starlight and what it tells us l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Starlight and What it Tells Us PowerPoint Presentation
Download Presentation
Starlight and What it Tells Us

Loading in 2 Seconds...

play fullscreen
1 / 37

Starlight and What it Tells Us - PowerPoint PPT Presentation


  • 263 Views
  • Uploaded on

Starlight and What it Tells Us. The Stars in the Sky. Vary in Brightness Distance Size Vary in Color Color = Temperature. Star Names. Proper star names mostly Arabic Greek Letters, Numbers Catalog Identifiers Faint stars usually have no name. The Names of Sirius.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Starlight and What it Tells Us' - Gabriel


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
the stars in the sky
The Stars in the Sky

Vary in Brightness

  • Distance
  • Size

Vary in Color

  • Color = Temperature
star names
Star Names
  • Proper star names mostly Arabic
  • Greek Letters, Numbers
  • Catalog Identifiers
  • Faint stars usually have no name
the names of sirius
The Names of Sirius
  • Alpha Canis Majoris (Bayer, 1603)
  • 9 Canis Majoris (Flamsteed, 1725)
  • BD -16 1591 (Bonner Durchmusterung 1859-1903)
  • HR 2491 (Harvard Revised Catalog, 1908)
  • HD 48915 (Henry Draper, 1918-1924)
  • ADS 5423 (Aitken Double Star Catalog, 1932)
  • HIP 32349 (HIPPARCOS, 1997)
the heavens are not changeless
The Heavens Are Not Changeless
  • The Stars Move
    • Most of our constellations would have been unrecognizable to Neanderthal Man
  • The Solar System Moves
    • Very few of our nearby stars would have been visible to the first humans
  • Stars are Born, Live and Die
    • Many of our brightest stars did not exist in the days of the dinosaurs
brightness of stars
Brightness of Stars
  • Variations in distance and intrinsic brightness
  • Scale based on one by Hipparcos 500 B.C.
  • Magnitude: Large Numbers = Fainter
    • One magnitude = 2.5 x
    • Five magnitudes = 100 x
magnitudes
Magnitudes
  • Planet around nearby star: 30
  • Pluto: 13
  • Faintest Naked-Eye Star: 6
  • Big Dipper Stars: 2
  • Sirius (Brightest Star) -1.6
  • Venus -4
  • Full Moon -12
  • Sun -27
absolute magnitude
Absolute Magnitude
  • Altair and Deneb are about equally bright as seen from Earth
  • Altair is 16 l.y. away, Deneb 1600
  • Hence Deneb must be about 10,000 times brighter
absolute magnitude11
Absolute Magnitude
  • How bright a star would be at a distance of 32.6 l.y. (10 parsecs)
  • Sun: 4.5 (inconspicuous naked-eye star)
  • Altair: 2.2
  • Deneb: -7.1 (bright as crescent moon)
    • Note: Deneb - Altair about 10 magnitudes = 100 x 100 = 10,000 times
black body radiation
Black-Body Radiation
  • Objects Emit Radiation Because They Are Hot
  • Why “Black”? Because None of the Radiation is Reflected from Some Other Source
  • The Sun Emits Black-Body Radiation, Mars Does Not
  • Close Example of pure Black-Body radiation: Peephole in a pottery kiln
why black body radiation is so important
Why Black-Body Radiation is so Important
  • Color is directly related to temperature
  • Temperature is the only determinant of color
  • Energy per unit area is the same if temperature is the same
    • If two stars have the same color and distance, difference in brightness is due to difference in size
    • Dwarf and giant stars are literally dwarfs or giants
sirius and the pup18
Sirius and the Pup
  • Sirius M = -1.5; Pup M = 8.5
  • 10 magnitude difference
  • 100 x 100 = 10,000 times brightness distance
  • Sirius and the Pup are same color, therefore same temperature (Pup is hotter)
  • Pup must have 1/10,000 the apparent area of Sirius = 1/100 the diameter
spectroscopy
Spectroscopy
  • Different atoms absorb or emit specific wavelengths of light
