presentsa production INTRODUCTION TO THE UNIVERSE based on the IB Astrophysics option 1
INTRODUCTION TO THE UNIVERSE What is there in the Universe? Asteroids and comets Moons Planets Stars Nebulae Stellar clusters Galaxies Galactic clusters
The Solar SystemRELATIVE SIZES: if Sun = 100, Earth =1 ...... and the distance between them is 10 000 They all orbit the Sun on elliptical paths
The SunMass: 1.99 x 1030 kgRadius:6.96 x 108 mSurface temperature: 5800 K
Planets Data (and Pluto)Planet Picture Distance to the Radius (km) Orbital Orbital Surface Density/ Satellite Sun (km) period period day temp g/cm3 s around its (ºC) water=1Mercury 58 million 4 878 km axis 59 days 88 days 167 5,43 0Venus 108 million 12 104 km -243 days 225 days 464 5,24 0 Earth 149,6 million 12 756 km 23, 93 h 365,2 15 5,52 1 days Mars 228 million 6 794 km 24h 37min 687 days -65 3,04 2Jupiter 778 million 142 800 km 9h 50min 12 years -110 1,32 +63 30sSaturn 1 427 million 120 000 km 10h 14min 29,5 years -140 0,69 +56Uranus 2 870 million 51 800 km 16h 18min 84 years -195 1,27 27Neptune 4 497 million 49 500 km 15h 48min 164 years -200 1,77 13 Pluto 5 900 million 2 400 km 6 days 248 years -225 2 1
Mercury and VenusThe rocky planets closest to the Sun
Earth and Moon Mariner 10Many planets have moons which orbitthe planet (which orbits the Sun)
MarsThe fourth of the inner planetsSpirit Rover: Mars’ West Valley
Asteroid Belt Ceres (480km): it was the first asteroid to be seen. Now it’s a dwarf planet. Mathilde (52km) Eros (13x13x33km)
Jupiter The largest gas giant, 5 times more distant from the Sun than the EarthJupiter and its moons: Io, Approximate size comparisonEuropa, Ganymede and Callisto of Earth and Jupiter
Saturn Nearly twice as far from the Sun as JupiterA rough comparison of the sizesof Saturn and Earth
UranusTwice as far from the Sun as Saturn Size comparison of Earth and Uranus
Neptune Nearly twice as far from the Sun as Uranus (30 times further than Earth)Size comparison of Neptune andEarth.
Astronomical units of distanceThe Astronomical Unit (AU) – this is the averagedistance between the Earth and the Sun. 1 AU = 150 000 000 km = 1.5x1011m
Astronomical distancesThe light year (ly) – this is the distance travelled by light inone year. c = 3x108 m/s t = 1 year = 365.25 x 24 x 60 x 60= 3.16 x 107 s Speed =Distance / Time Distance = Speed x Time = 3x108 x 3.16 x 107 = 9.46 x 1015 m 1 ly = 9.46x1015 m
Relative distances The Moon is 1.3 light seconds from the Earth The Earth is 500 light seconds from the Sun The nearest star to the Sun is about 4 light years away The diameter of a galaxy is about 100 000 light yearsThe distance between galaxies is about 1 000 000 light years
Galaxies A galaxy is a collection of a very large number of stars(around 100 thousand million) mutually attracting each otherthrough the gravitational force and staying together. Thenumber of stars varies between a few million and hundredsof billions. There are approximately 100 thousand milliongalaxies in the observable universe. There are three types of galaxies: - Spiral (Milky Way) - Elliptical (M49) - Irregular (Magellanic Clouds)
Spiral Galaxies Spiral galaxies consist of a rotating disk of starsalong with a central bulge of generally older stars.Extending outward from the bulge are relatively brightarms. There is a supermassive black hole at thecentre. The dark patches in the picture is interstellardust. Milky Way
Spiral GalaxiesAndromeda galaxy is the closest large galaxy to Earth. It coversabout the same area of the night sky as the Moon but is muchdimmer.
Elliptical Galaxies M49 ESO 325-G004Elliptical cross-section and no spiral arms.They range in shape from nearly spherical to highly flattenedellipsoids and in size from hundreds of millions to over onetrillion stars.In the outer regions, many stars are grouped into globularclusters.
Irregular Galaxies Irregular galaxies have no specific structure. TheLarge and Small Magellanic Clouds, the nearestgalaxies, are an example of irregular galaxies. Small Magellanic Cloud Hoags Object, a ring galaxy.
Stellar cluster A group of stars withina galaxy which are closeto each other, probablyheld together bygravitational attraction.They are all in the samedirection from Earth andthe same distance away.A stellar cluster cancontain from hundredsto millions of stars. Messier 69 a globular cluster, part of the Milky Way is 30 000 ly distant and 42 ly across.
Constellations A group of stars in arecognizable pattern thatappear to be near eachother in space. They are inthe same direction fromEarth but are notnecessarily the samedistance away. Orion includes Bellatrix (250 ly); Betelgeuse (640 ly); Rigel (860 ly)
How the stars seem to move The night sky seems to rotate around a point above the Earth’s axis of rotation. In 24 hours, it completes a full circle.Over the course of a year, the stars are in a slightly differentposition each night due to the Earth’s tilt.Stars which are closer to the Earth also move relative to thebackground of more distant stars due to the Earth’s orbitaround the Sun.
Nebulae Nebulous means ‘cloud-like’Originally, ‘nebula’ was a general name for any extendedastronomical object (the Andromeda Galaxy was referred to asthe Andromeda Nebula before galaxies were discovered byEdwin Hubble). Nowadays, several different astronomicalobjects are known as ‘nebulae’.A nebula can be an interstellar cloud of dust, hydrogen gas andplasma. These nebulae are often star-forming regions, such asthe Eagle nebula.A nebula can also refer to the remains of a dying star, aplanetary nebula (eg Cat’s Eye nebula).Or it can be a supernova remnant (eg Crab nebula).
NebulaeEagle Nebula and the Cone nebula: star-forming regions