Thomas Plunkett spent two years working out whether three possible planets detected around distant stars were really there. Two were.
The University of Tasmania astronomer and School of Natural Sciences PhD candidate led follow-up observations from Greenhill Observatory in Tasmania's Midlands, helping confirm two giant planets on orbits unlike anything in our solar system. Each circles its star in about three days.
The work marks the first time in a decade that observations from a Tasmanian observatory have played a key role in confirming new planets beyond our solar system.
The possible planets were first identified by NASA's Transiting Exoplanet Survey Satellite (TESS), which searches for tiny, regular dips in starlight that may occur when a planet passes in front of its star.
Using Greenhill Observatory, Mr Plunkett and his colleagues measured the brightness of the stars over time, looking for the repeated dips caused when a planet passes in front of its star. Those observations helped the team determine whether the signals were caused by planets and calculate their size.
Both confirmed planets orbit remarkably close to their stars. One is a giant gas planet, similar to Jupiter. The other appears unusually inflated, swollen by the heat of its nearby star and less dense than astronomers would expect.
A third possible planet examined by the team remains unconfirmed.
Astronomers have discovered thousands of planets orbiting stars beyond our Sun. Researchers are now trying to understand what those discoveries reveal about how planetary systems form and change over time.
"Hot giant planets are rare in nature and are found around fewer than one per cent of stars," Mr Plunkett said.
"They are reasonably easy to find using the transit method, but that reflects the way we observe them rather than how common they are.
"The highly inflated planet is particularly unusual. Planets like these are important because they can help us understand how planets migrate and evolve over time."
The study brought together observations from Tasmania and collaborators across Australia, North America, Europe and South America.
"The first hint of a planet might come from a spacecraft," Mr Plunkett said.
"But it takes observations from the ground to work out what you're actually looking at. That's where Greenhill has been able to contribute."
The study, The TASSIE Program II: Three Close-In Companions Orbiting Sun-Like Stars , was published in Publications of the Astronomical Society of Australia.
