Astronomy 1020- Test 1- (UGA) Magnani
You are turned to 790 on AM radio. That station broadcasting at a frequency of 790 KHZ (790*10) HZ. You switch to 98.3 on FM radio. That station is broadcasting at a frequesncy of 98.3 (98.3*10^7 HZ).
part A,B,C below...
IRAS
(I)nfra(r)ed (A)stronomy (s)atalite needs to be kept cold with liquid helium launched in 1982.
Spitzer Space Telescope
(Infrared) A large space telescope launched by the U.S. in 2003 and placed into a heliocentric solar orbit, it photographs the sky in Infrared wavelengths. (Only lasts a few years... always leaking)
LIGO
(L)aser (I)nterferometerical (G)ravimetrical- wave (O)bservatory: Gravitational wave detects using lasers and dual detectors. The first thing made to do something Einstein predicted we could do 100 years ago- second most impressive machine we've ever made aside from the large hadich collider.
Part a) What are the wavelengths of the AM and FM radio signals?
(MATH) Answer: FM 3.05 / AM 380m
Chandra
(X-Ray) closed with a bunch of mirrors at angels to catch the rays
3 big break throughs in astronomy....
1) Discovery of the telescope- 17th century 2) Invention of Spectroscopy - 18th to 19th century 3) opened up the entire electromagnetic spectrum- 21st century
What do telescopes do?
1) magnification (less important) 2) Light-gathering - lets you see faint things 3) Resolution- the smallest angel between two points so that you can see them as two points instead of one (ability to see detail)
Optical telescopes
1) refractors- use lenses to gather the light and focus (early 1600's) 2) reflectors- Uses mirrors (late 1600's)
Where are neutrino detectors located? Why are neutrino detectors so difficult to detect?
Neutrino detectors are deep inside mountains, often in abandoned mines. Neutrino only by weak force so interactions between them and baryonic matter are quite rare.
Ground based astronomy
Optical and Radio
A planet with no atmosphere at IAU from the Sun would have an average blackbody surface temperature of 279 K if it absorbed all the SUn electromagnetic energy falling on it... (albedo= 0)
Parts A, B, C below...
electromagnetic spectrum
Radio, infrared, visible (ROY G BIV), Ultra Violet, X-Ray, Gamma
Two stars appear to have the same brightness, but one star is 3 times more distant than the other. How much more luminous is the more distant star?
Star 1 is 9 times more luminous than Star 2
inverse square law of light
If something is 2 times as far away it's only 1/4th as bright.
Effelsberg
100 meter radio telescope in Germany
NRAO
140 foot radio telescope
Part B) What would the average temperature be if its albedo were 0.9, typical of a snow-covered surface?
157 K
Part A) What would the average temperature on the planet be if albedo were 0.1, typical of a rock-covered surface?
272 K
On a dark night, you notice that a distant lightblub happens to have the same brightness as a firm 5 meters away from you. If the lightbulb is a million times more luminous than the firefly, how far away is the lightbulb?
5000 m
SOPHIA
A plane that has an infrared telescope (SOPHIA) 2 major trips per year anywhere from 12-20 per day and runs a couple weeks- in a day that is antivibration chamber
Astronomers describe certain celestial objects as being red-shifted or blue-shifted. What do those terms indicate about the objects?
A red-shifted object is moving away from you; a blue-shifter object is moving toward.
Explain adaptive optics and how they improve a telescope's image quality.
Adaptive optics correct for the blurring produced by the earths atmosphere. This makes the image clearer by improving the resolution.
You observe a spectral line of hydrogen at a wavelength of 502.3 cm in a distant galaxy. The rest wavelength of that line is 486.1 nm. What is the radial velocity of that galaxy? Is it moving toward you or away from you?
Answer: (502.3- 486.1)/ 486.1
Some of the hottest stars known have a blackbody temperature of 100,000 K. What type of radiation is is?
Answer: 29*10^-9 = 29 nm
The Sun has a radius of 6.96* 10^8 and a blackbody temperature of 5780K. Calculate the Sun's Luminosity.
Answer: 3.85* 10^26 J/S
Some people believe that we put astronomical telescopes on high mountain tops or in orbit because doing so gets them closer to the objects they are observing. Explain what is wrong with the popular misconception, and give the actual reason telescopes are located in those places.
Astronomical objects are so far away that moving closer to them by 5 miles makes no difference. However, the higher up you go, the less of the Earth's atmosphere you have to deal with.
If the Sun instantaneously stopped giving off light, what would happen on Earth?
B) Earth would get dark 8 minutes later
Optical telescopes revel much about the nature of astronomical objects. Why do astronomers also need information provided by gamma-ray, x-ray, infrared and radio telescopes?
Becuase different objects emit light in different parts of the electromagnetic spectrum. To really understand what an object is, you need to study it over all the lambda or frequency it is emitting.
Is light a wave or particle or both? Explain your answer.
Both! Light manifests both wave and particle properties. Basically, when you do an experiment designed to test the particle properties of light, light behaves, like a particle. When you do an experiment to test the wave properties and light behaves like a wave.
The Gregorian Feed
Built from 1993 Allows full utilization of reflector surface accuracy - 12 GHZ
November 15th 1988
Collapse of the 300 yard telescope (replacement was the 100 meter green bank telescope)
Part c) What are the photon energies of the two broadcasts?
