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Astronomers have found an unusually large planet orbiting a small star about 280 light-years from Earth.
The unexpected size of the newly discovered world called TOI 5205b has prompted researchers to dub it the “forbidden planet”.
About the size of Jupiter, it was discovered by researchers using NASA’s Transiting Exoplanet Survey Satellite, or TESS. Jupiter is the largest planet in our solar system.
Launched in 2018, the planet-hunting mission examines the light from the nearest and brightest stars to detect dips in starlight, suggesting these stars have planets orbiting them. The TESS mission has found thousands of potential planets.
The exoplanet orbits a red dwarf star called TOI-5205, which is about 40% the size and mass of our Sun and has a temperature of about 5,660 degrees Fahrenheit (3,127 degrees Celsius), compared to the Sun’s blazing average of 9,980 F (5,527 C ). .
An M dwarf star is smaller, cooler, and redder than our Sun. These faint stars are among the most common in the Universe, and in recent years astronomers have discovered that M dwarf stars are more likely to have planets orbiting them.
But astronomers hadn’t counted on such small stars harboring giant planets – and that’s exactly what they found when they took a closer look at the planetary system TOI-5205.
A study detailed the results published Tuesday in the Astronomical Journal.
“The host star TOI-5205 is only about four times the size of Jupiter, but somehow managed to form a Jupiter-sized planet, which is quite surprising” said study author Shubham Kanodia, a postdoctoral researcher at the Carnegie Institution for Science in Washington, DC, in a statement.
Astronomers have found a few gas giant planets orbiting older M dwarf stars, but TOI 5205b is the first gas giant found around a low-mass M dwarf star.
The researchers likened the planet to a pea spinning around a lemon. In our solar system, Jupiter could be likened to a pea orbiting a grapefruit (representing our sun).
When TOI 5205b crosses in front of its star during orbit, the planet blocks 7% of its light.
The discovery of the planetary system challenges theories of planet formation.
Stars form from massive clouds of gas and dust in space. The leftover material from star formation swirls around the star, creating a rotating disc on which planets are born.
“The existence of TOI-5205b advances our knowledge of the discs in which these planets are born,” Kanodia said.
“Initially, if there isn’t enough rocky material in the disk to form the initial core, you can’t form a gas giant planet. And in the end, if the disk evaporates before the massive core has formed, then you can’t form a gas giant planet. And yet, despite these guardrails, TOI-5205b formed. Based on our nominal current understanding of planet formation, TOI-5205b should not exist; it is a ‘forbidden’ planet.”
Researchers want to observe the planet in the future with the James Webb Space Telescope, which could detect TOI-5205b has an atmosphere and unlock more mysteries about how it is educated.
Data collected by the Habitable Zone Planet Finder on the 10-meter Hobby Eberly Telescope at the University of Texas at Austin’s McDonald Observatory shows the potential for future discoveries, according to the research team.
Observations “already point to the presence of other such planets, suggesting that TOI-5205 b — while definitely an outlier — is not the only one,” Kanodia wrote in a blog post.
