‘Missing link’ worlds discovered

By on 30 July, 2019

Artist’s impression of Transiting Exoplanet Survey Satellite (TESS). Image: NASA.

NASA’s planet-hunting TESS satellite has discovered three new worlds orbiting a neighbouring star.

The planetary system, TESS Object of Interest 270 (TOI-270), is in the constellation of Pictor, around 73 light years from Earth.

Two of the newly-found planets are of a gaseous type not found in our own solar system, roughly twice Earth’s size, and one is rocky and slightly larger than Earth — and in the habitable zone, meaning that it is warm enough to allow for liquid oceans.

The sun to these new planets is a faint, cool M-type dwarf star known by its catalogue name, UCAC4 191-004642. It is around 40 percent smaller than our sun in size and mass, with a surface temperature around one-third cooler.

Infographic: NASA.

TOI 270 b is the innermost planet, likely around 25 percent Earth’s side and of rocky composition, orbiting the star every 3.4 days at a distance 13 times closer than Mercury is to our sun. Its equilibrium temperature, which is calculated from the energy it receives from the star and does not account for warming effects, is around 254 degrees Celsius.

TOI 270 d and c are around 2.4 and 2.1 times larger than Earth, orbiting the star every 5.7 and 11.4 days respectively. All three planets are anticipated to be tidally locked — meaning that they only rotate once per orbit and keep the same side facing the star all times.

Our solar system is composed of small, rocky planets like Earth, Mars, Venus and Mercury, or much larger gaseous planets like Jupiter, Saturn and Uranus — but no planets around half Neptune’s size.

Click to enlarge. Infographic: NASA.

“TOI-270 will soon allow us to study this ‘missing link’ between rocky Earth-like planets and gas-dominant mini-Neptunes, because here all of these types formed in the same system,” said lead researcher Maximilian Gunther, a Torres Postdoctoral Fellow at the Massachusetts Institute of Technology.

The team hopes that further study may reveal planets as-of-yet undiscovered in the TOI 270 system.

“TOI 270 is perfectly situated in the sky for studying the atmospheres of its outer planets with NASA’s future James Webb Space Telescope,” said co-author Adina Feinstein, a doctoral student at the University of Chicago. “It will be observable by Webb for over half a year, which could allow for really interesting comparison studies between the atmospheres of TOI 270 c and d.”

The results of the discovery were published in Nature Astronomy.

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