Astronomy Fall 2013 Final Exam

History of Astronomy1. Know: speed of light, astronomical unit, and light year.

Extremely fast (nothing else can travel as fast as light) 3.0 x 108 m/s. 1 a. u. is the distance from earth to the sun. Distance (not time!!) that light travels in 1 year.

2. Explain red shift and blue shift. What do they determine about motion?Dopler effect from a moving object giving off light; red wavelenths are longer so the light is stretched meaning the object is moving awayfrom the observer. Blue wavelengths are shortened so the object is moving towards the observer (coming at you)

3. What is the difference between apparent and absolute luminosity?Absolute is the true actual brightness of the star. Apparent is how bright the star appears to us from earth in our night sky.

4. What is a star chart and how is it used?Shows the constellations in the night sky; it rotates for the time/month of year. Used to find constellations in the night sky.

5. Sketch an astrolabe. Describe how to use an astrolabe to determine latitude. Why can’t an astrolabe measure longitude?

Match the face plate of the marking on the surface of the disk with certain stars in the night sky and align the bar to determine your longitude (side to side direction). Because to find longitude you would need a tool that measures 3D.

6. Who is credited with inventing the first telescope? When? Give two ways this tool helps to overcome difficulties of studying astronomy (how did this help).

Galileo- 1609; THE PURPOSE OF THE TELESCOPE IS TO GATHER LIGHT NOT TO MAGNIFY NOT A MICROSCOPE!! It focuses objects (resolving power) divides blurry objects. Allows us to see further and distance is huge difficulty in astronomy. (especially Hubble).

7. What are the two main types of telescopes? How do they work. List 1 good and 1 bad thing for each. REFLECTIVE (MIRRORS) BIGGER AND BETTER AND THEY DO NOT DISTORT THE IMAGE BECAUSE THEY REFLECT. BAD: THEY CAN FOG SO WE PUT RADIOACTIVE ISOTOPES TO RELEASE HEAT INSIDE THE PROBE WHEN WE SEND IT IN TO SPACE AND KEEP THE MIRROR FROM FOGGING;

REFRACTIVE (LENS) DISTORTS IMAGE WHEN LIGHT BENDS THROUGH THE LENS. 1 GOOD THING= SMALLER SO THEY ARE CHEAPER

8. Why are most ground telescopes built on mountains? What type of telescope are all large ground telescopes? TO CUT DOWN ON ATMOSPHERIC BLURRING. THEY ARE REFLECTIVE TELESCOPES= BIGGER

9. When looking into the Hubble Space Telescope you are looking back in history, if the galaxy is 2 million light years away, then you are looking back in time to ___2 MILLION _______ years ago.

10. The correct order of the listed structures from smallest to largest is:

a. solar system, galaxy, local group, universe, planet

b. planet, solar system, galaxy, local group, universe

c. planet, universe, solar system, galaxy, local group

d. galaxy, local group, universe, planet, solar system

11. What is the word for the belief that the Earth is the center of the whole universe and everything revolves around Earth? Geocentric

12. What is heliocentric? And is this correct? The theory that everything in the solar system revolves around the Sun. YES!

13. Keppler discovered planets orbit a star in what shape? ? ELLIPTICAL (ELIPSE)14. Know the planets of our solar system in order. SUN: MERCURY, VENUS, EARTH, MARS,

(ASTEROID BELT) JUPITER, SATURN, URANUS, NEPTUNE, (KEPPLER BELT)

15.___D___ 21. Tycho Brahe (1546 – 1601) a) Developed the Law of universal Grav-

itation and 3 laws of forces.

___A___22. Newton (1642 – 1727) b) Invented the telescope in 1609. (He was banned by the Roman Catholic Church)

___B___ 23. Galileo (1564 – 1642) c) Understood that the earth is not the center of the universe and laid out the order and relative motion of the known solar system

___C___ 24. Copernicus (1473 – 1543) d) His observations of planetary motion with great accuracy proved circular or-bits could not work.

___E___ 25. Eratosthenes (276 – 194 B.C.)

e) In 200 B.C. used simple geometric reasoning to calculate the size of the earth. (using shadows)

16. List all the phases of the moon, sketch each:NEW MOON, WAXING CRESCENT, FIRST QUARTER MOON, WAXING GIBBOUS, FULL MOON,

WANING GIBBOUS, LAST QUARTER (4TH) MOON, WANING CRESCENT

The Sun & Stars

1. The light we see from the Sun comes from which layer? Photosphere; a pin hole camera (looking at a reflection and not directly at the sun.

2.The density of the Sun is most similar to what object? Jupiter

3.What process gives the Sun, and all stars, their energy? Nuclear fusion of hydrogen

4.The solar constant is a measure of _Sun’s energy that reaches earth over a 1 m2 area____.

5.The luminosity of the Sun is a measure of _total output of energy from the sun in all directions.

6.Solar energy reaches the Sun's photosphere by __convection zone_____, from the layer justunderneath it.