  • When light spread into a spectrum, the absorbed wavelengths show up as dark (missing) bands
  • These spectral lines are indicators of:
    • Chemical composition
    • Physical conditions
spectra and spectral lines
Spectra and Spectral Lines
  • Continuous Spectrum: Incandescent solids or liquids (steel mill) and dense hot gases (Sun’s photosphere)
  • Emission Spectrum: Thin hot gases (fireworks, sodium or mercury vapor lights, Sun’s chromosphere
  • Absorption Spectrum: Light shining through thin gases (Sun and star light)
spectral lines are affected by
Spectral Lines are Affected By:
  • Electrical and Magnetic Fields
  • Number of Electrons Atoms Have Lost (Indicates Temperature and Pressure)
  • Motion (Doppler Effect)
  • Blue-shifted if Motion Toward Observer
  • Red-shifted if Motion Away From Observer
what the doppler effect tells us
What the Doppler Effect Tells Us
  • Radial Motion
  • Rotation of Stars
    • Approaching side of star blue-shifted, receding side red-shifted
  • Unseen Companions (Stars or Planets)
    • Star oscillates around center of mass
  • Surface and Interior Motions
    • Changes in Size
    • Interior Oscillations
spectral classification of stars
Spectral Classification of Stars
  • W – very hot young stars expelling their outer layers
  • Main Sequence: O, B, A, F, G, K, M (hottest to coolest)
    • “Oh be a fine girl/guy, kiss me”
  • Subdwarfs: L, T, Y (hottest to coolest)
  • Chemically Peculiar Stars: C, N, R, S
  • White Dwarfs: D
spectral signatures of stars
Spectral Signatures of Stars
  • O: Ionized Helium
  • B: Neutral Helium
  • A: Strongest Hydrogen Lines
  • F: Ionized Calcium
  • G: Strongest Calcium Lines + Neutral Metals
  • K: Neutral Metals Dominate
  • M: Titanium Oxide
the main sequence o
The Main Sequence: O
  • 30,000-60,000 K (Blue-white)
  • Absolute Magnitude -5
  • 1,000,000 times Sun’s Luminosity
  • 16 times Sun’s Diameter
  • 64 times Sun’s Mass
  • Lifetime: Less than a million years
  • Examples: Orion's Belt
the main sequence b
The Main Sequence: B
  • 10,000-30,000 K (Blue-white)
  • Absolute Magnitude -3
  • 20,000 times Sun’s Luminosity
  • 7 times Sun’s Diameter
  • 18 times Sun’s Mass
  • Lifetime: 10 million years
  • Examples: Spica
the main sequence a
The Main Sequence: A
  • Temperature: 7500-10,000 K (White)
  • Absolute Magnitude +0.5
  • 40 times Sun’s Luminosity
  • 2 times Sun’s Diameter
  • 3 times Sun’s Mass
  • Lifetime: 600 million years
  • Examples: Vega, Sirius
the main sequence f
The Main Sequence: F
  • Temperature: 6000-7500 K (Yellow-White)
  • Absolute Magnitude +2.5
  • 6 times Sun’s Luminosity
  • 1.5 times Sun’s Diameter
  • 1.7 times Sun’s Mass
  • Lifetime: 2.5 billion years
  • Examples: Procyon
the main sequence g
The Main Sequence: G
  • Temperature: 5000-6000 K (Yellow)
  • Absolute Magnitude +5
  • 1 times Sun’s Luminosity
  • 1 times Sun’s Diameter
  • 1 times Sun’s Mass
  • Lifetime: 10 billion years
  • Examples: Sun, Alpha Centauri A
the main sequence k
The Main Sequence: K
  • Temperature: 3500-5000 K (Orange)
  • Absolute Magnitude +6
  • 0.4 times Sun’s Luminosity
  • 0.9 times Sun’s Diameter
  • 0.8 times Sun’s Mass
  • Lifetime: 10 billion years
  • Examples: Alpha Centauri B
the main sequence m
The Main Sequence: M
  • Temperature: 2000-3500 K(Red)
  • Absolute Magnitude +10 to +15
  • 0.04 times Sun’s Luminosity
  • 0.5 times Sun’s Diameter
  • 0.4 times Sun’s Mass
  • Lifetime: 5 trillion years
  • 75% + of all stars
  • Examples: Barnard's Star, Proxima Centauri
sub dwarfs
Sub-Dwarfs
  • L: 1300-2000 K, Borderline stars with alkali metals and metal hydrides
  • T: 700-1300 K, Substellar, methane in spectra
  • Y <700 K, Substellar, ammonia in spectra (predicted)