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Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine tomburbine@astro.umass.edu. Course. Course Website: http://blogs.umass.edu/astron101-tburbine/ Textbook: Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny .

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slide1
Astronomy 101The Solar SystemTuesday, Thursday2:30-3:45 pmHasbrouck 20Tom Burbinetomburbine@astro.umass.edu
course
Course
  • Course Website:
    • http://blogs.umass.edu/astron101-tburbine/
  • Textbook:
    • Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny.
    • You also will need a calculator.
office hours
Office Hours
  • Mine
  • Tuesday, Thursday - 1:15-2:15pm
  • Lederle Graduate Research Tower C 632
  • Neil
  • Tuesday, Thursday - 11 am-noon
  • Lederle Graduate Research Tower B 619-O
homework
Homework
  • We will use Spark
  • https://spark.oit.umass.edu/webct/logonDisplay.dowebct
  • Homework will be due approximately twice a week
astronomy information
Astronomy Information
  • Astronomy Help Desk
  • Mon-Thurs 7-9pm
  • Hasbrouck 205
  • The Observatory should be open on clear Thursdays
  • Students should check the observatory website at: http://www.astro.umass.edu/~orchardhill for updated information
  • There's a map to the observatory on the website.
final
Final
  • Monday - 12/14
  • 4:00 pm
  • Hasbrouck 20
no class this tuesday
No class this Tuesday
  • Space Station Bound: A Day in the Life of a Scientist Astronaut with Cady Coleman '91PhD
  • Tuesday, October 13, 2009 • 4:00 pm
  • Engineering Lab II • Room 119
  • Free Admission
slide9
HW #7
  • Due next Thursday
slide10
HW #8
  • Due next Thursday
october 9 tomorrow 7 30 am
October 9 (Tomorrow): 7:30 AM
  • LCROSS (Lunar Crater Observation and Sensing Satellite)
  • LCROSS’ spent Upper-Stage Centaur Rocket will crash into the Moon;s South Pole
  • LCROSS will then follow into the Moon
  • Looking for water
  • http://www.youtube.com/watch?v=NQ8d2Oacv2M
new rings around saturn
New Rings around Saturn
  • Seen in the infrared by the Spitzer Telescope
  • Made of dust and ice; Dust is 80 Kelvin
  • Lies some 13 million km from the planet
  • Tilted 27 degrees from main ring plane
  • 50 times more distant than the other rings and in a different plane.
  • Probably made up of debris kicked off Saturn's moon Phoebe by small impacts.
why infrared for dust
Why infrared for dust?
  • Cold things give off more light in infrared than visible
blackbody
Blackbody
  • A black body is an object that absorbs all electromagnetic radiation that falls onto it.
  • Perfect emitter of radiation
  • Radiates energy at every wavelength

http://www.daviddarling.info/images/blackbody.jpg

slide15

Stefan-Boltzman Law - energy radiated per unit surface area of a black body in unit time is directly proportional to the fourth power of the black body’s temperature

  • Wien’s Law - blackbody curve at any temperature has essentially the same shape as the curve at any other temperature, except that each wavelength is displaced, or moved over, on the graph
slide16
Stars and planets act can be modeled as blackbodies

http://www.astro.ncu.edu.tw/contents/faculty/wp_chen/Ast101/blackbody_curves.jpg

blackbody curves
Blackbody curves
  • http://www.mhhe.com/physsci/astronomy/applets/Blackbody/frame.html
slide18

http://www.rap.ucar.edu/general/asap-2005/Thur-AM2/Williams_DoD_Satellites_files/slide0005_image020.gifhttp://www.rap.ucar.edu/general/asap-2005/Thur-AM2/Williams_DoD_Satellites_files/slide0005_image020.gif

power
Power
  • Power is in Joules/second = Watts
stefan boltzman law
Stefan-Boltzman Law
  • Emitted power per square meter of surface = σT4
  • Temperature in Kelvin
  • σ = 5.7 x 10-8 Watt/(m2*K4)
  • For example, if the temperature of an object is 10,000 K
  • Emitted power per square meter = 5.7 x 10-8 x (10,000)4
  • Emitted power per square meter = 5.7 x 10-8 x (1 x 1016)
  • Emitted power per square meter = 5.7 x 108 W/m2
wien s law
Wien’s Law
  • Wavelength of Maximum intensity of the blackbody curve peak = 2,900,000 nm

T (Kelvin)

  • λmax = 2,900,000/10,000 nm
  • λmax = 290 nm
  • 1 nanometer = 1 x 10-9 meters
  • λmax = 290 nm = 2.0 x 10-7 meters
when you observe an astronomical body
When you observe an astronomical body
  • You measure intensity
  • Intensity – amount of radiation
when you see an object in the sky
When you see an object in the sky
  • You measure its brightness
  • Its brightness is a function of its
    • Distance from Earth (can be calculated from orbit)

If star:

-Luminosity - is the amount of energy a body radiates per unit time

If planet

    • Albedo
    • Size
inverse square law
Inverse Square Law
  • The apparent brightness varies inversely by the square of the distance (1/d2)
  • If the Earth was moved to 10 Astronomical Units away, the Sun would be 1/100 times dimmer
  • If the Earth was moved to 100 Astronomical Units away, the Sun would be 1/10000 times dimmer
slide27
If the Earth was moved to 1 x 108 Astronomical Units away, the Sun would be …

A) 1 x 10-12 times dimmer

B) 1 x 10-14 times dimmer

C) 1 x 10-16 times dimmer

D) 1 x 10-18 times dimmer

E) 1 x 10-20 times dimmer

slide28
If the Earth was moved to 1 x 108 Astronomical Units away, the Sun would be …

