Introduction to the Universe

Transcription

1 What makes up the Universe? Introduction to the Universe Book page

2 Objects in the Universe Astrophysics is the science that tries to make sense of the universe by - describing the Universe (Astronomy) - understanding its structure and origin (Cosmology) Main objects are Galaxies, Quasars and Nebulae

3 Galaxies Fast collection of stars 3 types of galaxies Quasars Extremely bright objects Very distant objects

4 Nebulae Misty pattern in night sky Stellar nurseries Others are debris of supernovas Made from gas and dust

5 Stars and Galaxies This table gives some idea of the vast distances between objects in the universe. 1 Light year is about 9 trillion kilometers (or about 6 trillion miles)

6 Our Galaxy, the Milky Way These two drawings show what our galaxy would look like from the outside; the photograph was taken in the infrared.

7 The Solar System The Sun and the 8 planets Inner Planets - solid Mercury, Venus, Earth and Mars Outer planets gas giants Jupiter, Saturn, Uranus, Neptune Pluto is not a planet. It is called dwarf planet Definition: A planet is a celestial body that a) orbits around the Sun b) has sufficient mass to reach hydrostatic (nearly round) shape c) has cleared the neighborhood around its orbit

8 New Horizons cgrahamphysics.com

9 Asteroid belt Between Mars and Jupiter

10 Asteroids Rocky bodies Large, up to 300km across Irregular shape Comets Frozen gas, ice and dust Smaller, just a few km across Follow highly elliptical path Tail points away from Sun Found in - Kuiper belt - Oort Cloud

11 Comets are found here cgrahamphysics.com

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13 Planet Facts cgrahamphysics.com

14 The Universe cgrahamphysics.com

15 Stellar cluster Stars held together by gravitational attraction All stars were created about the same time Many thousands of stars in a cluster

16 Constellation A group of stars that form a recognizable pattern as viewed from Earth Stars are not related They are very bright When moving away from Earth, the pattern is no longer recognizable Example: Big dipper, the Great Bear

17 Galaxies The next nearest galaxy, Andromeda, is some 2 million lightyears away. It is estimated that there are about as many galaxies in the universe as there are stars in our own galaxy 100 billion or so. Many galaxies occur in gravitationally bound clusters, some of which have only a few galaxies and others of which have thousands ly 10 5 ly

18 Nearest galactic object is the Magellanic Cloud

19 Local group of galaxies cgrahamphysics.com

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21 Cluster - open Cluster and Super cluster Group of stars held together by gravity All formed around same time from same nebulae Contain younger stars < 10 billion years Virgo nearest cluster to our galaxy Super cluster - globular 100s of thousands of older stars Very little gas and dust Over 11 billion years old Milky Way and Virgo are part of a super cluster

22 Stars in galaxies Stars in a galaxy are not uniformly distributed, their separation of average is m. The separation of the galaxies in clusters is of the order of m and the separation of the clusters is of the order of m.

23 Our Universe cgrahamphysics.com

24 Apparent motion of the Stars Stars rise in the East and set in the West Their position appears to be fixed to the giant celestial sphere they are referred to as fixed stars Certain celestial objects do not move in circles, but wander back and forth

25 Explanation for the observation cgrahamphysics.com

26 The nature of Stars Lighter elements such as hydrogen fuse to form helium Main source of energy for stars Very high temperatures and pressure needed in order to overcome Coulomb repulsion Stars are formed by interstellar dust coming together through gravitational attraction

27 The birth of a star cgrahamphysics.com

28 Hydrostatic EQLB The loss in PE can, if mass is high enough, produce the high temperature necessary for fusion Equilibrium between radiation pressure outward and gravitational pressure inward a stable star If initial mass is about 80% of mass of Sun, temperature reached is not high enough for fusion to take place. A hydrogen rich object called brown dwarf forms

29 Different types of stars Dwarfs White Dwarf Much smaller than the Sun Much higher surface temperature Sirius B: T = K Do not produce energy, just radiate energy Brown Dwarfs Just enough mass for fusion to produce own light, but not enough to sustain fusion Relatively cool, about Jupiter s size

30 Red Giants Considerably larger than Sun Much lower SA temperature than Sun Betelgeuse a super red giant has diameter equal to that of the distance from Jupiter to the Sun and T = 3000K

31 Neutron Stars Completely made up of neutrons Remnants of a supernova

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33 Supernovae An enormous shock wave caused by the outer layers of a star falling rapidly inwards Much of the surface of the star will be torn away in a massive explosion In 1987 the star SK69202 in the large Magellanic Cloud went supernova its brilliance was greater than that of the whole Universe by a factor of 100

34 Stephen Hawking: Supernovae cgrahamphysics.com

35 Each time a pole lines up with Earth, a pulse of radiation will be cgrahamphysics.com Rotating neutron stars They emit beams of EM radiation in range of radio frequencies from the poles of the star Pulsar

36 Black Holes After gravitational collapse stars reach a density and radius that the gravitational field at the surface of the star will be strong enough to prevent EM radiation to escape The star will not emit any light and has become a black hole The Simpsons Black Hole Sucking The singularity and spagettification Interstellar Black hole scene Interstellar - Landing in the Tesser

37 Binary Stars Many stars appear to be a single point of light to the naked eye Viewed through a telescope or by other means they are actually two stars orbiting each other Sirius, the brightest star as seen from Earth consists of Sirius A and Sirius B Sirius A is a main sequence star and Sirius B is a white dwarf