E(AM): (6.63*10^-34) (7.9*10^5)= 5.2 (10)^-28 J E(FM): (6.63*10^-34) (9.83*10^7)= 6.5 (10)^-26 J
Ewen and Purcell
Ewen was working on completing a doctorate in physics by building a receiver to detect the 21 cm line of neutral hydrogen, supervised by Purcell.
Part b) Which broadcasts at higher frequencies, AM or FM?
FM is the higher frequency
Karl Jansky
Father of radio astronomy
Humans have sent various kinds of spacecraft- including flybys, orbiters and landers- to all planets in our solar system. Explain the advantages and disadvantages of each of those types of spacecraft.
Flybys are the cheapest missions, but they spend very little time studying the objects they are flying by. Orbiters are more expensive, but they can send back hundreds of hours worth of photos. Rovers are the most expensive by far, but they give up close views and can even interact with their immediate environment.
The mini- Gregorian
Tests instrument for Gregorian feed concept. two reflecting surfaces shaped from ray tracings. illuminated a circular aperture with diameter 106 m
Correcting the Spherical Aberration of the Reflector:
The Gregorian feed concept replaces the line feeds with a dual reflector secondary and tertiary which brings radiation from reflector to a point focus.
Green Bank Telescope
The Robert C. Byrd Green Bank Telescope was dedicated in 2000. It is the world's largest fully steerable radio telescope.
Web telescope
The incumbent replacement for Hubble
An object somewhere near you is emitting a pure tone at middle C on the octave scale (262 HZ). You, having perfect pitch, hear the tone as A above middle C (440 HZ). Describe the motion of that object relative to where you are standing.
The received frequency is higher than the emitted frequency. Thus, the object is moving towards you.
(chapter 6, question 3) Matching portion.... a) aperture b) resolution c) focal length d) chromatic aberration e) diffraction f) interferometer g) adaptive optics
_f_ two or more telescopes connected to act as one. _c_ distance from lens to focal plane _a_ diameter _b_ ability to distinguish close objects _g_ computer-controlled correction for atmospheric distortion _d_ color- separating effect _e_ smearing effect due to sharp edge
If one telescope has an aperture of 20 cm, and another has an aperture size is the only difference, then which should you choose, and why?
c) the 30 cm, because the light- gathering power will be better
What is the surface temperature of star that has a peak wavelength of 290nm?
a) 1000K
The light-gathering power of a 4 meter telescope is _____ than that of a 2 meter telescope.
a) 4 times larger
Star A and star B appear equally bright in the sky. Star A is twice as far away from Earth as star B. How do the luminosities of stars A and B compare?
a) Star A is 4 times as luminous as star B
When an electron moves from a higher energy level in an atom to a lower energy level.
a) a photon is emitted
Which of the following can be observed from Earth's surface? (Choose all that apply)
a) radio waves e) visible light
The part of the human eye that acts as the detector is the...
a) retina
When less energy radiates from a planet, its _________ increases until a new ________ is achieved.
a) temp; equilibrium
The advantage of an interferometer is that...
a) the resolution is dramatically improved
How does the speed of light in a medium compare to the speed of light in a vacuum?
c) the speed in the medium is always slower than the speed in a vacuum
Two 10-meter telescopes, separated by 85 meters, can operate as an interferometer. What is its resolution when it observes in the infrared at a wavelength of 2 microns?
b) 0.005 arcsec
If we could increase the quantum efficiency of the human eye, it would
b) allow humans to see better at night or in other low-light conditions
Why is an iorn atom a different element from a sodium atom?
b) an iorn atom has more protons in it's nucleus than a sodium atom has.
The temperature of an object has a specific meaning as it relates to the object's atoms. A high temperature means that the atoms...
b) are moving very fast
Cameras that use adaptive optics provide higher spatial resolution images primarily because
b) deformable mirrors are used to correct the blurring due to earths atmosphere.
As a blackbody becomes hotter, it also becomes __________ and __________.
b) more luminous; buler
Why would astronomers put telescopes in airplanes?
b) to get the telescopes above most of the water vapor in Earth's atmosphere
Refraction is caused by...
c) light changing speed as it enters a new medium
Improved resolutions is helpful to astronomers because...
d) all of the above
The angular resolution of a ground-based telescope is usually determined by...
d) diffraction
Arrays of radio telescopes can provide much better resolution than single-dish telescopes can because they work based on the principle of....
d) interference
When a boat moves through the water, the waves in front of the boat bunch up, where waves behind the boat spread out. This is an example of?
d) the doppler effect
If a planet is in thermal equilibrium,
d) the temperature is very low
Two stars are of equal luminosity. Star A is 3 times as far from you as Star B. Star A appears ________ Star B.
e) 1/9th as bright
Magnification formula
focal length of objective / focal length of eyepiece
Emitting light
going down on the (quantum) energy levels
Absorbing light
going up on the (quantum) energy levels
Blackbody
idealized perfect absorber of all incident electromagnetic radiation; such bodies emit electromagnetic radiation in characteristic continuous spectra called blackbody radiation
Frequency and wavelength are _______ related
inversely
What is the biggest thing holding back Astrophysics?
money
Super-Kamiokande Neutrino Observatory
neutrino detectors 1/2 mile underground with photo cells covering the surface.
magnification does nothing for....
resolution
Multi-messenger astronomy
~ 90% via EM spectrum neutrinos cosmic rays - charged particles (electrons, protons, helium nuclei...)
