ASTR 1120 General Astronomy: Review of the Course Stars & Galaxies Four general topics: • FINAL: Saturday, Dec 12th, 7:30pm, HERE • ALTERNATE FINAL : Monday, Dec 7th, 5:30pm 1. Intro: Scales, matter, light, telescopes in Muenzinger E131 2. Stars • Last OBSERVING session, Tue, Dec.8th, 7pm 3. Galaxies • Please check your grade on clickers, midterms, 4. Cosmology/Dark Matter/Universe HWs on CU learn - e-mail Thomas if you see discrepancies/missing grade. 1. The Scale of the Universe Course Goals To develop a broad view of what we know about the Universe To understand the forces that shape the Universe and its history To help you understand how we figured all this out To learn how science works
Light: our main source of astronomical knowledge Matter: Atom electron nucleus p + e - n protons neutrons Thermal (black body) Spectra The Electromagnetic spectrum • Emitted by all solid/opaque objects, including stars, planets, humans • Smooth, broad spectrum rising to a peak at some wavelength, where most of the radiation is emitted – Wien’s Law – Stefan-Boltzmann Law
Spectral lines: By atoms emitting Telescopes or absorbing PHOTONS = light • Refracting vs Reflecting • Size matters: • The energy – Light gathering power change between – Angular resolution (diffraction limit) levels is equal to • Telescopes are built differently for different the energy of the wavelengths: ground-based, airborne and space photon. • Remember- larger energy jumps will be SHORTER wavelength photons! Stars: Starting with our Sun Stars 1. What is the Sun made of? • Shine with energy 2. How does the Sun produce its energy? released from fusion 3. Which forces keep the Sun in – hydrogen fusing into helium equilibrium? 4. What’s inside the Sun? • Overall fusion rate very stable 5. What will be the end of the Sun? – gravitational equilibrium 6. How massive is the Sun? • Violent activity on the surface
Measuring the Stars The Main Sequence • Estimating distances via parallax • Stars spend most of their lives here • Inverse square law for brightness • More massive stars are – Apparent brightness and – Rarer distance � luminosity – Hotter/Bluer – Brighter • Measuring temperatures – Shorter lived via color, spectral type – OBAFGKM • Can estimate ages of • Measuring masses via star systems from binary stars “main sequence turnoff” The Hertzsprung-Russell Diagram Stellar Evolution Stellar Evolution 1. Star Birth 1. Star Birth 2. Main Sequence 2. Main Sequence 3. Series of expansions 3. Series of expansions and deflations in and deflations in response to core response to core nuclear burning nuclear burning • Low mass stars: • Low mass stars: – Red giant – Red giant – Horizontal branch star – Horizontal branch star – Planetary nebula – Planetary nebula – White dwarf – White dwarf
Stellar High Mass Stars Graveyard • Very rapid sequence • White dwarfs fusing heavier elements up to iron – and the possibility of white dwarf supernovae – Core unsupported = collapse • Neutron stars • Supernova explosion – possible pulsars – Blasts heavy elements back into space • Black Holes • Neutron star or black – Detected only by their hole remains interactions Stellar Stellar Graveyard Graveyard • White dwarfs • White dwarfs – and the possibility of – and the possibility of white dwarf supernovae white dwarf supernovae • Neutron stars • Neutron stars – possible pulsars – possible pulsars • Black Holes • Black Holes – Detected only by their – Detected only by their interactions interactions
3. The Milky Way Galaxy 3. The Milky Way Galaxy • Our home spiral galaxy • Our home spiral galaxy – Bulge – Bulge – Halo – Halo – Disk – Disk • Star-Gas-Star Cycle • Star-Gas-Star Cycle – Gas – Gas – Dust – Dust – Stars – Stars • A supermassive black • A supermassive black hole in the Galactic hole in the Galactic Center?! Center?! – Yes – Yes 3. The Milky Way Galaxy Other Galaxies • Our home spiral galaxy – Bulge • Main Galaxy types: – Halo – Disk – Spirals – Ellipticals • Star-Gas-Star Cycle – Irregulars – Gas – Dust – Stars • Bulges/spheroids Sgr A* – Older (Population II) • A supermassive black • Disks hole in the Galactic Center?! – Forming stars today – Yes (Population I)
AGNs Central Engines “Distance Ladder” to measure universe How do AGNs emit so much light in so little space? • They are powered by accretion disks around JET supermassive black holes • In some AGNs, huge DISK jets of material are shot out at the poles. These Different standard candles are useful jets are strong radio for different distances sources. Discovery of an Galaxy Evolution Expanding Universe • Galaxy formation • Hubble’s Law – Observe galaxies at different redshifts (lookback times) • The distances – Assemble sequence between galaxies are • Galaxy interactions getting bigger! – Spirals � Ellipticals – Active and starburst • Running time galaxies backwards � age of the universe • Check via computer models of gas, gravity, and star formation
4. Cosmology/Dark Matter The Fate of the Universe • Spiral galaxy rotation curves and galaxy clusters (3 ways) suggest large amounts of DARK MATTER • Hubble constant sets – 90% of the universe is a type of matter we can’t see!! the expansion rate for • Most likely candidate: NOW – WIMPs • Probably an unidentified subatomic particle • Dark matter pulls expansion curves downwards • Upwards curve suggests DARK ENERGY pushing against gravity???! The Evidence for the Big Bang Creation • Expanding universe of the • Cosmic microwave Universe background • H/He content of the universe • Inflation
I wish you good luck with the Final Exam Carl Sagan: Author of “A Pale Blue -- please bring a #2 pencil and ID Dot” “The Demon-Haunted World”, “Contact”, “Cosmos”, … We succeeded in taking that picture [from deep space], and, if you look at it, you see a dot. That's here. That's home. That's us. On it, everyone you ever heard of, every human being who ever lived, lived out their lives. The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every … and I hope you’ve enjoyed this hopeful child, every mother and father, every inventor and explorer, course that has attempted to shed a every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, lived little light on the Universe there on a mote of dust, suspended in a sunbeam.
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