在地球影子的边缘

在地球影子的边缘

2021年11月25日 At the Shadow’s Edge Image Credit & Copyright: Jean-Francois Gout Explanation: Shaped like a cone tapering into space, the Earth’s dark central shadow or umbra has a circular cross-section. It’s wider than the Moon at the distance of the Moon’s orbit though. But during the lunar eclipse of November 18/19, part of the Moon remained just outside the umbral shadow. The successive pictures in this composite of 5 images from that almost total lunar eclipse were taken over a period of about 1.5 hours. The series is aligned to trace part of the cross-section’s circular arc, with the central image at maximum eclipse. It shows a bright, thin sliver of the lunar disk still beyond the shadow’s curved edge. Of course, even within the…

哈勃见证了奔跑者星云中气体碰撞的冲击波

哈勃见证了奔跑者星云中气体碰撞的冲击波

Mounded, luminous clouds of gas and dust glow in this Hubble image of a Herbig-Haro object known as HH 45. Herbig-Haro objects are a rarely seen type of nebula that occurs when hot gas ejected by a newborn star collides with the gas and dust around it at hundreds of miles per second, creating bright shock waves. In this image, blue indicates ionized oxygen (O II) and purple shows ionized magnesium (Mg II). Researchers were particularly interested in these elements because they can be used to identify shocks and ionization fronts. 在这张哈勃拍摄的名为HH 45的赫比格-哈罗天体图像中,堆积的、发光的气体和尘埃云闪闪发光。赫比格-哈罗天体是一种罕见的星云,当新生恒星喷出的热气体以每秒数百英里的速度与周围的气体和尘埃碰撞,产生明亮的冲击波。在这张图片中,蓝色表示电离的氧(O II),紫色表示电离的镁(Mg II)。研究人员对这些元素特别感兴趣,因为它们可以用来识别冲击波和电离锋线。 This object is located in the nebula NGC 1977, which itself is part of a complex of three nebulae called The Running Man. NGC 1977 – like its companions NGC…

