by In an exciting discovery, astronomers using NASA’s Transiting Exoplanet Survey Satellite (TESS) have found two new hot Jupiter exoplanets. Known as TOI-4377 b and TOI-4551 b, these alien worlds orbit distant red-giant stars. The finding was recently published in the Monthly Notices of the Royal Astronomical Society.
Launched in April 2018, TESS is on a mission to survey approximately 200,000 of the brightest stars near the sun in search of transiting exoplanets, ranging from small rocky worlds to gaseous giants. To date, TESS has identified nearly 7,000 potential exoplanets, with 402 of them confirmed so far.
Led by Filipe Pereira from the University of Porto, Portugal, a group of astronomers has now confirmed two more TESS Objects of Interest (TOI) – TOI-4377 and TOI-4551. They detected a transit signal in the light curves of these red-giant stars, which are located 1,486 and 704 light years away. The team verified the planetary nature of these signals through follow-up radial velocity observations using ground-based telescopes.
The researchers explained in their paper that the planets were found during a search for transits around bright low-luminosity red-giant branch stars observed by TESS in the southern ecliptic hemisphere.
TOI-4377 b is approximately 1.35 times the size of Jupiter and has a mass of around 0.96 times that of Jupiter. Its density is estimated to be 0.88 g/cm³. The planet orbits its host every 4.38 days at a distance of 0.058 astronomical units (AU). Its equilibrium temperature is yet to be determined.
On the other hand, TOI-4551 b has a radius about 6% larger than Jupiter and a mass estimated to be 1.49 times that of Jupiter. As a result, the planet has a density of 1.74 g/cm³. It has an orbital period of approximately 10 days and orbits its parent star at a distance of 0.1 AU.
Both TOI-4377 and TOI-4551 have masses of around 1.36 and 1.31 solar masses, respectively. These stars are approximately 3.5 times larger than the sun and have effective temperatures close to 5,000 K. TOI-4377 is estimated to be around 3.88 billion years old, while TOI-4551 is approximately 1 billion years older.
In conclusion, the researchers classified TOI-4377 b and TOI-4551 b as hot Jupiters and described them as rare examples of giant alien planets with short orbital periods, orbiting red-giant stars. Hot Jupiters are similar to Jupiter in characteristics and have orbital periods of less than 10 days. These exoplanets have high surface temperatures due to their close proximity to their parent stars.
Overall, the discovery of these two hot Jupiter exoplanets adds to our understanding of exoplanets orbiting evolved host stars. They are particularly significant for demographic studies of short-period giant planets around red-giant stars, where only a few planets have been identified so far, the researchers noted.
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