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GALAXIAS. Optico. Infrarojo. The Galactic Disk. The disk of our Galaxy is made up of three main components:. Stars Gas Dust. The gas in between stars is the “Interstellar Medium” (or “ISM”). Like everywhere, most gas in the disk is hydrogen. Molecular (H 2 ):
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Optico Infrarojo
The Galactic Disk The disk of our Galaxy is made up of three main components: • Stars • Gas • Dust
The gas in between stars is the “Interstellar Medium” (or “ISM”) Like everywhere, most gas in the disk is hydrogen. • Molecular (H2): • Cold, dense, tightly clumped. • Stars form within molecular clouds. • “Neutral” or Atomic (HI): • Cool, less dense, less tightly clumped. • Most common phase; the reservoir for forming the next generation of stars. • “Ionized” (HII): • Hot, more diffuse. • By-product of forming young stars.
Young massive stars die out, and electrons and nuclei recombine Gas is compressed, and cools Atomic HI Molecular H2 Ionized HII Young massive O-stars form, and ionize the gas
Fountains and Blowouts SNe from newly formed massive stars can make holes in the disk, driving material out of the Galaxy or redistributing it
Blowout in M82 “starburst” galaxy… Red is “false color”, showing location of extremely hot gas detected in X-rays. Hot because the gas is mostly the “ejecta” from supernovae!
Los brazos de la galaxia son regiones de alta densidad donde ocurre la mayor parte del proceso de formación de nuevas estrellas. Por otro lado, las ondas de choque generadas por explosiones de estrellas evitan que los brazos se dispersen.
Los brazos no son rígidos; más bien son ciertas zonas que las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico. Se calcula que el Sol ya dio varias vueltas completas. En este momento, está en una zona "tranquila", al borde de un brazo secundario.
The Bulge: A Very Crowded Neighborhood The density of stars in the bulge is about 50,000 per cubic parsec By comparison, the nearest star to the Sun is 1.3 pc away!
The Galactic Halo: Ancient Stars No gas, so no star formation… …just a bunch of old stars, either by themselves or in globular clusters.
Ordered Rotation • Nearly circular orbits (like planets around the Sun) • Randomly • Highly elliptical orbits, plunging in and out of the center of the galaxy, atrandom orientations. Stuff in Galaxies moves in two basic ways…
Side View of the Milky Way The “halo” is really the “stellar halo” – turns out there’s actually a larger halo we can’t even see! Globular clusters live in the halo
Observational tracers of magnetic fields Polarization of starlight:perpendicular field in 2 or 3 kpc orientation // B⊥ ------------- 9000 stars Zeeman splitting: parallel field, in situ (masers, clouds) △ ∝ B// ------ 30 masers Polarization at infrared, mm:perpendicular field orientation // B⊥------ clouds & star formation regions Synchrotron radiation:vertical field structures (added) total intensity S ∝ B⊥2/7, p%∝ B⊥u2 / B⊥t2 Faraday rotation:parallel field, integrated (the halo & disk) RM∝∫ne B//ds ------ 500 pulsars + >1000 EGSes
Large-scale magnetic field in the Galactic disk The largest coherent field structrue detected in the Universe!
The Milky Way: A Barred Spiral Galaxy The Milky Way is a “spiral” galaxy, sometimes also called a “late type” galaxy.
Side View “edge-on” Top View “face-on”
Elliptical Galaxies (or just “ellipticals”) • No disk! old! “spheroidals”
Early Types Late Types Unbarred and Barred Spirals Ellipticals Lenticulars
Varying amounts of bulge & disk components suggests different formation & evolution history On average… • Older Stars • Gas Poor • More Massive • On-going Star Formation • Gas Rich • Less Massive
Early-Type Galaxies from the Sloan Digital Sky Survey (SDSS)
Late-TypeGalaxies From SDSS (red because of dust)
There are galaxies beyond the Hubble Sequence that continue this trend. ??? “Dwarf” or “Irregular” Galaxies
“Dwarf” or “Irregular” galaxies tend to have more chaotic appearances… • Low mass (107-109 stars, vs 1010 for spirals) • High star formation rates (usually) • No obvious bulge or spiral patterns. • Most numerous type of galaxy in the Universe!
“Gas Infall” • Galaxies continue to form stars. • Just enough gas in galaxy disks today to form stars for <109 years. • Fresh gas must keep it going. • Fraction of metals (non-H, He) in stars is lower than expected. • Fresh Hydrogen must be flowing in.
“Merging” or “Galaxy Interactions” • Gravity pulls galaxies together! • They can orbit each other & eventually merge!
“Minor Mergers” We know this is currently happening…
Neptuno Urano Saturno Júpiter Marte Tierra Venus Mercurio
Start +4 /10 Reality: Mercure 0 4 0.4 0.39 Venus 3 7 0.7 0.72 Earth 6 10 1.0 1.00 Mars 12 16 1.6 1.5 Asteriod b 24 30 3.0 2.8 Jupiter 48 52 5.2 5.2 Saturn 96 100 10.0 9.5 Uranus 192 196 19.6 19.2 Neptune 384 388 38.8 30.0
The Kuiper Belt – home for short-period comets and dwarf planets Starting in 1992, astronomers have become aware of a vast population of small bodies orbiting the sun beyond Neptune. There are at least 70,000 "trans-Neptunians" with diameters larger than 100 km in the radial zone extending outwards from the orbit of Neptune (at 30 AU) to 50 AU.
En los últimos quince años hemos descubierto una gran cantidad de sistemas planetarios en distintos niveles de evolución.
