An Australian university student has co-led the discovery of an Earth-sized, potentially habitable planet just 40 light years away.
Shishir Dholakia, a PhD candidate in astrophysics at the University of Southern Queensland, is part of an international team that published the discovery in the Monthly Notices of the Royal Astronomical Society.
He described the “Eureka moment” of finding the planet, which has been named Gliese 12b.
“We did the back-of-the envelope calculations,” he said. “We worked out it’s probably Earth-sized, it’s probably temperate, and that it’s really, really nearby. In the span of a day we were like, ‘Oh, we have to write this up. This is something really cool.’
“It could be at the right temperature for liquid water to pool on the surface … [that’s] important because we think planets are potentially habitable if they can have liquid water on them.
“And so in this great search for life that we’re undertaking we want to try to find planets that are potentially habitable, and this could be a good contender.”
Gliese 12b is the size of Earth or slightly smaller, like Venus. And its surface temperature is estimated to be a balmy 42C.
Its 12-day orbit is around Gliese 12, a cool red dwarf in the Pisces constellation. Gliese 12 is about a quarter of the sun’s size, with about 60% of its surface temperature.
Dholakia co-led the team – with a University of Edinburgh PhD student, Larissa Palethorpe – who collaborated with Nasa to confirm the new planet.
“It’s only 40 light years away, and this might not mean that we can actually get to it any time in the near future, but it does mean that we can point the largest space telescopes in the world at it, and understand what its atmosphere might be like,” Dholakia said.
That could shed light on our own solar system.
“Earth and Venus are classic examples of how an atmosphere can change the surface of a planet. So Earth is this haven for life as we know it and Venus is hot enough to melt lead on its surface.
“And the difference between these two planets is largely because Venus has a very hostile atmosphere. So we think that this planet, which is right in between Earth and Venus in terms of the amount of light that it gets from its sun, could actually bridge the gap … and help us understand why Venus and Earth turned out to be so different.”
He said he mostly enjoyed the process although it was occasionally “intimidating”.
Nasa uses a transiting exoplanet survey satellite – Tess – to observe the brightness changes of tens of thousands of stars to capture “transits” – “brief, regular dimmings of stars caused by the passage of orbiting worlds”, according to its website.
It is easier to spot Earth-sized planets orbiting red dwarfs because, as a smaller star, the dimming of the transit is greater, and the lower mass means the orbiting planet produces a greater “wobble” or “reflex motion” in the star.
Nasa said Gliese 12b was a good candidate for further study using the James Webb space telescope.
A prominent US astronomer has said he is certain there’s a new planet lurking even closer to home. The ABC reported on Friday that a California Institute of Technology planetary astronomy professor, Michael Brown, said he did not see how we could have a solar system “without Planet Nine”.
For years he has said the peculiar paths of various objects around Neptune show the gravitational pull of another planet – but no one has been able to find it.
In a new study – not yet peer-reviewed – Brown and his team ran simulations and concluded there was a one-in-a-million chance that Planet Nine was not out there.
