A report on the May 2025 Society Meeting talk prepared by Dave Allen.
It was around 70,000 years ago that Homo Sapiens began to venture out of the African continent and explore lands and seas far beyond, to look for new places to live and thrive – since that time we have settled in all continents, we have built societies and cultures, we have adapted and thrived – but it is in our make up to explore and discover.
The famous poet TS Eliot once quoted ‘We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.’
So now we are looking to explore even more beyond the comfort of planet Earth and find what is out there.
Dr Matthew Bothwell who is the public Astronomer at Cambridge University gave us an interesting talk called ‘Searching for Earth 2.0 – Exoplanets and Life in the Universe’.
Is there life out there? Is there a habitable planet that humans could one day live on?
Those are the questions to be answered – Dr Bothwell explained that we have been looking at the night sky for thousands of years trying to understand the stars.
In Western Astronomy, the ancient Greeks first realised that there are two different types of stars. Most of the 3000 or so stars we can see in the night sky are what is called fixed stars, stars that stayed in the same place night after night. A constellation would be in the same place relevant to the Earth spinning.
But there are also a handful of stars that move around called ‘wandering stars’.
He explained how we search for new planets (exoplanets) in other Solar systems. You could build the largest telescope and look carefully, but this is very difficult as a star is very bright and a possible planet is tiny. An analogy would be you are looking at the light of the brightest lighthouse and trying to find the smallest firefly; you would never see the firefly as the light from the lighthouse would just blind you.
The two ways that might work for hunting exoplanets are called Wobbles (Doppler shifts) and Shadows (Transits).
Matthew explained that the Wobble (Doppler shift) method is all about Gravity. The planet will pull on the star using its Gravitational pull which will cause the star to wobble which then will mean there is a hidden planet near the star.
The first exoplanet found this way was in 1995 and named Pegasus B as it orbited the Star called Pegasus 51. The exoplanet is a gas giant about the same size as Saturn, but it is so close to its parent star that one orbit takes only four days, in other words a year on this planet is just four days long. Pegasus B would not be habitable for us.
The Shadow (transit) method is looking for a shadow to appear blocking a small amount of light from the star. If the light dips this confirms there is a hidden planet moving across the path of the star.
Since that first exoplanet was discovered in 1995, we now know of over 5000 exoplanets out there.
Matthew told us what the future will look like in this field. There are plans for a very powerful telescope called PLATO to be used for exoplanet hunting, and it is anticipated that we will be discovering many more thousands of exoplanets out there.
We want to study exoplanets much more to see if life exists there. Is the temperature just right for life to exist? Can we live there one day? The exoplanet needs to be in the habitable Zone or as we call it ‘the Goldilocks Zone’ just like Earth in our own Solar System.
Small habitable planets may be very rare out there in the Universe. At present we know of 21 of them in the habitable zone where life may be possible. All of these have been found only in the past few years.
Matthew finished by explaining even if we find a planet soon that is just right for us, for life to exist as we know it, it may be so far away that with our current technology it would take thousands of years to get there!!
But, in all those millennia after millennia since we left Africa, Homo Sapiens have achieved so much and gained so much knowledge. Who knows what we can achieve – here’s to the next 70000 years.