--- title: Stars: what they are — a lesson of Mova's school · trees and pragmatics description: «Stars: what they are», a lesson of the space course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: The Sun is a star, quite an ordinary one: it looks so huge and bright only because it is about 270,000 times closer to us than the next nearest star. --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [Space](https://md.mova.elamur.ai/free/en/corpora/school/space/) / Stars: what they are # Stars: what they are Lesson 17 of the space course of Mova's primary school: 15 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: [the lesson at school](https://md.mova.elamur.ai/free/en/school-run/space/17-stars-what-they-are/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/0/) — The Sun is a star, quite an ordinary one: it looks so huge and bright only because it is about 270,000 times closer to us than the next nearest star. - [1](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/1/) — A star is a giant ball of hot gas, mostly hydrogen and helium, that makes its own light: deep in the Sun's core, at about 15 million °C, hydrogen is squeezed into helium and gives out enormous energy. - [2](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/2/) — A star's colour tells its temperature, just like a piece of metal in a fire that glows dull red, then yellow, then white as it gets hotter: red stars are coolest and blue-white stars hottest. - [3](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/3/) — Stars twinkle because their light passes through moving layers of warm and cool air that bend it this way and that, like a coin at the bottom of a wobbling pool. - [4](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/4/) — Most stars in our galaxy are dim red dwarfs, too faint to see with the naked eye, and many stars come in pairs or groups, like Sirius, the brightest star of the night, and its tiny white dwarf partner. - [5](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/5/) — The Sun is a star, an ordinary one, and it looks so different from the others only because it is about 270,000 times closer than the next nearest star. - [6](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/6/) — A star is a huge ball of hot gas, mostly hydrogen and helium, that makes its own light. - [7](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/7/) — Deep in the Sun's core, at about 15 million °C, hydrogen nuclei are squeezed together to make helium, releasing enormous energy. - [8](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/8/) — The Sun is about 109 times wider than the Earth, and about 1.3 million Earths could fit inside it. - [9](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/9/) — Star colours show their temperature: red stars are coolest at about 3,000 °C, the Sun is yellow-white at about 5,500 °C, and blue-white stars can be over 20,000 °C. - [10](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/10/) — Stars twinkle because their light passes through moving layers of air of different temperatures that bend it this way and that. - [11](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/11/) — Most stars in our galaxy are red dwarfs, smaller, cooler and dimmer than the Sun, and not one of them is bright enough to see with the naked eye. - [12](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/12/) — Sirius in Canis Major is the brightest star in the night sky, about 25 times brighter than the Sun in real power and about 8.6 light years away (a light year is the distance light travels in a year), which is near for a star. - [13](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/13/) — Many stars are not alone but come in pairs or groups orbiting each other, and Sirius has a tiny white dwarf partner. - [15](https://md.mova.elamur.ai/free/en/corpora/school/space/17-stars-what-they-are/15/) — Many bright stars have Arabic names, such as Aldebaran, Betelgeuse and Altair, because medieval astronomers in the Islamic world kept and improved Greek star catalogues. - ← previous: [Meteors, meteorites and shooting stars](https://md.mova.elamur.ai/free/en/corpora/school/space/16-meteors-meteorites-and-shooting-stars/) - next →: [How stars live](https://md.mova.elamur.ai/free/en/corpora/school/space/18-how-stars-live/) - ↑ back to [Space](https://md.mova.elamur.ai/free/en/corpora/school/space/)