https://blog.wongcw.com/2021/06/10/%e5%a4%a9%e6%96%87%e5%ad%b8%e5%ae%b6%e7%99%bc%e7%8f%be%e8%b6%85%e5%a4%a7%e8%b3%aa%e9%87%8f%e9%bb%91%e6%b4%9e%e7%9a%84%e5%9e%82%e6%ad%bb%e8%bf%b4%e8%81%b2/
天文學家發現超大質量黑洞的“垂死迴聲”