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Galaxies. Spring 2009. Announcements. Current moon phase: waxing crescent. Planetarium trip Monday , May 4th. Show starts at 7:30 sharp. Location: http://www.astro.umass.edu/~salberts/astro103/tuesday/ Any transportation issues? No class on Tuesday, May 5th.

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galaxies

Galaxies

Spring 2009

announcements
Announcements
  • Current moon phase: waxing crescent.
  • Planetarium trip Monday, May 4th.
    • Show starts at 7:30 sharp.
    • Location: http://www.astro.umass.edu/~salberts/astro103/tuesday/
    • Any transportation issues?
  • No class on Tuesday, May 5th.
  • Last class is Tuesday, May 12th:
    • Moon Projects due
    • candy + snacks
slide3
Quiz!

Format: 20 questions; identify const.,

short answer, and multiple choice

  • Topics
    • Constellations (no mythology) & Objects We’ve Seen
    • The Moon
    • Planets (Venus and Saturn)
    • Angles & Coordinates
    • Seasons & the Sun
    • HR Diagrams
  • Things We’ve Seen
    • Ursa Major
    • Ursa Minor
    • Cassiopeia
    • Cepheus
    • Taurus
      • Pleiades
    • Gemini
    • Orion
      • Orion’s Belt
      • Betelgeuse
      • Rigel
    • Leo
    • Canis Major
      • Sirius
    • Bootes
types of galaxies spiral
Types of Galaxies - Spiral

NGC 4594: “Sombrero Galaxy”

M51:

“Whirlpool Galaxy”

NGC 1300

NGC 4414

spiral galaxies
Spiral Galaxies
  • M81: Different features stand out at different wavelengths.
    • Blue: UV light - tracing high energies, star formation, and young stars
    • Red: red visible light - lower energy, and older star populations
types of galaxies irregulars
Types of Galaxies - Irregulars

NGC 1569

Large Magellanic Cloud

M82

our galaxy the milky way
Our Galaxy: The Milky Way
  • Barred spiral
  • Over 100 billion stars
  • The sun is about 25,000 light years from the center (near Orion Spiral Arm)
  • Something menacing lurking in the center…
black hole
Black Hole!
  • Object with such a strong gravitational pull that even light can’t escape
  • All large galaxies feature a super-massive black hole in the center
  • Singularity – place of infinite density (say what?!) in the middle
  • Event Horizon – point of no return. If you cross this boundary, you can never escape.
black hole12
Black Hole!
  • Black holes can have any mass
  • Schwarzschild radius:
    • Size to which an object must be squeezed down to make it into a black hole.

G = Grav. Constant

= 6.67 x 10-11 m3 kg-1 s-2

m = mass (kg)

c = speed of light

= 3.0 x 108 m s-1

The Sun:

3 km (1.8 miles)

Earth:

0.4 inches

You:

1 x 10-25 meters

(10 billion times smaller than an electron)

will the lhc destroy the planet
Will the LHC Destroy the Planet???
  • Large Hadron Collider:
    • smash iron nuclei together at nearly the speed of light (why???)
  • Nothing to worry about because:
    • Odds of making black hole: 1 in 50 million
    • Microscopic black hole would be harmless (Hawking Radiation)

Collision Energy:

1148 TeV = 1.84 x 10-4 Joules

mBH = E/c^2 = 2.04 x 10-21 kg

Black Hole Evaporation Timescale:

tev = 8.41 x 10-17 [mBH (kg)]3 sec

Black hole would evaporate in 1 x 10-78 sec!

more surprises with galaxies
More Surprises with Galaxies
  • Fritz Zwicky
    • Estimated masses of galaxies to calculate total cluster mass
    • Measured velocities of galaxies in Coma Supercluster (how?)
  • Result:
    • Galaxies are moving way too fast!
    • Cluster should be flying apart, but it’s not.
  • What does this mean? Either:
    • Physics is wrong.
    • There’s “missing mass” in this cluster.

DARK MATTER

more evidence for dark matter
More Evidence for Dark Matter
  • Rotation Curve: how fast things are orbiting in a galaxy compared to their distance from the center
  • Stars are orbiting way too fast in our galaxy.
    • Galaxies should also be flying apart!
    • … unless there’s hidden mass.
what is dark matter
What is Dark Matter?
  • MAssive Compact Halo Objects (MACHOs)
    • black holes
    • white dwarfs
    • neutron stars
    • brown dwarfs
  • Weakly Interacting Massive Particles (WIMPs)
    • neutrinos
    • some exotic particles we have yet to prove the existence of (LHC!)

Not enough to account for most of the dark matter.

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