2023年08月21日:西村彗星-（Introducing Comet Nishimura） 2023年08月21日:西村彗星-（Introducing Comet Nishimura）--原图下载{mtitle title="西村彗星"/}Credit & Copyright: Dan Bartlett说明: 西村彗星会亮到肉眼可见吗？鑒于彗星的不可预测性，没人能说个准，但目前这种可能性颇高。这颗彗星是西村荣男刚在十天前，用标准数码相机进行30秒长曝光时所发现的。从那时起，西村彗星（C/2023 P1 Nishimura）的亮度持续增加，而穿过太阳系内围的路径也获得确定。随着这颗彗星向太阳俯冲，它肯定会继续增亮，并可能在9月初成为一个肉眼可见的天体。问题是：届时这颗彗星的视角也会和太阳很接近，所以只能在日落或日出前后见到它。这颗彗星将会进到水星轨道之内，离太阳非常近，以至于它的彗核或许会崩解。上图所呈现的是3天前摄于美国．加州．六月湖的西村彗星，当时它曳着泛绿的彗发和和纤细的彗尾。（Comet Nishimura 西村彗星）{lamp/}原文：{mtitle title="Introducing Comet Nishimura"/}Credit & Copyright: Dan BartlettExplanation: Will Comet Nishimura become visible to the unaided eye?Given the unpredictability of comets, no one can say for sure, but it currently seems like a good bet. The comet was discovered only ten days ago by Hideo Nishimura during 30-second exposures with a standard digital camera. Since then, C/2023 P1 Nishimura has increased in brightness and its path across the inner Solar System determined. As the comet dives toward the Sun, it will surely continue to intensify and possibly become a naked-eye object in early September. A problem is that the comet will also be angularly near the Sun, so it will only be possible to see it near sunset or sunrise. The comet will get so close to the Sun -- inside the orbit of planet Mercury -- that its nucleus may break up.Pictured, Comet Nishimura was imaged three days ago from June Lake, California, USA while sporting a green coma and a thin tail.

2023年06月30日:可能会祸害地球的小行星之轨道-（Orbits of Potentially Hazardous Asteroids） 2023年06月30日:可能会祸害地球的小行星之轨道-（Orbits of Potentially Hazardous Asteroids）--原图下载{mtitle title="可能会祸害地球的小行星之轨道"/}Illustration Credit: NASA, JPL-Caltech说明: 小行星会造成祸害吗？ 有些会，但一颗具危险性小行星在某特定年会撞击地球的可能性则很低。在过往，小行星撞击曾导致生物大灭绝事件，是以人类把寻找和编录未来可能会祸害地球上生物的小行星之工作列为优先。上图 呈现了超过1,000颗可能具有危害性的小行星 (PHAs)之轨道。这些已登录、在太空翻滚的巨石或冰块，大小超过140公尺，而其通过地球时的间距小于7百50万公里，大约是月球距离的20倍。虽然这些小行星在未来的百年之中，都不会撞击地球，但并非所有具危害性的小行星都已找到，而且一百年后有些小行星的轨道难以预测。如果上述这种寛140公尺的小行星之一冲撞地球，灾害之一是会引发危险的海啸。为了探索救助地球的策略，美国航太总署已在去年成功执行了双小行星改道测试任务（DART）。 事实上，每天都有许多的细小的石块和冰块撞击地球，但它们通常不会带来危害，偶而甚至会形成令人难忘的火流星或流星雨。{lamp/}原文：{mtitle title="Orbits of Potentially Hazardous Asteroids"/}Illustration Credit: NASA, JPL-CaltechExplanation: Are asteroids dangerous?Some are, but the likelihood of a dangerous asteroid striking the Earth during any given year is low.Because some past mass extinction events have been linked to asteroid impacts, however, humanity has made it a priority to find and catalog those asteroids that may one day affect life on Earth.Pictured here are the orbits of the over 1,000 known Potentially Hazardous Asteroids (PHAs).These documented tumbling boulders of rock and ice are over 140 meters across and will pass within 7.5 million kilometers of Earth -- about 20 times the distance to the Moon.Although none of them will strike the Earth in the next 100 years -- not all PHAs have been discovered, and past 100 years, many orbits become hard to predict.Were an asteroid of this size to impact the Earth, it could raise dangerous tsunamis, for example.To investigate Earth-saving strategies, NASA successfully tested the Double Asteroid Redirection Test (DART) mission last year.Of course, rocks and ice bits of much smaller size strike the Earth every day, usually pose no danger, and sometimes create memorable fireball and meteor displays.

