TOI-257b is about 250 light years away and transits a bright white star every 18 days. It is likely a gaseous world, given its low density – with a mass 40 times that of Earth, but a volume almost 350 times greater than our planet.
MINERVA-Australis, an array of ﬁve 70-centimetre aperture robotic telescopes at the USQ-operated Mount Kent Observatory near Greenmount, supplies crucial support to NASA’s Transiting Exoplanet Survey Satellite (TESS).
Lead author, astrophysicist Dr Brett Addison, said the team followed up an initial detection of TOI-257b from TESS to confirm the exoplanet.
"This is a significant discovery, not just for USQ and Queensland, but as an example of cool and unusual planet types. TOI-257b is an example of what astronomers call ‘sub-Saturns’ (larger than Neptune and smaller than Saturn), a type of planet absent from the solar system," Dr Addison explained.
“The universe is a quirky and diverse place, with broad classes of planet such as sub-Saturns, super-Earths and mini Neptunes that we don’t have here at home. Warm sub-Saturns, like TOI-257b, are rare amongst the currently known exoplanets."
As the only dedicated ‘exoplanet hunting’ facility in the southern hemisphere, MINERVA-Australis has played a key role in the confirmation discovery of 19 exoplanets, but TOI-257b marks the first Australian-led confirmation of planet detected by TESS.
Addison added, "As of January, the TESS mission has delivered a total of 1,604 planetary candidates and follow-up observations have resulted in a total of 37 conﬁrmed planetary discoveries."
Some interesting facts about TOI-257b include:
- Like Saturn, the planet is less dense than water – it would float if we found an ocean large enough;
- Thinking of a holiday? Bring sunscreen – TOI-257b’s cloud tops reach at least 1,300 degees; and
- It may be a Queenslander, but forget calling it Planet Maroon. TOI-257b can only be officially named by the International Astronomical Union.
"It is likely that many more planets will be conﬁrmed in the months to come, and MINERVA-Australis will continue to play an important role. In fact, our data shows strong evidence for a second planet in the system, TOI-257c, which we hope to confirm in the coming year," Dr Addison explained.
MINERVA-Australis is funded by the Australian Research Council, USQ and international partners (Massachusetts Institute of Technology, George Mason University, University of Louisville, University of Florida, University of Texas, University of California, Riverside, and Nanjing University).
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