Space Review.pptx

Space Review Space Topics Light year distances Star brightness HR Diagrams Stellar lifecycles The big bang Evidence for the big bang CMBR Red shift Light speed Things are so far that we measure a distance in the time it takes light to travel that distance in 1 Earth year....

Space Review Space Topics Light year distances Star brightness HR Diagrams Stellar lifecycles The big bang Evidence for the big bang CMBR Red shift Light speed Things are so far that we measure a distance in the time it takes light to travel that distance in 1 Earth year. This is where the measurement ‘light year’ comes from. Light is the fastest thing in the universe, it is the speed limit. Light travels at around 300,000 km/s It can travel around the earth 7.5 times in 1 second How to calculate a light year How far does light travel in 1 year? 365 days x 24 hours x 60 minutes x 60 seconds = 31,536,000 seconds in a year km Questions Jupiter is 742,560,000 km from Earth, calculate how long it takes light to travel from Jupiter to Earth? The andromeda galaxy is 2.34x1019 km from Earth, how many light years away is this? Light takes 2.5 years to reach an object in space, how many kilometres away is the object? Stellar lifecycle – Birth of a star All stars are born in a Nebula. Large masses of gas and dust ‘clump’ together and under pressure and density. Eventually the pressure is high enough and hot enough for HYDROGEN FUSION to begin. Once the star stabilises, it becomes classified as a main sequence star. Stellar lifecycle – Main Sequence All stars start as main sequence stars and fuse Hydrogen to Helium A stars mass determines how hot and bright it will be. The more mass, the hotter the star, the brighter it will burn! The mass also determines how long a star will live and what will happen to it in the end of its life. The end of a stars life can go two different ways depending on how massive it is (how much mass it has)  Death of a Star – Average Star An average size star will not fuse helium in its core. The hydrogen fusion will continue, but not in the core, in the atmosphere of the star. This causes the star to expand and become a ‘Red Giant’ Eventually the atmosphere will ‘float away’ and become a ‘Planetary Nebula’, leaving the Helium core. This core is classified as a ‘White Dwarf’ The helium core will cool down and become a brown dwarf!  Death of a Star – Massive Star A massive size star WILL fuse past helium in its core, all the way to Iron. The hydrogen fusion will continue, but not in the core, in the atmosphere of the star. This causes the star to expand and become a ‘Red Super Giant’ There is not enough energy to push against gravity and the core collapses in seconds. This implosion causes an explosion and a SUPERNOVA The core will either start fusing protons and neutrons to become a Neutron star OR the core collapses and forms a black hole Questions How do stars begin? What causes an average star to become a red giant? How is this different to Supergiants? What determines if a star will become a red giant or a supergiant? What is the core of a white dwarf? What happens to a white dwarf? HR Diagram Plots Brightness against temperature of a star The temperature INCREASES as you move toward the centre of the graph Every star starts in the main sequence and later in its life moves off the main sequence Magnitude Apparent Magnitude – how bright it appears to be from earth. Absolute Magnitude – how bright the star would appear from 32.6 light years away from it. (10 Parsecs) The brighter the object the lower value of its Magnitude. Sun is -26.74 apparent, 4.83 absolute. Betelgeuse is 0.42 apparent, -6.02 absolute. Questions A Star A has -6 Absolute magnitude and 0.5 Apparent magnitude. Star B has -0.2 Absolute magnitude and -1 Apparent Magnitude. Explain why Star B is closer to Earth.classification would What Aldebaran be? What can you determine about its life cycle from this? What is the difference between Blue and Red super giants? What is the absolute magnitude and temperature of the Sun?