2021年08月29日:可能会危害地球的小行星之轨道-（Orbits of Potentially Hazardous Asteroids） 2021年08月29日:可能会危害地球的小行星之轨道-（Orbits of Potentially Hazardous Asteroids）--原图下载{mtitle title="可能会危害地球的小行星之轨道"/}Image Credit: NASA, JPL-Caltech说明: 小行星会造成危害吗？有些会，但一颗危险小行星在特定年会撞击地球的可能性则很低。在过往，小行星撞击曾导致生物大灭绝事件，所以，人类把寻找和编录未来可能会危害地球生命的小行星之工作列为优先。上图呈现了超过1,000颗可能有危害性小行星 (PHAs)的轨道。这些已登录、在太空翻滚的巨石或冰块，大小超过140公尺，而通过地球时的间距小于7百50万公里，大约是月球距离的20倍。虽然这些小行星在未来百年之中，都不会冲撞地球，但并非所有危害性小行星都已找到，而且一百年后有些小行星的轨道难以预测。如果上述这种寛140公尺的小行星之一冲撞地球，危害之一是会引起危险的海啸。为探索救护地球的策略，美国航太总署规画在今年底进行双小行星改向测试（DART）任务。事实上，每天都有许多的细小的石块和冰块撞击地球，通常它们不会带来危害，偶而会形成火流星或流星雨。{lamp/}原文：{mtitle title="Orbits of Potentially Hazardous Asteroids"/}Image Credit: NASA, JPL-CaltechExplanation: Are asteroids dangerous?Some are, but the likelihood of a dangerous asteroid striking the Earth during any given year is low.Because some past mass extinction events have been linked to asteroid impacts, however, humanity has made it a priority to find and catalog those asteroids that may one day affect life on Earth.Pictured here are the orbits of the over 1,000 known Potentially Hazardous Asteroids (PHAs).These documented tumbling boulders of rock and ice are over 140 meters across and will pass within 7.5 million kilometers of Earth -- about 20 times the distance to the Moon.Although none of them will strike the Earth in the next 100 years -- not all PHAs have been discovered, and past 100 years, many orbits become hard to predict.Were an asteroid of this size to impact the Earth, it could raise dangerous tsunamis, for example.To investigate Earth-saving strategies, NASA's Double Asteroid Redirection Test (DART) is planned for launch later this year.Of course rocks and ice bits of much smaller size strike the Earth every day, usually pose no danger, and sometimes creating memorable fireball and meteor displays.

2021年04月13日:缈子确定有仍然无法解释的晃动-（Confirmed Muon Wobble Remains Unexplained） 2021年04月13日:缈子确定有仍然无法解释的晃动-（Confirmed Muon Wobble Remains Unexplained）--原图下载{mtitle title="缈子确定有仍然无法解释的晃动"/}Image Credit: Fermi National Accelerator Laboratory; Photographer: Reidar Hahn说明: 基本粒子能晃动多快呢？这个看似不搭调问题的意外解答，是在2001年由美国．纽约州的布鲁克黑文国家实验室所提出。这项结果指出：广为接受的粒子物理标准模型并不完整，也暗示宇宙还有待发现的基本组成。更具体的说，自从1999年进行了一序列称为g-2（g负2）的实验，以量测性质类似电子但质量较大的缈子，结果发现它有大于预期的晃动。这项在布鲁克黑文国家实验室获得的成果，激发世界各地的团队进行确认实验，并让理论学家致力于了解这项结果。上星期，在美国．伊利诺州的费米国家实验室（参见上图）进行，截自目前最灵敏精密的缈子晃动实验，发布与布鲁克黑文实验室一致的成果，亦即缈子具有超量的异常晃动。缈子的晃动率，与奇异虚粒子海里大量随机生成湮没的粒子紧密相关。缈子异常的晃动率，或许暗示这片粒子海里，有超出标准模型的虚粒子。或者这项结果暗示，使用超级电脑及极端複杂程式进行的理论预测有缺陷。后续在费米实验室进行的g-2实验，将致力于提升精密度，可能的话并找出我们了解的与量测的宇宙，二者之间的统计学差异。（muon wobble 缈子晃动）{lamp/}原文：{mtitle title="Confirmed Muon Wobble Remains Unexplained"/}Image Credit: Fermi National Accelerator Laboratory; Photographer: Reidar HahnExplanation: How fast do elementary particles wobble? A surprising answer to this seemingly inconsequential question came out of Brookhaven National Laboratory in New York, USA in 2001, and indicated that the Standard Model of Particle Physics, adopted widely in physics,is incomplete.Specifically, the muon, a particle with similarities to a heavy electron, has had its relatively large wobble under scrutiny in a series of experiments known as g-2 (gee-minus-two).The Brookhaven result galvanized other experimental groups around the world to confirm it, and pressured theorists to better understand it. Reporting in last week, the most sensitive muon wobble experiment yet, conducted at Fermi National Accelerator Laboratory (Fermilab) in Illinois and pictured here, agreed with the Brookhaven result.The unexpected wobble rate may indicate that an ever-present sea of virtual particles includes types not currently known. Alternatively, it may indicate that flaws exist in difficult theoretical prediction calculations.Future runs at Fermilab's g-2 experiment will further increase precision and, possibly, the statistical difference between the universe we measure and the universe we understand.

