冬至的太阳与银河

冬至的太阳与银河

ByNASA中文

2021年12月21日 Solstice Sun and Milky Way Composite Image Credit & Copyright: Stefan Seip (TWAN) Explanation: Welcome to December’s solstice, first day of winter in the north and summer for the southern hemisphere. Astronomical markers of the seasons, solstice and equinox dates are based on the Sun’s place in its annual journey along the ecliptic, through planet Earth’s sky. At this solstice, the Sun reaches its maximum southern declination of -23.5 degrees today at 15:59 UTC, while its right ascension coordinate on the celestial sphere is 18 hours. That puts the Sun in the constellation Sagittarius in a direction near the center of our Milky Way galaxy. In fact, if you could see today’s Solstice Sun against faint background stars and nebulae (that’s really hard to…

冬至：献上一年的日出

冬至：献上一年的日出

ByNASA中文

2020年12月21日 Solstice: Sunrises Around the Year Image Credit & Copyright: Zaid M. Al-Abbadi Explanation: Does the Sun always rise in the same direction? No. As the months change, the direction toward the rising Sun changes, too. The featured image shows the direction of sunrise every month during 2019 as seen from near the city of Amman, Jordan. The camera in the image is always facing due east, with north toward the left and south toward the right. Although the Sun always rises in the east in general, it rises furthest to the south of east on the December solstice, and furthest north of east on the June solstice. Today is the December solstice, the day of least sunlight in the Northern Hemisphere and of most…

12月的天象

12月的天象

ByNASA中文

Credit: NASA/JPL-Caltech 十二月的天空会发生什么？一场流星雨，一场木星和土星之间的罕见的近距离接触，还有冬至。 Credit: NASA/JPL-Caltech 12月带来了每年最可靠的流星雨之一，也是2020年最好的流星雨之一——双子座流星雨。这场流星雨从12月4日到17日非常活跃，因为地球在小行星法厄同3200轨道上留下的尘埃碎片的痕迹中穿行。这可能是一颗被烧毁的彗星。 双子座流星雨大多数年份都能产生大量的流星，但今年的流星雨更甚。因为流星雨的高峰期正好赶上新月的到来，因此天空变得更暗，没有月光来干扰较暗的流星，双子座流星雨在12月13日夜间至14日早晨达到高峰，前后几天都能看到一些流星活动。北半球整夜都可以观看，当地时间凌晨2点左右最活跃，而对于南半球的观众来说则是在午夜之后观看。 为了获得最佳的观赏效果，找一个远离城市灯光的安全地点，平躺在地上，双脚指向南方，双脚朝南，然后抬头往天空上看。流星可以出现在天空的任何地方，不过，它们看起来像是从双子座附近放射出来。所以，在这里愿你的天空晴朗，看到流星。 Credit: NASA/JPL-Caltech 木星和土星一整年都在一起穿越天空，但这个月，准备好让它们真正上演一出好戏吧。在12月的前三周，每天晚上观看这两颗行星在天空中的距离比它们20年来的距离都要近。在日落后的一小时内，在西南部寻找它们，而在12月21日，两颗巨大的行星将相距仅十分之一度，这大约是一枚一角硬币的厚度。这意味着这两颗行星和它们的卫星，可以通过双筒望远镜或小型望远镜在同一视野中看到。实际上，土星看起来会像木星的卫星一样靠近木星。 Credit: NASA/JPL-Caltech 这一事件被称为“伟大的合相”。这种现象在本世纪每20年发生一次，因为地球、木星和土星的轨道周期性地排成一条直线，使得这两颗外行星在我们的夜空中显得很近。即便如此，这也是木星和土星在接下来的60年里最伟大的合相，这两颗行星直到2080年才在天空中如此近距离出现。 21日也是冬至点，北半球是冬至，南半球是夏至。在冬至点这一天，无论你身在地球的哪个角落，太阳都会到达它在天空中最南端的位置。 在北半球，太阳在这一天以最低、最短的路径穿过天空。因此，在北方，冬至带来了一年中日照时间最短的一天。现在，太阳在天空中一年四季的高度变化是由地球围绕我们的恒星公转时的倾斜引起的。这种倾斜使得每个半球接收到的太阳光在每年的季节周期中上下波动。 这是十二月的月相。 Credit: NASA/JPL-Caltech 你可以在NASA.gov网站上了解所有NASA探索太阳系和太阳系以外的任务。我是来自美国宇航局喷气推进实验室的普雷斯顿·戴奇斯，这就是这个月的天象。 参考来源： https://solarsystem.nasa.gov/whats-up-skywatching-tips-from-nasa/

