演講資訊

摘要：

On 10th April 2019, we, the Event Horizon Telescope Collaboration (EHTC), are pleased to present the image of the shadow of the supermassive black hole (SMBH) for the first time in human history. M87 was observed with the EHT on April 5, 6, 10 and 11, 2017 with 7 stations (ALMA, APEX, IRAM 30m, JCMT, LMT, SMA, SMT) located at 5 different sites on Earth. After a long process of careful data validation, calibration and many cross-checks by the EHTC, the final 1.3 mm VLBI image of M 87 reveals an asymmetric ring morphology of the central compact radio source with a diameter of 42±3 uas. The ring is almost circular and encompasses a central brightness depression of > 10:1. The robustness of this feature over multiple days strongly suggests that we see gravitationally lensed emission originating from near the black hole event horizon. The asymmetry is from Doppler beaming due to relativistic rotation in the emitting plasma. From the measured ring size, we derived a black hole mass of MBH=(6.5±0.7)×109 Msun. The image provides solid evidence for the presence of the SMBH at the center of M87 and supports the longstanding hypothesis that supermassive black holes power active galactic nuclei. Moreover, it demonstrates that millimeter VLBI offers a powerful method to explore gravity in its most extreme limit and at a previously inaccessible mass scale. I will summarize our discovery and state contribution of Taiwan.