A) 1 x 10-12 times dimmer

B) 1 x 10-14 times dimmer

C) 1 x 10-16 times dimmer

D) 1 x 10-18 times dimmer

E) 1 x 10-20 times dimmer

luminosity distance formula
Luminosity-Distance Formula
  • Apparent brightness = Luminosity

4 x (distance)2

Usually use units of Solar Luminosity

LSun = 3.8 x 1026 Watts

magnitude system
Magnitude System

brightest asteroid

4 Vesta

  • Brighter –lower number

http://www.astronomynotes.com/starprop/appmag.gif

initially
Initially
  • Everybody observed with their eyes
slide37

Parallel light

Lens

Figure 7.2a

why are telescopes better than your eyes
Why are Telescopes better than your eyes?
  • They can observe light in different wavelength regions (eyes can only see visible light)
  • They can collect more light than eyes
  • They can be built to compensate for the distorting effects of the atmosphere
all large modern telescopes are reflectors
All large modern telescopes are reflectors
  • Since light passes through the lens of a refracting telescope,
  • You need to make the lens from clear, high-quality glass with precisely shaped surfaces
it is
It is
  • Its easier to make a high-quality mirror than a lens
slide46
Also,
  • Large lenses are extremely heavy
slide47
Also
  • Lens focuses red and blue light slightly differently
  • Called chromatic aberration

http://en.wikipedia.org/wiki/File:Lens6a.svg

slide48
Also
  • Light can be absorbed by the glass as it passes through the glass
  • Minor problem for visible, but severe for ultraviolet and infrared light
size of a telescope
Size of a telescope
  • Diameter of its primary mirror or lens
  • Light collecting area is proportional to the diameter squared since
  • Collecting area =  r2
  • E.g., 8-meter telescope
slide50

a

b

  • Telescope that took image b is twice as big as telescope that took image a
  • Larger the telescope, more detail can be seen
slide51
Telescope on Mauna Kea (14,000 feet high)
  • Telescope is Japanese Subaru 8-m telescope
atmosphere
Atmosphere
  • Atmosphere can absorb light
  • Atmosphere can scatter light
  • Atmosphere can distort light (twinkling)
twinkling
Twinkling
  • Twinkling of stars is caused by moving air currents in the atmosphere.
  • The beam of light from a star passes through many regions of moving air while on its way to an observer’s eye or telescope.
  • Each atmospheric region distorts the light slightly for a fraction of a second.
advantages of space based telescopes
Advantages of space-based telescopes
  • It can be open 24 hours, 7 days of week
  • Do not have to worry about distorting effects of atmosphere
  • There is no extra background of light due to scattering of light in the Earth’s atmosphere
  • Observe in more wavelength regions
slide57

http://www.scienzagiovane.unibo.it/English/radio-window/images/radiazioni-em.jpghttp://www.scienzagiovane.unibo.it/English/radio-window/images/radiazioni-em.jpg

slide58
Infrared light absorbed by molecules

http://www.ucar.edu/learn/1_3_1.htm

light in space can be affected by dust
Light in space can be affected by dust

http://www.ipac.caltech.edu/2mass/outreach/survey.html

http://en.wikipedia.org/wiki/File:Rayleigh_sunlight_scattering.png

it does not help
It does not help
  • That you are closer to the stars
to measure light
To measure light
  • In the past, they used photographic plates
  • Now they use CCDs (charge-coupled devices)
  • CCD are electronic detectors
  • CCDs are chips of silicons
slide65
CCDs
  • CCDs convert light into electrons

Shared the 2009

Physics Nobel Prize

for their discovery

William Boyle George Smith

how do they work
How do they work?
  • The CCD is made up of pixels.
  • As the light falls on each pixel, the photons become electrons due to the photoelectric effect. The photoelectric effect happens when photons of light hit the silicon of the pixel and knock electrons out of place.
  • These electrons are then stored.
  • Essentially, the charge in each row is moved from one site to the next, a step at a time. This has been

likened to a “bucket row” or human chain, passing buckets of water down a line.

  • As these buckets of electrons reach the end of the line they are dumped out and measured, and this analog measurement is then turned into a digital value.
  • Thus, a digital grid is made which describes the image.
slide68
CCDs
  • CCDs can collect 90% of photons that strike them
  • Photographic plates can only collect 10% of the photons
  • CCDs are split into squares called pixels
  • Data is in electronic form
hubble telescope
Hubble Telescope
  • Can observe in visible, infrared, and ultraviolet wavelength regions
  • Named after Edwin Hubble, the father of modern cosmology
hubble launched in 1990
Hubble (launched in 1990)

Telescope is the

size of a

school bus

2.4 m mirror

initially1
Initially
  • Hubble’s primary mirror was polished to the wrong shape
  • Was too flat at the edges
  • Was barely 2.3 micrometers out from the required shape (1/50 the width of a human hair)
  • Images were not focused as well as they could be
  • Later shuttle mission fixed this problem by installing a number of small mirrors
slide75

http://video.nationalgeographic.com/video/player/science/space-sci/exploration/hubble-sci.htmlhttp://video.nationalgeographic.com/video/player/science/space-sci/exploration/hubble-sci.html

hubble replacement
Hubble replacement
  • The first major components of the new James Webb Space Telescope are now being assembled.
  • While Hubble is the size of a bus, the new James Webb will be the size of a jetliner.
  • Will launch in 2014
  • James Webb is a former NASA administrator during the Apollo program