西村彗星

西村彗星

ByNASA中文

2023年9月9日 Comet Nishimura Grows Credit & Copyright: Peter Kennett Explanation: Comet Nishimura is growing. More precisely, the tails C/2023 P1 (Nishimura) are growing as it nears the Sun. Discovered only last month, the comet is already near naked eye brightness as it now moves inside the Earth’s orbit. The comet will be nearest the Earth next week, but nearest the Sun the week after — on September 17. Speculation holds that expelled ice and dust from Comet Nishimura‘s last visit to the inner Solar System may have created the Sigma Hydrids meteor shower which peaks yearly in December. If so, then this meteor shower may become more active, refreshed with new comet debris. Pictured, Comet Nishimura was captured from Edgewood, New Mexico, USA four nights…

英仙座流星雨

英仙座流星雨

ByNASA中文

2023年8月9日 Meteor Shower: Perseids from Perseus Credit & Copyright: Petr Horálek / Institute of Physics in Opava Explanation: This is a good week to see meteors. Comet dust will rain down on planet Earth, streaking through dark skies during peak nights of the annual Perseid Meteor Shower. The featured composite image was taken during the 2018 Perseids from the Poloniny Dark Sky Park in Slovakia. The dome of the observatory in the foreground is on the grounds of Kolonica Observatory. Although the comet dust particles travel parallel to each other, the resulting shower meteors clearly seem to radiate from a single point on the sky in the eponymous constellation Perseus. The radiant effect is due to perspective, as the parallel tracks appear to converge at…

冰岛上空的流星和极光

冰岛上空的流星和极光

ByNASA中文

2021年12月13日 Meteors and Auroras over Iceland Image Credit & Copyright: James Boardman-Woodend; Annotation: Judy Schmidt Explanation: What’s going on behind that mountain? Quite a bit. First of all, the mountain itself, named Kirkjufell, is quite old and located in western Iceland near the town of Grundarfjörður. In front of the steeply-sloped structure lies a fjord that had just begun to freeze when the above image was taken — in mid-December of 2012. Although quite faint to the unaided eye, the beautiful colors of background aurorae became quite apparent on the 25-second exposure. What makes this image of particular note, though, is that it also captures streaks from the Geminids meteor shower — meteors that might not have been evident were the aurora much brighter. Far…

双子流星雨

双子流星雨

ByNASA中文

2021年11月16日 Geminids from Gemini Image Credit & Copyright: Wang Jin Explanation: Where are all of these meteors coming from? In terms of direction on the sky, the pointed answer is the constellation of Gemini. That is why the major meteor shower in December is known as the Geminids — because shower meteors all appear to come from a radiant toward Gemini. Three dimensionally, however, sand-sized debris expelled from the unusual asteroid 3200 Phaethon follows a well-defined orbit about our Sun, and the part of the orbit that approaches Earth is superposed in front of the constellation of Gemini. Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Gemini. Featured here, a composite of many images taken during the 2020 Geminids…

英仙座流星雨和失落的流星

英仙座流星雨和失落的流星

ByNASA中文

2021年8月9日 Perseus and the Lost Meteors Image Credit & Copyright: Tomas Slovinsky (Slovakia) & Petr Horalek (Czech Republic; Institute of Physics in Opava) Explanation: What’s the best way to watch a meteor shower? This question might come up later this week when the annual Perseid Meteor Shower peaks. One thing that is helpful is a dark sky, as demonstrated in the featured composite image of last year’s Perseids. Many more faint meteors are visible on the left image, taken through a very dark sky in Slovakia, than on the right image, taken through a moderately dark sky in the Czech Republic. The band of the Milky Way Galaxy bridges the two coordinated images, while the meteor shower radiant in the constellation of Perseus is clearly…

火流星的光与声

火流星的光与声

ByNASA中文

2021年03月15日 Meteor Fireballs in Light and Sound Image Credit & Copyright: Thomas Ashcraft (Radio Fireball Observatory) Explanation: Yes, but have you ever heard a meteor? Usually, meteors are too far away to make any audible sound. However, a meteor will briefly create an ionization trail that can reflect a distant radio signal. If the geometry is right, you may momentarily hear — through your radio — a distant radio station even over static. In the featured video, the sounds of distant radio transmitters were caught reflecting from large meteor trails by a sensitive radio receiver — at the same time the bright streaks were captured by an all-sky video camera. In the video, the bright paths taken by four fireballs across the sky near Lamy,…

远方的小行星

远方的小行星

ByNASA中文

2021年01月31日 Asteroids in the Distance Image Credit: NASA, ESA, Hubble; R. Evans & K. Stapelfeldt (JPL) Explanation: Rocks from space hit Earth every day. The larger the rock, though, the less often Earth is struck. Many kilograms of space dust pitter to Earth daily. Larger bits appear initially as a bright meteor. Baseball-sized rocks and ice-balls streak through our atmosphere daily, most evaporating quickly to nothing. Significant threats do exist for rocks near 100 meters in diameter, which strike the Earth roughly every 1000 years. An object this size could cause significant tsunamis were it to strike an ocean, potentially devastating even distant shores. A collision with a massive asteroid, over 1 km across, is more rare, occurring typically millions of years apart, but could…