関東上空に明るい「火球」　爆発音とどろく、通報も

　２日午前２時半ごろ、関東上空で非常に明るい流れ星「火球（かきゅう）」が目撃された。同時間帯には爆発したような音も聞かれ、ＳＮＳには「窓が揺れた」などの投稿が相次ぎ、警視庁には「爆発音が聞こえた」といった１１０番が東京都内各所から寄せられた。
　撮影した平塚市博物館（神奈川県）の藤井大地学芸員によると、火球は西から東へ移動し、満月よりも明るく感じたという。爆発音は衝撃波と考えられ、藤井氏は「非常に大きな流星の粒とみられ、地上に達して隕石（いんせき）になった可能性もある」と指摘した。
　国立天文台によると、流れ星でも特に明るいものを「火球」と呼ぶ。飛んできた塊が大きかったり、速度が速かったりすると通常より明るく輝く。音が聞こえることはまれだという。（2020/07/02-11:11）

A bolide, or a very bright meteor, was spotted in the sky over the Kanto region of eastern Japan around 2:30 a.m. Thursday (5:30 p.m. Wednesday GMT).
   Tokyo's Metropolitan Police Department received many emergency phone calls from residents reporting that they heard an explosive sound around the time, while a number of comments were posted on social media, including one saying that "windows were shaken."
   Daichi Fujii, a curator at the Hiratsuka City Museum in Kanagawa Prefecture, south of Tokyo, who filmed the fireball, said that the flying object traveled from west to east and was brighter than the full moon.
   The reported explosive sound is believed to have been created by a shock wave, Fujii said, adding that the fireball "was likely to be a fragment of a very large shooting star and may have made it to Earth's surface and become a meteorite."
   According to an official of the National Astronomical Observatory of Japan, a bolide shines very brightly if it is big or travels fast. It is rare for a sound from a bolide to be heard, the official said.