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Abstract A recent study by Hon et al. reported that a close-in planet around the red clump star, 8 UMi, should have been engulfed during the expansion phase of its parent star’s evolution. They explained the survival of this exoplanet through a binary-merger channel for 8 UMi. The key to testing this formation scenario is to derive the true age of this star: is it an old “imposter” resulting from a binary merger, or a genuinely young red clump giant? To accomplish this, we derive kinematic and chemical properties for 8 UMi using astrometric data from Gaia DR3 and the element-abundance pattern measured from a high-resolution (R∼ 75,000) spectrum taken by SOPHIE. Our analysis shows that 8 UMi is a normal thin-disk star with orbital rotation speed ofV_ϕ= 244.96 km s⁻¹, and possesses a solar metallicity ([Fe/H] = −0.05 ± 0.07) andα-element-abundance ratio ([α/Fe] = +0.01 ± 0.03). By adopting well-established relationships between age and space velocities/elemental abundances, we estimate a kinematic age of ${3.50}_{-2.00}^{+3.00}$Gyr, and a chemical age of ${3.25}_{-1.50}^{+2.50}$Gyr from [C/N] and 3.47 ± 1.96 Gyr from [Y/Mg] for 8 UMi, respectively. These estimates are consistent with the isochrone-fitting age ( ${1.90}_{-0.30}^{+1.15}$Gyr) of 8 UMi, but are all much younger than the timescale required in a binary-merger scenario. This result challenges the binary-merger model; the existence of such a closely orbiting exoplanet around a giant star remains a mystery yet to be resolved. 

Abstract During October 2019 and March 2020, the luminous red supergiant Betelgeuse demonstrated an unusually deep minimum of its brightness. It became fainter by more than one magnitude and this is the most significant dimming observed in the recent decades. While the reason for the dimming is debated, pre-phase of supernova explosion, obscuring dust, or changes in the photosphere of the star were suggested scenarios. Here, we present spectroscopic studies of Betelgeuse using high-resolution and high signal-to-noise ratio near-infrared spectra obtained at Weihai Observatory on four epochs in 2020 covering the phases of during and after dimming. We show that the dimming episode is caused by the dropping of its effective temperature by at least 170 K on 2020 January 31, that can be attributed to the emergence of a large dark spot on the surface of the star.