New Delhi: Scientists from Ahmedabad’s Physical Research Laboratory (PRL) have discovered a dense Saturn-sized exoplanet orbiting a Sun-like star. It is five times larger and around 60 times heavier than the Earth.
Senior scientists at the PRL told ThePrint that the exoplanet, named TOI-6651b, was discovered using the PARAS-2 (PRL Advanced Radial-velocity All-sky Search-2) spectrograph and is the fourth exoplanet discovered by scientists from the institute.
PARAS-2 is a high-resolution spectrograph attached to the recently installed 2.5-metre telescope in the PRL’s Mount Abu InfraRed Observatory (MIRO).
“We have found that around 87 percent of the planet’s mass consists of dense materials such as rocks and iron in the core, and the remaining mass comprises a low-density envelope of hydrogen and helium,” a senior scientist from the PRL, who did not want to be named, explained.
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Significance of discovery
PRL scientists have said that the discovery of TOI-6651b is significant because it is located at the edge of a ‘Neptunian desert’ or ‘sub-Jovian desert—a region close to a star where usually no Neptune-sized exoplanets are found.
The discovery is also significant because it challenges conventional planet formation theories. The exoplanet may have been formed as a result of merging events or a significant atmospheric mass loss through tidal heating, which is the repeated deformation of a celestial body, say, a moon, due to tides in another body, say, a planet, resulting in the heating of the former’s interior.
Therefore, the discovery highlights the complex interplay of dynamic processes and atmospheric evolution in the formation of massive, dense sub-Saturn planets.
Researchers found that this distant planet takes 5.06 days to orbit its Sun-like host star. This means its ‘year’ equals less than a week on Earth. Its orbit is eccentric—slightly oval—which also distinguishes it from a planet.
The star, TOI-6651, is a G-type subgiant, which means it has used almost all of its hydrogen and is changing into a giant, a star that is not yet in the final stages of its life. A G-type subgiant has strong absorption lines from ionised calcium and appears yellow to the human eye.
The star is slightly larger and hotter than the Sun, with a surface temperature of about 5940 Kelvin. The discovery supports the theory of a positive correlation between planet mass and host star metallicity.
(Edited by Radifah Kabir)