2020年09月20日:解析遥远的星光-（Breaking Distant Light） 2020年09月20日:解析遥远的星光-（Breaking Distant Light）--原图下载{mtitle title="解析遥远的星光"/}Image Credit: VIMOS, VLT, ESO说明: 在遥远宇宙的那端，时间似乎流逝的较缓慢。由于时间膨胀之故，其星光会往光谱的红端偏移而产生红移的现象，天文学家们就可以用宇宙论时间膨胀的概念，来量测宇宙浩瀚的距离。在上图中，来自遥远星系的星光，已被分解它们的组成颜色 (亦即光谱)，让天文学家能用已知的光谱线去量测其宇宙红移。此图的创新之处在于使用 位在智利的 极大望远镜阵列之多目标可见光光谱仪，只要取得单张影像，就可以同时量测这数百个星系的距离。分析遥远天体的空间分布，可以帮助我们深入研究在宇宙初期，恒星、星系、类星体何时以及如何形成、聚集成团与演化。{lamp/}原文：{mtitle title="Breaking Distant Light"/}Image Credit: VIMOS, VLT, ESOExplanation: In the distant universe, time appears to run slowly. Since time-dilated light appears shifted toward the red end of the spectrum (redshifted), astronomers are able to use cosmological time-slowing to help measure vastdistances in the universe. Featured, the light from distant galaxies has been broken up into its constituent colors (spectra), allowing astronomers to measure the cosmological redshift of known spectral lines. The novelty of the featured image is that the distance to hundreds of galaxies can be measured from a single frame, in this case one taken by the Visible MultiObject Spectrograph (VIMOS) operating at the Very Large Telescope (VLT) array in Chile. Analyzing the space distribution of distant objects will allow insight into when and how stars and galaxies formed, clustered, and evolved in the earlyuniverse.

2020年08月02日:二个世界、一个太阳-（Two Worlds, One Sun） 2020年08月02日:二个世界、一个太阳-（Two Worlds, One Sun）--原图下载{mtitle title="二个世界、一个太阳"/}Left Image Credit & Copyright: Damia Bouic; Right Image Credit: NASA,JPL-Caltech,MSSS; Digital processing: Damia Bouic说明: 火星与地球的日落有多大的差异？为了进行比较，上图呈现了二幅分别摄于地球和火星的日落景观。这些影像的大小经过缩放，以保证它们具有相同的视张角，以便于并排比较。乍看之下可发现，从火星看出去，太阳貌似比在地球所见的要小一些；这项特色很合理，因为火星和太阳的间距要比地球大上50%。影像最明显的差异是：火星落日的色泽，要比地球常见的橘红色落日要更蓝一些。为何火星落日较蓝，其成因并不全然清楚，咸认是和火星尘埃的前向散射性质有所关联。的前向散射性质有所关联。这幅地球落日照摄于2012年3月的法国．马赛，而火星落日则是在2015年由美国航太总署的好奇号火星车，摄于火星的盖尔坑之内。在上星期发射的2020火星任务，正把一部全新的火星车和直升机送往火星。{lamp/}原文：{mtitle title="Two Worlds, One Sun"/}Left Image Credit & Copyright: Damia Bouic; Right Image Credit: NASA,JPL-Caltech,MSSS; Digital processing: Damia BouicExplanation: How different does sunset appear from Mars than from Earth?For comparison, two images of our common star were taken at sunset, one from Earth and one from Mars.These images were scaled to have same angular width and featured here side-by-side.A quick inspection will reveal that the Sun appears slightly smaller from Mars than from Earth.This makes sense since Mars is 50% further from the Sun than Earth.More striking, perhaps, is that the Martian sunset is noticeably bluer near the Sun than the typically orange colors near the setting Sun from Earth.The reason for the blue hues from Mars is not fully understood, but thought to be related to forward scattering properties of Martian dust.The terrestrial sunset was taken in 2012 March from Marseille, France, while the Martian sunset was captured in 2015 by NASA's robotic Curiosity rover from Gale crater on Mars.Last week a new rover and a helicopter -- onboard Mars 2020 -- launched for Mars.