WHAT do you do in retirement? Take up golf, play bowls, solve crosswords, grow vegetables, join Probus?
That’s what most of us do, but not Mr Thiam-Guan (TG) Tan. Before retirement he worked for Shell as an engineer for 36 years, now he finds new planets, round stars (exo-planets).
TG and wife Janet bought their Mount Claremont home because it has a wide field of view over the sky. He has installed a 12” optical telescope in a shed in this back yard. The shed slides away to reveal his telescope and computer.
“Perth is a great place for astronomy,” he says. “But not in winter when the clouds obscure the stars. In summer there are great starry nights.
“Light pollution is not an important problem for my work. I’m looking for brightness.”
Stars with planets periodically dim as the planet comes between the earth and the star, provided the planet’s orbit in the same plane as the earth.
“It is also important that the planet is orbiting its star fast enough to observe several passes. Otherwise it would take many years to confirm the star’s dip in brightness. It also needs to block enough light.”
TG can observe a star dimming by as little as 0.5 per cent.
“The size of this dip tells you how big the planet is,” he says.
He passes the information on to major observatories that use much bigger telescopes to measure the ‘wobble’ in the star as the planet goes around it. This allows astronomers to calculate its mass.
TG’s findings are confirmed by spectrographs – instruments that separate light into a frequency spectrum and then record the signal using a camera. The HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph at the European Southern Observatory in Chile confirmed TG‘s initial discovery of the most exciting exo-planet yet found in the search for alien life.
“It is a small planet going round a small star. The planet is 1.6 times as big as the earth and its star, a red dwarf, only produces 13 per cent of the light of our sun.
“At just 40 light years away it is the closest earth-like planet found so far.”
The planet is named LHS 1140b. It appears to have a dense metal core, like the earth and this suggests it might have once had an ocean.
“The first planet was identified in 1975, we now know there are many more,” TG said.
Earlier planet finders could survey only a small section of the sky. Now wide area surveys are providing lots of data on over one million stars.
“There are 100 billion stars in the Milky Way (our galaxy) alone and billions of galaxies in the universe.”
The NASA Kepler space telescope launched in 2009 is designed to find earth-like planets orbiting a star and has so far discovered more than 1200, including several earth like rocky planets orbiting their star in the goldilocks zone – not too hot and not too cold for liquid water.
“We estimate that on average each star has at least one planet, so there are 100 billion or more planets in our galaxy. It is also harder to find small planets so the number of earth-like planets could be an under-estimate.
“My personal view is that there is probably life of some sort on at least some planets. We can detect lots of earth-like planets and we know water, which is essential for life, is plentiful on them.”
TG has co-discovered 28 planets so far in his seven years of searching the heavens.
“The first discovery was big news, but it’s now less so as the rate of discovery increases. A new find is only reported if it is special enough,” he said.
But it is special to think that a retired Perth engineer may have found the first hint that we are not alone in the universe.