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 .
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 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 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 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 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 In about 5 billion years the Sun will become a red giant, swallowing Mercury and Venus and possibly the Earth. 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 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 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 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 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 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 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 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 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 livenext → Constellations and the night sky in winter and spring↑ back to Space This page in Markdown → https://md.mova.elamur.ai/free/en/corpora/school/space/19-how-stars-die/