「国家」这个词在英文中视语境不同。 state、nation、country 三者的含义与区别在哪里？ 卡梅伦说：「Four nations in one country」，那英国是 country，苏格兰是 nation。 那为什么联合国叫 United… 显示 …
Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names.
Stars are giant balls of hot gas – mostly hydrogen, with some helium and small amounts of other elements. Every star has its own life cycle, ranging from a few million to trillions of years, and its properties change as it ages.
This article describes the properties and evolution of individual stars. Included in the discussion are the sizes, energetics, temperatures, masses, and chemical compositions of stars.
The star originates from the Large Magellanic Cloud and probably formed directly after the first stars through dust cooling.
Stars are massive, luminous spheres of gas, mainly composed of hydrogen, with smaller amounts of helium and other elements. The lifespan of a star varies widely, generally ranging from several million to several trillion years.
How are stars named? And what happens when they die? These star facts explain the science of the night sky.
Stars are luminous spheres made of plasma – a superheated gas threaded with a magnetic field. They are made mostly of hydrogen, which stars fuse in their cores. That process releases energy, which pushes against the weight of the outer layers of the star and keeps it stable.