TOI-712: A System of Adolescent Mini-Neptunes Extending to the Habitable Zone

As an all-sky survey, NASA's $TESS$ mission is able to detect the brightest and rarest types of transiting planetary systems, including young planets that enable study evolutionary processes occur within first billion years. Here, we report discovery a young, multi-planet system orbiting bright K4.5V star, TOI-712 ($V = 10.838$, $M_\star 0.733_{-0.025}^{+0.026} M_\odot$, $R_\star 0.674\pm0.016 R_\odot$, $T_{\rm eff} 4622_{-60}^{+61}$ K). From light curve, measure rotation period 12.48 days, derive age between about $500$ Myr 1.1 Gyr. The photometric observations reveal three mini-Neptunes ($R_b 2.049^{+0.12}_{-0.080} R_\oplus$, $R_c 2.701^{+0.092}_{-0.082} $R_d 2.474^{+0.090}_{-0.082} R_\oplus $), with orbital periods $P_b 9.531$ $P_c 51.699$ $P_d 84.839$ days. After modeling three-planet system, additional Earth-sized candidate identified, TOI-712.05 ($P 4.32$ $R_P 0.81 \pm 0.11 R_\oplus$). We calculate habitable zone falls 0.339 0.844 au (82.7 325.3 days), placing d near its inner edge. Among systems harboring temperate planets, ($T 9.9$) stands out as relatively star enough motivate further characterization.