets. Whilst it is possible we are alone in the universe, astrobiologists consider this highly unlikely. There are an estimated six billion Earth-like planets in our galaxy alone and there may be as many as two trillion galaxies in the universe. To be considered Earth-like, a planet must by rocky and orbit a Sun-like star at a habitable distance that can host liquid water and potentially life.
What do we not know?
One main area of debate is around whether theories help or hinder scientific discovery. On the one hand, testing theories against the evidence is how science progresses from ignorance to knowledge. However, in the search for extraterrestrial life, some argue we should “expect the unexpected.” This is easier said than done. Philosophers argue that our theories, concepts and beliefs all affect what we are able to see and understand.

Word Watch

Breakthrough Listen
Leading astrophysicists, including Stephen Hawking, set up this project in 2015 to dedicate thousands of hours of telescope time to search for extraterrestrial life. The main telescopes are Green Bank in the US and Parkes Observatory in Australia.
Gaia spacecraft
Launched in 2013, Gaia is currently cataloguing approximately one billion stars, planets, comets and asteroids in the most detailed astronomical map ever created.
The search for extraterrestrial life is often narrowed down to so-called Goldilocks zones, planets that are not too hot and not too cold.
Darwinian evolution
Some form of reproduction with variation or mutation is required for life to adapt to its environment and grow in complexity.
Scientists have managed to create carbon-silicon proteins in the laboratory, but complex silicon aliens would have very unusual biochemistry. Due to how silicon reacts with oxygen, one theory suggests silicon-based life forms would breathe out quartz rock.
The popular image of “little green men” is a good example of this. Our ideas about what alien life looks like are based on our experience and expectations of life on Earth.
Darwinian evolution is a form of storing information in genes, but it is not the only way life adapts to its environment.

PDF Download

Please click on "Print view" at the top of the page to see a print friendly version of the article.