宇宙拿铁：宇宙的平均颜色

宇宙拿铁：宇宙的平均颜色

ByNASA中文

2020年12月27日 Cosmic Latte: The Average Color of the Universe Color Credit: Karl Glazebrook & Ivan Baldry (JHU) Explanation: What color is the universe? More precisely, if the entire sky were smeared out, what color would the final mix be? This whimsical question came up when trying to determine what stars are commonplace in nearby galaxies. The answer, depicted above, is a conditionally perceived shade of beige. In computer parlance: #FFF8E7. To determine this, astronomers computationally averaged the light emitted by one of the larger samples of galaxies analyzed: the 200,000 galaxies of the 2dF survey. The resulting cosmic spectrum has some emission in all parts of the electromagnetic spectrum, but a single perceived composite color. This color has become much less blue over the past…

狐皮、独角兽与圣诞树

狐皮、独角兽与圣诞树

ByNASA中文

2020年12月26日 Fox Fur, Unicorn, and Christmas Tree Image Credit & Copyright: Miguel Claro (TWAN, Dark Sky Alqueva) Explanation: Clouds of glowing hydrogen gas fill this colorful skyscape in the faint but fanciful constellation Monoceros, the Unicorn. A star forming region cataloged as NGC 2264, the complex jumble of cosmic gas and dust is about 2,700 light-years distant and mixes reddish emission nebulae excited by energetic light from newborn stars with dark interstellar dust clouds. Where the otherwise obscuring dust clouds lie close to the hot, young stars they also reflect starlight, forming blue reflection nebulae. The telescopic image spans about 1.5 degrees or 3 full moons, covering nearly 80 light-years at the distance of NGC 2264. Its cast of cosmic characters includes the the Fox…

北半球冬季的星空

北半球冬季的星空

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2020年12月25日 Northern Winter Night Image Credit & Copyright: Adam Block Explanation: Orion always seems to come up sideways on northern winter evenings. Those familiar stars of the constellation of the Hunter are caught above the trees in this colorful night skyscape. Not a star at all but still visible to eye, the Great Nebula of Orion shines below the Hunter’s belt stars. The camera’s exposure reveals the stellar nursery’s faint pinkish glow. Betelgeuse, giant star at Orion’s shoulder, has the color of warm and cozy terrestrial lighting, but so does another familiar stellar giant, Aldebaran. Alpha star of the constellation Taurus the Bull, Aldebaran anchors the recognizable V-shape traced by the Hyades Cluster toward the top of the starry frame. Tomorrow’s picture: Fox Fur, Unicorn,…

星系NGC 1055

星系NGC 1055

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2020年12月24日 Portrait of NGC 1055 Image Credit & Copyright: Martin Pugh Explanation: Big, beautiful spiral galaxy NGC 1055 is a dominant member of a small galaxy group a mere 60 million light-years away toward the aquatically intimidating constellation Cetus. Seen edge-on, the island universe spans over 100,000 light-years, a little larger than our own Milky Way galaxy. The colorful, spiky stars decorating this cosmic portrait of NGC 1055 are in the foreground, well within the Milky Way. But the telltale pinkish star forming regions are scattered through winding dust lanes along the distant galaxy’s thin disk. With a smattering of even more distant background galaxies, the deep image also reveals a boxy halo that extends far above and below the central bluge and disk of…

木星─土星大近合：有大红斑参与的盛会

木星─土星大近合：有大红斑参与的盛会

ByNASA中文

2020年12月23日 Jupiter Meets Saturn: A Red Spotted Great Conjunction Image Credit & Copyright: Damian Peach Explanation: It was time for their close-up. Two days ago Jupiter and Saturn passed a tenth of a degree from each other in what is known a Great Conjunction. Although the two planets pass each other on the sky every 20 years, this was the closest pass in nearly four centuries. Taken early in day of the Great Conjunction, the featured multiple-exposure combination captures not only both giant planets in a single frame, but also Jupiter’s four largest moons (left to right) Callisto, Ganymede, Io, and Europa — and Saturn’s largest moon Titan. If you look very closely, the clear Chilescope image even captures Jupiter’s Great Red Spot. The now-separating…

三叶星云的气柱与喷流

三叶星云的气柱与喷流

ByNASA中文

2020年12月22日 Trifid Pillars and Jets Image Credit: NASA, ESA, Hubble Space Telescope, HLA; Processing: Advait Mehla Explanation: Dust pillars are like interstellar mountains. They survive because they are more dense than their surroundings, but they are being slowly eroded away by a hostile environment. Visible in the featured picture is the end of a huge gas and dust pillar in the Trifid Nebula (M20), punctuated by a smaller pillar pointing up and an unusual jet pointing to the left. Many of the dots are newly formed low-mass stars. A star near the small pillar’s end is slowly being stripped of its accreting gas by radiation from a tremendously brighter star situated off the top of the image. The jet extends nearly a light-year and would…

冬至：献上一年的日出

冬至：献上一年的日出

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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…

火山上空的大近合

火山上空的大近合

ByNASA中文

2020年12月20日 A Volcanic Great Conjunction Image Credit & Copyright: Francisco Sojuel Explanation: Where can I see the Great Conjunction? Near where the Sun just set. Directionally, this close passing of Jupiter and Saturn will be toward the southwest. Since the planetary pair, the Sun, and the Earth are nearly in a geometric straight line, the planets will be seen to set just where the Sun had set — from every location on Earth. When can I see the Great Conjunction? Just after sunset. Since the two planets are so near the Sun directionally, they always appear in the sky near the Sun, but can best be seen when the Earth blocks the Sun but not the planets: sunset. Soon thereafter, Jupiter and Saturn will also…

日落后的近合景观

日落后的近合景观

ByNASA中文

2020年12月19日 Conjunction after Sunset Image Credit & Copyright: Alireza Vafa Explanation: How close will Jupiter and Saturn be at their Great Conjunction? Consider this beautiful triple conjunction of Moon, Jupiter and Saturn captured through clouds in the wintry twilight. The telephoto view looks toward the western horizon and the Alborz Mountains in Iran after sunset on December 17. The celestial gathering makes it easy to see Jupiter and fainter Saturn are separated on that date by roughly the diameter of the waxing crescent Moon. On the day of their Great Conjunction, solstice day December 21, Jupiter and Saturn may seem to nearly merge though. In their closest conjunction in 400 years they will be separated on the sky by only about 1/5 the apparent diameter…

天空的钻石

天空的钻石

ByNASA中文

2020年12月18日 Diamond in the Sky Image Credit & Copyright: Mariano Ribas (Planetario de la Ciudad de Buenos Aires) Explanation: When the shadow of the Moon raced across planet Earth’s southern hemisphere on December 14, sky watchers along the shadow’s dark central path were treated to the only total solar eclipse of 2020. During the New Moon’s shadow play this glistening diamond ring was seen for a moment, even in cloudy skies. Known as the diamond ring effect, the transient spectacle actually happens twice. Just before and immediately after totality, a thin sliver of solar disk visible behind the Moon’s edge creates the appearance of a shiny jewel set in a dark ring. This dramatic snapshot from the path of totality in northern Patagonia, Argentina captures…