--- title: How stars die — a lesson of Mova's school · trees and pragmatics description: «How stars die», a lesson of the space course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: When a star like the Sun runs short of hydrogen in its core, it swells into a red giant hundreds of times wider; in about 5 billion years the Sun will do this --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/) [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/) / How stars die # How stars die Lesson 19 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/19-how-stars-die/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/0/) — When a star like the Sun runs short of hydrogen in its core, it swells into a red giant hundreds of times wider; in about 5 billion years the Sun will do this, swallowing Mercury and Venus and possibly the Earth. - [1](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/1/) — Then it gently puffs off its outer layers as a glowing shell, a planetary nebula, and what is left is a white dwarf: about the size of the Earth but so packed that a teaspoon of it would weigh more than a car. - [2](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/2/) — Stars more than about 8 times as heavy as the Sun die violently in a supernova, an explosion that for weeks can outshine a whole galaxy, like a firework that briefly lights up a whole city. - [3](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/3/) — The collapsed core can become a neutron star, only about 20 km across, as wide as a city, yet heavier than the Sun; spinning ones sweep radio beams past the Earth like a lighthouse, and we call them pulsars. - [5](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/5/) — When a star like the Sun runs short of hydrogen in its core, it swells into a red giant hundreds of times wider than before. - [6](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/6/) — In about 5 billion years the Sun will become a red giant, swallowing Mercury and Venus and possibly the Earth. - [7](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/7/) — At the end of its giant stage, a Sun-like star gently puffs off its outer layers as a glowing shell called a planetary nebula. - [8](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/8/) — What remains of a Sun-like star is a white dwarf, about the size of the Earth but with roughly half the Sun's mass, so a teaspoon of it would weigh several tonnes, more than a car. - [9](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/9/) — Stars more than about 8 times as heavy as the Sun end in a supernova, an explosion that for weeks can outshine a whole galaxy. - [10](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/10/) — In 1054 Chinese astronomers recorded a "guest star" bright enough to see by day for weeks, and its remains are the Crab Nebula in Taurus. - [11](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/11/) — In February 1987 a supernova in the Large Magellanic Cloud, a small galaxy next to ours, became visible to the naked eye from the southern hemisphere, though not from northern lands like Britain; it was the closest seen since 1604. - [12](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/12/) — A collapsing core can become a neutron star, only about 20 km across but heavier than the Sun, so a teaspoon of it would weigh billions of tonnes. - [13](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/13/) — In 1967 Jocelyn Bell Burnell, a student from Northern Ireland, discovered pulsars, spinning neutron stars that sweep beams of radio waves past the Earth like a lighthouse. - [15](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/15/) — Betelgeuse, Orion's red shoulder, is a dying red supergiant that will explode as a supernova sometime within about the next 100,000 years; nobody can say exactly when. - [16](https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/16/) — A planetary nebula has nothing to do with planets; it got the name because it looked like a round planet in old telescopes. - ← previous: [How stars live](https://md.mova.elamur.ai/free/en/corpora/school/space/18-how-stars-live/) - next →: [Constellations and the night sky in winter and spring](https://md.mova.elamur.ai/free/en/corpora/school/space/20-constellations-and-the-night-sky-in-winter-and-spring/) - ↑ back to [Space](https://md.mova.elamur.ai/free/en/corpora/school/space/)