Sirius A with his faint white dwarf companion Sirius B

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图注： This Hubble Space Telescope image highlights Sirius, the brightest star in Earth’s night sky, appearing as an intensely luminous object at the center with prominent cross-shaped diffraction spikes. These spikes, along with the saturated glow around the main star, are caused by the Sirius' light being spread out by the telescope and camera used to make this image. Slightly below and to the left of the main star, a tiny point of light marks Sirius B, a much dimmer object captured thanks to Hubble’s high sensitivity. Sirius A is an A-type star, known for its high surface temperature and strong white-blue light, while Sirius B is a compact white dwarf, the dense remnant of a star that has exhausted its nuclear fuel. Together, they form a well-known Binary star system located about 8.6 light-years from Earth. Sirius B was originally a higher mass and brighter star that burned through its hydrogen fuel more quickly than Sirius A. This led to Sirius B evolving into a red giant and eventually ending its life as a planetary nebula, leaving only the remains of its core as a white dwarf orbiting Sirius A.
来源： NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester)
来源链接

词汇表: A型星 , 双星 , 天狼星 , 白矮星
分类： 恒星

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

文件 ( 图像 1.45 MB)

The Speed of Spacecraft

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图注： This infographic is part of the "Simplifying Astronomy for Arabic Speakers" project, aiming to present scientific concepts in a simple and accessible way. The design focuses on the speed of spacecraft during the various stages of their launch, illustrating how velocity changes as the spacecraft progresses to reach the desired orbit. Details of the Stages: Stage One (Launch): The spacecraft begins its journey by launching from the launch pad with an increasing speed. The velocity in this stage is influenced by Earth's gravity and atmospheric resistance. After One Minute: The spacecraft reaches a speed of approximately 1,600 kilometers per hour (km/h), reflecting a rapid acceleration powered by its engines. After Two and a Half Minutes: The rocket boosters are jettisoned, allowing the spacecraft to reach a speed of about 4,800 km/h. At this point, the spacecraft becomes lighter, enabling it to accelerate more efficiently. Final Stage: By the end of the ascent phase, the spacecraft achieves its final speed of approximately 28,000 km/h, allowing it to enter the desired orbit around Earth. Through educational designs like this, the project provides enthusiasts with an opportunity to understand the intricate details of space missions in an engaging and simplified manner.
来源： Ali Al-Edhari ; Background image credit - NASA

词汇表: 火箭

语言： Arabic
文字系统： Arabic

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

文件 ( 图像 11.88 MB)

A binary brown dwarf system revealed

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图注： This image presents a nearby system of brown dwarfs, objects that fall between planets and stars in mass and do not sustain long-term nuclear fusion in their cores. Located about 6.5 light-years from Earth, this system (known as Luhman 16) is the third closest system to the Solar System after the Alpha Centauri system and Barnard's Star. It was initially observed as what seemed to be a single faint source of infrared light. Brown dwarfs are often difficult to study because of their low brightness, especially in visible light. However they shine brighter in infrared light due to their cooler effective temperatures. The comparison highlights the importance of observational resolution. The image at the center, taken by NASA’s Wide-field Infrared Survey Explorer (WISE), shows the system as a single blurred object due to its lower resolution (WISE has a resolution of roughly 6 arcseconds). A highlighted zoomed-in view from the Gemini South Observatory in Chile reveals that this “single” source is actually a binary system of two brown dwarfs. The improved angular resolution (roughly 0.6 arcseconds) allows astronomers to separate the two objects clearly, demonstrating how higher-resolution observations uncover hidden structures in the universe. While the Gemini telescope is situated on the Earth and thus is affected by the blurring effects of the Earth's atmosphere, it has a substantially larger mirror than the WISE telescope (8m wide vs. 40cm wide) meaning it can achieve much higher resolutions.
来源： NASA/JPL/Gemini Observatory/AURA/NSF
来源链接

词汇表: 双星 , 褐矮星 , 角分辨率 , 分辨率

授权许可： 公共领域 公共领域 图标

文件 ( 图像 1.98 MB)

Apparatus for determining the gravitional constant

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图注： Observations of the motions of the planets around the Sun, or the Moon around the Earth, could not yield the gravitational constant, as in those cases, the mass of the central body is not initially known. Measuring the gravitational constant required a situation where the masses involved had been determined independent of measuring their gravitational attraction. The device shown here was built by John Michell (1724–1793), but Michell died before he could perform the experiment. Henry Cavendish (1731–1810) inherited the device, modified it so as to suppress external disturbances, and successfully completed the experiment. Cavendish's report to the Royal Society was under the title of "Experiments to determine the density of the Earth" as, from knowledge of the gravitational constant, the gravitational acceleration at Earth's surface and the Earth's radius, one can determine the Earth's mass and its mean density. From the modern perspective, what is now known as the "Cavendish experiment" is seen as a way of determining Newton's gravitational constant G. The image shows a cross-section of the apparatus, which Cavendish had further isolated from environmental influences by putting it into a separate room and inside a wooden box. The devices allowing Cavendish to illuminate, observe and manipulate the experiment from the outside are pictured as well. The core of the experiment is a torsion balance using two small lead spheres. The restoring force of the torsion pendulum is deduced from its natural oscillation frequency in the absence of the large masses. The gravitational attraction of the small lead spheres to their larger counterparts can then be determined by measuring how far it makes the torsion pendulum masses deviate from their null position. The image is a slightly modified (cropped, contrast and brightness adjusted) version of Fig. 1 in Cavendish's article in the Philosophical Transactions of the Royal Society, Volume 88 (December 1798), pp. 469–526 [DOI: 10.1098/rstl.1798.0022]. The permission of the Royal Society to publish this image under a CC BY licenses gratefully acknowledged.
来源： Henry Cavendish in Philosophical Transactions of the Royal Society, DOI: 10.1098/rstl.1798.0022
来源链接

词汇表: 引力常数 , 万有引力
分类： 物理学

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

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A Coronal Mass Ejection

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图注： A burst of solar material can be seen erupting from the Sun in this view, illustrating a coronal mass ejection (CME)—a large eruption of plasma and magnetic field from the Sun’s outer atmosphere, or corona. These CMEs are caused by magnetic explosions in the Sun's corona. During a CME, huge amounts of electrically charged particles are launched into space at great speeds, carrying part of the Sun’s magnetic field with them. These events are driven by changes in the Sun’s magnetic structure and release vast clouds of hot gas that travel outward into the solar system. When a CME moves through space, it can interact with a planet’s magnetic field and atmosphere, sometimes creating spectacular auroras or, in strong cases, interfering with artificial satellites and power systems. CMEs are often associated with a temporary brightening of the region of the Sun where the CME originated. This is known as a solar flare. Stars other than the Sun can also have CMEs and flares. This image was taken by NASA's Solar Dynamics Observatory (SDO). This is a space mission to monitor the Sun. The image here is taken at a special wavelength which partially ionised helium emits strongly at.
来源： NASA/Goddard/SDO
来源链接

词汇表: 太阳 , 日冕物质抛射（CME）

授权许可： 公共领域 公共领域 图标

文件 ( 图像 596.22 kB)