Exoplanet Mystery –”The Gas Giant That Should Not Exist”

Exoplanet YSES 2b


An exoplanet mystery has been imaged by a team of astronomers led by Dutch scientists of a giant planet orbiting at a large distance around a sun-like star.  The planet in question is YSES 2b, located 360 light years from Earth in the direction of the southern constellation of Musca (Latin for The Fly). 

Six Times Heavier than Jupiter

The gas giant planet is six times heavier than Jupiter, the largest planet in our solar system. The newly discovered planet orbits 110 times more distant from its star than the Earth does from the sun (or 20 times the distance between the sun and Jupiter). The star is only 14 million years old and resembles our sun in its childhood.

The image of YSES 2b (bottom right) and its star (center) is shown above. The star is not seen in the image as its light is blocked by a device called a coronagraph, thereby revealing faint objects in its immediate vicinity. Credit: ESO/SPHERE/VLT/Bohn et al.

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It’s Existence a Puzzle with No Solution –Except for One

The large distance from the planet to the star presents a puzzle to astronomers because it does not seem to fit either of the two most well-known models for the formation of large gaseous planets. If the planet had grown in its current location far from the star by means of core accretion, it would be too heavy because there is not enough material to make a huge planet at this large distance from the star. If the planet was created by so-called gravitational instability in the planetary disk, it appears to be not heavy enough. A third possibility is that the planet formed close to the star by core accretion and then migrated outwards. Such a migration, however, would require the gravitational influence of a second planet, which the researchers have not yet found.

Missed the Existence of an Inner Planet?

“From the current data it is really hard to pin down the most likely formation channel of YSES 2b,” wrote Lead researcher Alexander Bohn (Leiden University) in an email to The Daily Galaxy. ”It is certainly possible that we have missed an inner planet that is just below the sensitivity of our images. We hope to acquire more data on the system in the next year to test the hypothesis of a second, closer companion to the star that might have scattered YSES 2b to its current position.”

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The astronomers will continue to investigate the surroundings of this unusual planet and its star in the near future and hope to learn more about the system, and they will continue to search for other gaseous planets around young, sun-like stars. Current telescopes are not yet large enough to carry out direct imaging of Earth-like planets around sun-like stars, since such planets are small and faint.

“By investigating more Jupiter-like exoplanets in the near future, we will learn more about the formation processes of gas giants around sun-like stars,” said Bohn.

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The planet YSES 2b was discovered with the Young Ssuns Exoplanet Survey (YSES). This survey already provided the first direct image of a multi-planet system around a sun-like star in 2020. The researchers made their observations in 2018 and 2020 using the Very Large Telescope of the European Southern Observatory (ESO) in Chile. They used the telescope’s SPHERE instrument for those observations. This instrument was co-developed by the Netherlands and can capture direct and indirect light from exoplanets.

Source: Discovery of a directly imaged planet to the young solar analog YSES 2. By: Alexander J. Bohn et al. Accepted for publication in Astronomy & Astrophysics.

Avi Shporer, Research Scientist, MIT Kavli Institute for Astrophysics and Space Research, via University of Leiden.




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