秋分: 卡拉尼什巨石阵上空的日行迹

秋分: 卡拉尼什巨石阵上空的日行迹

ByNASA中文

2022年9月18日 Analemma over the Callanish Stones Image Credit & Copyright: Giuseppe Petricca Explanation: If you went outside at the same time every day and took a picture that included the Sun, how would the Sun’s position change? A more visual answer to that question is an analemma, a composite image taken from the same spot at the same time over the course of a year. The featured analemma was composed from images taken every few days at noon near the village of Callanish in the Outer Hebrides in Scotland, UK. In the foreground are the Callanish Stones, a stone circle built around 2700 BC during humanity’s Bronze Age. It is not known if the placement of the Callanish Stones has or had astronomical significance. The…

台北上空的日行迹

台北上空的日行迹

ByNASA中文

2022年6月21日 Analemma over Taipei Image Credit & Copyright: Meiying Lee Explanation: Does the Sun return to the same spot on the sky every day? No. A better and more visual answer to that question is an analemma, a composite of images taken at the same time and from the same place over the course of a year. The featured analemma was compiled at 4:30 pm many afternoons from Taiwan during 2021, with the city skyline of Taipei in the foreground, including tall Taipei 101. The Sun’s location in December — at the December solstice — is shown on the far left, while its location at the June solstice is captured on the far right. Also shown are the positions of the Sun throughout the rest…

2021年的天空

2021年的天空

ByNASA中文

2022年3月21日 The Sky in 2021 Image Credit & Copyright: Cees Bassa (Netherlands Institute for Radio Astronomy) Explanation: What if you could see the entire sky — all at once — for an entire year? That, very nearly, is what is pictured here. Every 15 minutes during 2021, an all-sky camera took an image of the sky over the Netherlands. Central columns from these images were then aligned and combined to create the featured keogram, with January at the top, December at the bottom, and the middle of the night running vertically just left of center. What do we see? Most obviously, the daytime sky is mostly blue, while the nighttime sky is mostly black. The twelve light bands crossing the night sky are caused by…

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…

巨石阵的夏至日出

巨石阵的夏至日出

ByNASA中文

2021年06月20日 Sunrise Solstice over Stonehenge Image Credit & Copyright: Max Alexander, STFC, SPL Explanation: Today the Sun reaches its northernmost point in planet Earth’s sky. Called a solstice, many cultures mark this date as a change of seasons — from spring to summer in Earth’s Northern Hemisphere and from fall to winter in Earth’s Southern Hemisphere. Precisely, the single time of solstice occurs today for some parts of the world, but tomorrow for other regions. The featured image was taken during the week of the 2008 summer solstice at Stonehenge in United Kingdom, and captures a picturesque sunrise involving fog, trees, clouds, stones placed about 4,500 years ago, and a 4.5 billion year old large glowing orb. Even given the precession of the Earth’s rotational…

北半球夏季的暮光时分

北半球夏季的暮光时分

ByNASA中文

2021年06月19日 Northern Summer Twilight Image Credit & Copyright: Justin Anderson Explanation: Nights grow shorter and days grow longer as the summer solstice approaches in the north. Usually seen at high latitudes in summer months, noctilucent or night shining clouds begin to make their appearance. Drifting near the edge of space about 80 kilometers above the Earth’s surface, these icy clouds were still reflecting the sunlight on June 14. Though the Sun was below the horizon as seen north of Forrest, Manitoba, Canada, they were caught in a single exposure of a near midnight twilight sky. Multiple exposures of the foreground track the lower altitude flash of fireflies, another fleeting apparition shining in the summer night. Tomorrow’s picture: the season’s sunrise 北半球夏季的暮光时分 影像提供与版权: Justin Anderson 说明:…

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…