1. Prepare your scantron:
Use
a pencil,
not a pen!
Fill in your name and fill the bubbles under
your name.
LAST NAME FIRST, First name second
Put your 4-digit code instead of “IDENTIFICATION NUMBER”.
--- (The last 4 digits of your OleMiss ID.)
Question # 1: answer A
Question # 2: answer C
Question # 3: answer C
Setup:
Test 2 on Wednesday!
Please take a moment to mute your cell phone!

2. Review questions coming …

3. This question counts double!
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Question 4
The unit of seeing is …
A magnitudes.
B light years.
C arc seconds.
D parsecs.
E nothing: seeing is a number without units.
Next question coming …

4. This question counts double!
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Question 5
The most important purpose of a telescope is …
A bring far-away object closer.
B to magnify the view by thousands of times.
C to break up the light into colors.
D to make dim object brighter.
E to screen out damaging radiation from starlight.
Next question coming …

5. This question counts double!
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Question 6
What is the magnification of a 12-inch telescope,
120-inch focal length, when a 1-inch eyepiece is used?
A 10 times.
B 12 times.
D 120 times.
E 2.5 magnitudes.
Next question coming …

6. This question counts double!
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Question 7
How large is the smallest crater a good telescope can resolve on the Moon?
A A foot.
B A mile.
C A hundred miles.
D Two thousand miles.
E No crater is visible on the moon with a telescope, only spacecraft images can show them.

7. The professional way of doing astronomy: picture taking and imaging
Visual vs. CCD
(1) Visual observation: always unreliable
Recall the canals on Mars - G. Schiaparelli &P. Lowell

8. The professional way of doing astronomy: picture taking and imaging
CCD
(2) Photography: • reliable • can collect light for a long time
(3) The modern way: CCD imaging
• in CCD chip light moves electrons into pixel
• computer counts electrons in each pixel
and turns numbers into image on screen
Similar to a digital camera but:
• chip is cooled to reduce noise
• computer controlled - image can be much
improved with computerized processing techniques
• many images can be added to improve quality
The CCD revolution after 1995: one can take pictures
even of galaxies with amateur equipment from light-polluted sites.

9. The Helix - a planetary nebula (amateur CCD image)
Helix CCD

10. incredible resolution:
Helix HST
The Helix
A Hubble telescope
CCD image
incredible resolution:
16,000 x 16,000

11. Questions coming …

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Question 8
Why do astronomers no longer look into
their telescopes?
A Because the observer’s body would obstruct the
light in research-grade telescopes.
B Because visual observations are unreliable.
C Because there is dangerous radiation in a research observatory.
D Because large telescopes collect so much light that their eyes
would be damaged.
E Because there is nothing left to discover in optical light;
infrared and X-ray radiation must be observed to make new
discoveries.
Next question coming …

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Question 9
What is a CCD?
A A new type of telescope that replaces reflectors.
B A new type of optical device that replaces the lens or mirror
of a telescope.
C A new type of a telescope mount.
D A new type of a detector that replaces photography.
E A new type of an instrument that separates colors in starlight.
Next question coming …

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Question 10
Which of the following is an advantage of
photography over visual observations in astronomy?
A Film has better resolution than the human eye.
B Film can photograph X-rays, while the human eye
cannot see them.
C Film can collect light for a long time.
D Film can be handled automatically in observatories in remote
high mountains.
E Seeing does not affect film photography.

15. Radio telescopes
Advantage: can see radiation from charged particles flying
in magnetic field between stars.
Trouble: needs huge antennas for resolution and sensitivity
Jodrell Bank Radio Observatory
Interferometry:
several antennas to work together
improves resolution
but does not help lack of ‘light’

16. X-ray astronomy - Chandra
Launched: 1999
X-ray sources:
when energetic charged
particles hit magnetic fields
• Supernova explosions
• Supernova remnants
• Black holes in nuclei of active galaxies
• Glow of intergalactic gas

17. Infrared astronomy - Spitzer
Launched: 2003 on solar orbit
Infrared sources:
not-so-hot objects
Infrared light is not absorbed
by interstellar dust as regular
light is: can see through
• Newly forming stars and their protoplanetary dust disks
• The center of the Galaxy (behind dust)
• Interstellar dust glows ( K)
• Small and not-so-hot stars ( K)

18. Centaurus A Centaurus A - an active galaxy at various wavelengths
Optical and radio
X-ray (Chandra)
IR (Spitzer)
Optical: starlight and dust obstruction
Radio: charged particle jets in magnetic field
X-ray: very energetic charged particle jets
in magnetic field
Infrared: cold (~100K) dust glows

19. Questions coming …

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Question 11
Name an object that we can see in infrared but not in regular light.
A The Sun.
B A supernova.
C A hot star.
D The center of the Galaxy.
E An asteroid.
Next question coming …

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Question 12
In what wavelength can we see
newly born stars best?
A Radio.
B Infrared.
C Optical.
D X-ray.
E Ultraviolet.
Next question coming …

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Question 13
What objects can radio telescopes study most efficiently?
A The Moon.
B Interstellar matter.
C Stars.
D Comets.
E The planets.
Next question coming …

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Question 14
Why do we need to place X-ray telescopes on spaceships?
A Because there is too much disturbing background
X-ray radiation on Earth.
B Because X-ray detectors must be cooled to the
temperature of space.
C Because X-rays get absorbed in the atmosphere.
D Because the gravity of Earth repels X-rays from celestial objects.
E Because we must get the X-ray detectors closer to the stars.