NASA、SpaceX发射DART:首次保卫地球的测试任务

NASA、SpaceX发射DART:首次保卫地球的测试任务

影像来源:NASA 美国东部时间周三凌晨1点21分,NASA的双小行星重定向测试(DART)由SpaceX猎鹰9号火箭在加利福尼亚州范登堡太空基地东四号航天发射中心发射,这是世界上首个全面测试保护地球免受小行星或彗星威胁技术的任务。 DART只是NASA更大的行星防御战略的一部分,它由位于马里兰州劳雷尔的约翰霍普金斯应用物理实验室(APL)建造和管理,DART将撞击一颗对地球没有威胁的已知小行星。它的目标是稍微改变该小行星的运动,其方式可以用地面望远镜准确测量。 DART将展示航天器可以自主导航到目标小行星并有意与其发生碰撞——一种称为动能撞击的偏转方法。该测试将提供重要数据,帮助更好地为可能对地球构成冲击危险的小行星做好准备。LICIACube是一颗由意大利航天局(ASI)提供的立方体卫星,与DART一起运行,将在DART撞击前发射,以捕捉撞击和由此产生的喷射物质云的图像。 在DART撞击大约四年后,欧洲航天局的Hera项目将对这两颗小行星进行详细的调查,特别关注DART撞击留下的陨石坑,并精确确定小行星Dimorphos的质量。 “DART正在把科幻小说变成科学事实,它证明了NASA为所有人的利益而进行的积极主动和创新。”NASA局长比尔·纳尔逊说。“除了NASA研究我们的宇宙和我们的地球的所有方法外,我们还致力于保护我们的家园,而这项测试将有助于证明一种可行的方法,如果发现有一颗危险的小行星朝向地球,可以保护我们的地球免受其害。” 凌晨2点17分,DART与火箭的二级分离。几分钟后,任务操作人员收到了第一个航天器遥测数据,并开始将航天器定向到一个安全的位置,以部署其太阳能电池阵列。大约两小时后,航天器成功地展开了它的两个28英尺长的太阳能电池阵列。它们将为航天器和NASA的进化型氙气推进器——商用离子发动机提供动力,这是正在DART上测试的若干技术之一,以便将来应用于太空任务。 “DART的核心是一项准备任务,它也是一项团结的任务。”位于华盛顿的NASA总部科学任务局副局长托马斯·左布臣说。“这项国际合作涉及DART、ASI的LICIACube、ESA的Hera调查和科学团队,它们将对这项开创性的太空任务采取后续行动。” DART的单程旅行是前往Didymos小行星系统,该系统包括一对小行星。DART的目标是小卫星Dimorphos,它的直径约为530英尺(160米)。这颗小卫星围绕着直径约为2560英尺(780米)的Didymos运行。 由于Dimorphos围绕Didymos运行的相对速度要比这对绕太阳运行的行星慢得多,因此在双星系统中DART的动力学影响比单个小行星围绕太阳运行轨道的变化更容易测量。 “我们还没有发现任何重大的小行星撞击地球的威胁,但我们继续寻找我们知道仍有相当大的群体有待发现。我们的目标是提前数年至数十年发现任何可能的撞击,这样就可以利用我们目前拥有的技术,像DART那样的能力来使它偏移。”NASA总部的行星防御官员林德利·约翰逊说。“DART是NASA工作的一个方面,目的是让地球做好准备,以防我们遇到小行星灾害。与此同时,我们正在准备近地物体测量任务,这是一个基于太空的红外望远镜,计划在本十年晚些时候发射,旨在加快我们发现和描述距离地球轨道3000万英里以内的潜在危险小行星和彗星的能力。” 该航天器将在2022年9月26日至10月1日之间拦截Didymos系统,故意以大约每秒4英里(每秒6公里)的速度撞向Dimorphos。科学家们估计,这种动力撞击将使Dimorphos围绕Didymos的轨道缩短几分钟。研究人员将使用地球上的望远镜精确测量这一变化。他们的结果将验证和改进科学的计算机模型,这些模型对于预测作为小行星偏转可靠方法的动力撞击的有效性至关重要。 “看到你在‘纸上的文字’阶段成为现实并发射到太空后所参与的事情,这是一种难以形容的感觉。”安迪·程说,他是约翰霍普金斯大学APL的DART调查负责人之一,也是提出DART想法的人。“这仅仅是第一幕的结束,DART的调查和工程团队在接下来的一年里还有很多工作要做,为主要的事件──DART对双态生物的动力学影响做准备。但今晚我们要庆祝!” DART的唯一仪器,Didymos侦察和小行星光学导航相机(DRACO),将在一周后启用,并提供航天器的第一批图像。DART在未来10个月内将继续在地球绕太阳运行的轨道之外运行,直到Didymos和Dimorphos离地球的距离为680万英里(1100万公里)。 一个复杂的制导、导航和控制系统,与称为小体机动自主实时导航(SMART Nav)的算法一起工作,将使DART航天器能够识别和区分这两颗小行星。然后,该系统会将航天器引导至 Dimorphos。这一过程将在撞击前大约一小时内发生。 约翰霍普金斯APL管理NASA行星防御协调办公室的DART任务,作为该机构行星任务计划办公室的一个项目。 NASA为该任务提供了多个中心的支持,包括南加州的喷气推进实验室、马里兰州格林贝尔特的戈达德太空飞行中心、休斯顿的约翰逊航天中心、克利夫兰的格伦研究中心和弗吉尼亚州汉普顿的兰利研究中心。此次发射由NASA的发射服务项目管理,该项目位于该机构位于佛罗里达州的肯尼迪航天中心。SpaceX是DART任务的发射服务提供商。 有关DART任务的更多信息,请访问: https://www.nasa.gov/dartmission 参考来源: https://www.nasa.gov/press-release/nasa-spacex-launch-dart-first-test-mission-to-defend-planet-earth

昴宿星团:七姐妹星团

昴宿星团:七姐妹星团

2021年11月24日 Pleiades: The Seven Sisters Star Cluster Image Credit & Copyright: Damien Cannane Explanation: Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as large and clear as this. Perhaps the most famous star cluster on the sky, the bright stars of the Pleiades can be seen without binoculars from even the depths of a light-polluted city. With a long exposure from a dark location, though, the dust cloud surrounding the Pleiades star cluster becomes very evident. The featured exposure, taken from Florida, USA, covers a sky area several times the size of the full moon. Also known as the Seven Sisters and M45, the Pleiades lies about 400 light years away toward the constellation of…

敬请关注DART!

敬请关注DART!

