TEACHER RESOURCE SCIENCE CONTENT/ CURRICULUM LINK EARTH SYSTEMS / ASTRONOMICAL SYSTEMS / STARS STARDOME OBSERVATORY & PLANETARIUM FACTS, RESOURCES AND ACTIVITIES ON... eath of our Sun The d Planetary nebula come in a huge variety of colour and symmetry. Credit: NASA (Planetary Nebula) As with all stars in the Universe, our Sun will not last forever. Most people are familiar with what happens to large stars when they die. Supernova explosions send out vast clouds of gas and dust, leaving behind neutron stars or even black holes. These violent explosions are some of the most powerful events known to us but not all stars will meet such a fiery end. Our Sun is one of them. It is not massive enough to explode in a supernova. Instead, it will slowly puff out the remaining matter back into space in what is known as a planetary nebula. These beautifully colourful, often circular, objects litter our galaxy, leaving behind white dwarf stars. When our Sun runs out of core hydrogen in about 5 billion years, nuclear fusion will stop because the temperature is insufficient to fuse helium into heavier elements. Gravity then gets the upper hand, compressing the core and raising the temperature. As the temperature rises a shell of hydrogen surrounding the core will undergo fusion Hubble snaps a beautiful show of the causing the overlying stellar envelope to expand Helix planetary nebula. outwards. As the Sun’s surface area increases, it will Credit: NASA cool to become a red giant for the next billion years. As the core continues to contract, temperatures They are also a can reach 100 million K, and the fusion of reminder of the Planetary nebulae helium into carbon and oxygen begins. amazing recycling have nothing to do with Once the core helium is consumed, process of stars. planets at all. They are the core contracts again and a shell The remaining named so because their of helium will start burning beneath heavy elements circular shape made early the hydrogen-burning shell. The that are thrown astronomers describe outer layers of our Sun will become back into space will them as ‘circular, unstable and thrown off back into eventually coalesce fading planets’ in space, becoming a planetary nebula. under gravity to form new nebulae, and eventually stars, the night sky. All that will remain in the core is a to begin the whole process again. It’s an amazing reminder white dwarf. that the heavy metals and elements that we use on Earth Planetary nebulae are the result of the deaths were forged in the cores of dying stars eons ago. of smaller stars with masses between 1-8 of our own In the famous words of astronomer Carl Sagan; Sun. Any larger and they will explode in more violent “The nitrogen in our DNA, the calcium in our teeth, events. The beautiful colours of planetary nebulae the iron in our blood, were made in the interiors of are caused by the ionization of atoms in the cloud collapsing stars. We are made of star stuff”. of elements left over. The different colours indicate different elements, like hydrogen and oxygen. Check out these other resources... Planetary nebula gallery: nasa.gov/mission_pages/chandra/multimedia/planetary_nebula.html For a more advanced resource on the topic, check out our other resource: stardome.org.nz/wp- content/uploads/2019/06/Stardome-Education-Worksheet_Stars-Part-Three.pdf What happens to the elements that are thrown into space? How long will our Sun live? Why don’t smaller stars explode in a supernovae? DISCUSSION POINTS STARDOME.ORG.NZ 09 624 1246 ACTIVITY STARDOME OBSERVATORY & PLANETARIUM WHAT'S GOING ON? Milky nebula Milk is mostly water but it also contains Make your own colourful planetary nebula! vitamins, minerals, proteins and tiny droplets of fat. Like other oils, milk fat is a non-polar molecule, meaning it doesn’t YOU 'LL NEED dissolve in water. When soap is mixed A flat tray or plate in, the non-polar (hydrophobic) portion Milk (full cream is best) of micelles (molecular soap structures Dishwashing liquid in solution) break up and collect the non-polar fat molecules. Then, the polar Cotton bud (or sponge) surface of the micelle (hydrophilic) Food colouring of your choice. connects to a polar water molecule with the fat held inside the soap micelle. WHAT TO DO Thanks to the soap connection, the 1 Take the flat dish or plate and pour in enough milk so the non-polar fat can then be carried by the bottom is covered. polar water. 2 Take your food colouring and place 1-2 drops in the centre The molecules of fat move in all of your milk dish. You can drop different colours on top of directions as the soap molecules race each other to create more colourful nebulae but be careful around to join up with the fat molecules. not to mix them with them milk too much. The added food colouring allows us to 3 Take your cotton bud (or sponge) and soak this in your watch this reaction happen that would dishwashing liquid. otherwise be invisible. This is why you 4 Take the cotton bud, and place this in the centre of your can expect milk with a higher fat content food colouring drop and hold it there. to produce larger explosions of colour! 5 You will see an explosion of colour as the food colouring We know this isn’t exactly a planetary expands out and away from the centre, creating a beautiful nebula but these chemical processes planetary nebula! nicely replicate the beautiful colour and vibrance of one! Credit: Shocking Science take a photo of your activity and send it to us. we'd love to see it! 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