冬至的献礼:一年份的天空

冬至的献礼:一年份的天空

ByNASA中文

2019 December 22 Solstice Illuminated: A Year of Sky Video Credit & Copyright: Ken Murphy (MurphLab); Music: Ariel (Moby) Explanation: Can you find which day is the winter solstice? Each panel shows one day. With 360 movie panels, the sky over (almost) an entire year is shown in time lapse format as recorded by a video camera on the roof of the Exploratorium museum in San Francisco, California. The camera recorded an image every 10 seconds from before sunrise to after sunset and from mid-2009 to mid-2010. A time stamp showing the local time of day is provided on the lower right. The videos are arranged chronologically, with July 28 shown on the upper left, and January 1 located about half way down. In the…

从冬至到夏至的延时日轨图

从冬至到夏至的延时日轨图

ByNASA中文

2019 December 21 Solstice to Solstice Solargraph Timelapse Image Credit & Copyright: Sam Cornwell Explanation: The 2019 December Solstice, on the first day of winter in planet Earth’s northern hemisphere and summer in the south, is at 4:19 Universal Time December 22. That’s December 21 for North America, though. Celebrate with a timelapse animation of the Sun’s seasonal progression through the sky. It was made with solargraph images from an ingenious array of 27 pinhole cameras. The first frame from the Solarcan camera matrix was recorded near December 21, 2018. The last frame in the series finished near June 21, 2019, the northern summer solstice. All 27 camera exposures were started at the same time, with a camera covered and removed from the array once…

日行迹

日行迹

ByGotthew

2019 September 28 An Analemma of the Sun Image Credit & Copyright: Gyorgy Soponyai Explanation: This week the equinox found the Sun near the middle, but not at the crossing point, of an analemma in its annual trek through planet Earth’s skies. In this scenic view, that graceful, figure-8-shaped curve was intentionally posed above the iconic Danube River and the capital city of Hungary. Looking south from Budapest’s Margaret Bridge it combines digital frames taken at exactly the same time of day (11:44 CET) on dates between 2018 September 24 and 2019 September 15. That puts the metropolitan Pest on the left, regal Buda on the right, and the positions of the Sun on the solstice dates at the top and bottom of the analemma…

秋分：从冬至到夏至的太阳

秋分：从冬至到夏至的太阳

ByNASA中文

2019 September 23 Equinox: The Sun from Solstice to Solstice Image Credit & Copyright: Tunç Tezel (TWAN) Explanation: Today is an equinox, a date when day and night are equal. Tomorrow, and every day until the next equinox, the night will be longer than the day in Earth’s northern hemisphere, and the day will be longer than the night in Earth’s southern hemisphere. An equinox occurs midway between the two solstices, when the days and nights are the least equal. The featured picture is a composite of hourly images taken of the Sun above Bursa, Turkey on key days from solstice to equinox to solstice. The bottom Sun band was taken during the north’s winter solstice in 2007 December, when the Sun could not rise…

时长越来越长的白昼

时长越来越长的白昼

ByNASA中文

2019 June 27 时长越来越长的白昼 影像来源及版权: Gianluca Belgrado 说明：这幅持续拍摄六个月的长曝光影像将从冬至到夏至（2018年12月21日至2019年6月16日）的时间压缩成一个单一的视角。这幅不寻常的影像被称为日轨图，它是由一台高大的管状针孔相机、通过使用一张照相纸拍摄而成。这台简易的相机被固定在意大利.卡萨拉诺的一个单一地点上，并连续不断地记录太阳的日常路径，就像一道炽热的轨迹在感光纸上燃烧一样。这些轨迹上的中断和缺口是由云层造成的。在曝光结束时，我们对纸张进行扫描从而构建出这幅数字影像。当然，从12月开始，太阳轨迹会在临近北半球冬至时落在天空中的较低处。随着白昼时长的增加和6月21日夏至的来临，太阳轨迹会越升越高。 The Longer Days Image Credit & Copyright: Gianluca Belgrado Explanation: This persistent six month long exposure compresses the time from solstice to solstice (December 21, 2018 to June 16, 2019) into a single point of view. Dubbed a solargraph, the unconventional picture was recorded with a tall, tube-shaped pinhole camera using a piece of photographic paper. Fixed to a single spot at Casarano, Italy for the entire exposure, the simple camera continuously records the Sun’s daily path as a glowing trail burned into the photosensitive paper. Breaks and gaps in the trails are caused by cloud cover. At the end of the exposure, the paper was scanned to create the digital image. Of course, starting in December…