The Double Asteroid Redirection Test (DART), which will help determine if intentionally crashing a spacecraft into an asteroid is an effective way to change its course, is scheduled to launch no earlier than 1:21 a.m. EST Wednesday, Nov. 24 (10:21 p.m. PST Tuesday, Nov. 23) on a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California. 双重小行星重定向测试(DART)将有助于确定故意将航天器撞向小行星是否是改变其轨道的有效方式,该测试计划不早于美国东部时间11月24日星期三凌晨1:21(北京时间11月23日星期二晚上10:21),由SpaceX猎鹰9号火箭从加利福尼亚州范登堡空军基地发射。 This illustration is of the DART spacecraft and the Italian Space Agency’s (ASI) LICIACube prior to impact at the Didymos binary system. 这张插图是DART航天器和意大利航天局(ASI)的LICIACube在撞击Didymos双星系统之前的示意图。 DART is the agency’s first planetary defense test mission and the target asteroid is not a threat to Earth. DART是NASA的第一个行星防御测试任务,目标小行星对地球不构成威胁。 Learn more about social media and other activities for the mission. 了解更多关于该任务的社交媒体和其他活动。 Image Credits: NASA/Johns Hopkins, APL/Steve Gribben 图片来源: NASA/Johns Hopkins, APL/Steve Gribben

核分光望远镜拍摄的X波段太阳

核分光望远镜拍摄的X波段太阳

2021年11月23日 The Sun in X-rays from NuSTAR Image Credit: NASA, NuSTAR, SDO Explanation: Why are the regions above sunspots so hot? Sunspots themselves are a bit cooler than the surrounding solar surface because the magnetic fields that create them reduce convective heating. It is therefore unusual that regions overhead — even much higher up in the Sun’s corona — can be hundreds of times hotter. To help find the cause, NASA directed the Earth-orbiting Nuclear Spectroscopic Telescope Array (NuSTAR) satellite to point its very sensitive X-ray telescope at the Sun. Featured here is the Sun in ultraviolet light, shown in a red hue as taken by the orbiting Solar Dynamics Observatory (SDO). Superimposed in false-colored green and blue is emission above sunspots detected by NuSTAR…

哈勃发现火焰星云中的尘埃漩涡

哈勃发现火焰星云中的尘埃漩涡

The Flame Nebula, also called NGC 2024, is a large star-forming region in the constellation Orion that lies about 1,400 light-years from Earth. It’s a portion of the Orion Molecular Cloud Complex, which includes such famous nebulae as the Horsehead Nebula and Orion Nebula. This image focuses on the dark, dusty heart of the nebula, where a star cluster resides, mostly hidden from view. Nearby (but not visible in this image) is the bright star Alnitak, the easternmost star in the Belt of Orion. Radiation from Alnitak ionizes the Flame Nebula’s hydrogen gas. As the gas begins to cool from its higher-energy state to a lower-energy state, it emits energy in the form of light, causing the visible glow behind the swirled wisps of dust….

摩天大楼上方的食月

摩天大楼上方的食月

2021年11月22日 Lunar Eclipse over a Skyscraper Image Credit & Copyright: Yuri Beletsky (Carnegie Las Campanas Observatory, TWAN) Explanation: Why is the Moon on top of this building? Planning. It took the astrophotographer careful planning — including figuring out exactly where to place the camera and exactly when to take the shot — to create this striking superposition. The single image featured was taken in the early morning hours of November 19, near the peak of the partial lunar eclipse that was occurring as the Moon passed through the Earth’s shadow. At this time, almost the entire Moon — 99.1 percent of its area — was in the darkest part of the Earth’s shadow. The building is the Gran Torre Santiago building in Chile, the tallest…

伦纳德彗星

伦纳德彗星

2021年11月21日 Introducing Comet Leonard Image Credit & Copyright: Dan Bartlett Explanation: Here comes Comet Leonard. Comet C/2021 A1 (Leonard) was discovered as a faint smudge in January 2021 when it was out past Mars — but its orbit will take the giant shedding ice-ball into the inner Solar System, passing near both Earth and Venus in December before it swoops around the Sun in early January 2022. Although comets are notoriously hard to predict, some estimations have Comet Leonard brightening to become visible to the unaided eye in December. Comet Leonard was captured just over a week ago already sporting a green-tinged coma and an extended dust tail. The featured picture was composed from 62 images taken through a moderate-sized telescope — one set of…

近乎月全食

近乎月全食

2021年11月20日 An Almost Total Lunar Eclipse Image Credit & Copyright: Robert Fedez Explanation: Predawn hours of November 19 found the Moon in partly cloudy skies over Cancun, Mexico. Captured in this telephoto snapshot, the lunar disk is not quite entirely immersed in Earth’s dark umbral shadow during a long partial lunar eclipse. The partial eclipse was deep though, deep enough to show the dimmed but reddened light in Earth’s shadow. That’s a sight often anticipated by fans of total lunar eclipses. Wandering through the constellation Taurus, the eclipsed Moon’s dimmer light also made it easier to spot the Pleiades star cluster. The stars of the Seven Sisters share this frame at the upper right, with the almost totally eclipsed Moon. Notable APOD Submissions (so far):…