7.Hydrostatic equilibrium in our Sun is the balance between __inward gravity = outward pressure

8.The vibrations of the Sun reveal information about the _doppler shifts (red away; blue toward).

9.What does the diagram below indicate? The core of the sun is hottest (15 million K) as you get further away from the core the temperature decreases.

10. What is happening in the core that makes it so hot? What temperature in Kelvin is needed to achieve this? Nuclear fusion of hydrogen. 10 million K

11. A loop of gas following the magnetic field lines between sunspots' poles is a _prominence__.

12. How long does the sunspot cycle last, on average? 11 years and north and south flip for another 11 years so 22 total.

13. What are the characteristics of sunspots? Slightly cooler than its’ surroundings; always in pairs.

14. What are the two most important intrinsic properties used to classify stars? Surface temp. and luminosity

15. What physical property of a star does the spectral type measure? Composition of elements/Surface temp.

16. The star's color index is a quick way of determining its: surface temp.

17. The most famous G type star is _the Sun__.

18.On the H-R diagram, the Sun lies _middle of main sequence (luminosity of 1 and G type)__.

19.What stage do stars spend the majority of their lives in? main sequence

20.On the H-R diagram, red supergiants lie __top right side above main sequence_.

21.On the H-R diagram, white dwarfs lie _bottom left__.

22.In what range of masses are most stars found?

23.What is the single most important characteristic in determining the course of a star'sevolution? MASS

Match the constellation to the correct star.

24.Ophiuchus D

25.Orion A

26.Taurus E

27.Ursa Minor C

28.Canis Majoris F

29.Draco B

30. The __absolute__ magnitude of a star depends directly upon its luminosity anddistance.

31.From hottest to coolest, the seven letters for the star types are OBAFGKM______________.

32.The bigger and brighter a cepheid variable star, the _SLOWER (Longer periods)_it will pulsate.

33.__DISTANCE_____________ is the single greatest frustration in all of astronomy.

34.Originally there were __88___ constellations.

Stellar Formation and Evolution

1.What makes the subject of star formation so difficult and complex? FAR AWAY, LAST A REALLY LONG TIME

2.Our Sun, along with most of the stars in our neighborhood formed about _5 BILLION YEARS AGO_.

3.What is the force that keeps a main sequence star from blowing apart? HYDROSTATIC EQUILIBRIUM- GRAVITY

4.What event marks the birth of a star? FRAGMENTS OF DUST AND GAS COLLECTING TOGETHER. WHEN NUCLEAR FUSION OF HYDROGEN (10 MILLION K) IT IS A STAR

5.What happens when an interstellar cloud fragment shrinks? FORMS A PROTOSTAR AND STARTS STELLAR FORMATION

6. What is the force that keeps a main sequence star from collapsing on itself? OUTWARD PRESSURE FROM HOT GAS EXPANDING

7. The single most important determinant of the temperature, density, radius,

A. Betelgeuse

B. Thuban

C. Polaris

D. Barnard’s star

E. Aldebaran

F. Sirius

luminosity, and pace of evolution of a protostar is its _ MASS __.

8. A cloud fragment too small to form a star becomes _ BROWN DWARF (FAILED STAR)__.

9. What is characteristic of globular star clusters? CIRCULAR SMOOTH SHAPE (OLD NEBULAE)

10. What are the characteristics of an open cluster of stars? NO EDGES/ SHAPE (YOUNG NEBULAE)

11. What is the most important fact about a cluster of stars that makes them useful forstudying star formation?

12. A star (no matter what its mass) spends most of its life: IN THE MAIN SEQUENCE

13. When a star's inward gravity and outward pressure are balanced, the star is said tobe __ HYDROSTATIC EQUILIBRIUM __.

14. What are the elements contained in your body that formed in the cores of starsDuring thermonuclear fusion? MOSTLY CARBON, OXYGEN, AND NITROGEN. BUT ALL

ELEMENTS ON THE PERIODIC TABLE ARE FORMED THERE DUE TO NUCLEAR FUSION

15. The order of evolutionary stages of a star like the Sun would be Main Sequence,giant, planetary nebula, and finally __ White Dwarf __.

16.Compared to our Sun, a typical white dwarf has __less__ mass.

17.What are the future stellar stages for our Sun? Red Giant and White Dwarf

18. The most famous case of a more massive hot star orbiting with a more evolved butpresently less massive red giant is the eclipsing binary ___.

Match word with the picture or statement. Draw linesa. emission nebula

b. open cluster

c. contact binary

d. hydrogen brown dwarf

e. supernova

f. Orion nebula

g. planetary nebula

h. globular cluster

i. carbon-oxygen white dwarf

j. neon-oxygen white dwarf

k.

l. helium white dwarf

Stellar Explosions

1. An iron core cannot support a star because no more fusion can occur

2. Beyond the formation of iron, nuclear energy can be produced only by fission and fusing heavy elements

3. A neutron star is ___ A really really dense core that remained after a type 2 supernova explosion___.

4.Where was supernova 1987a located? Large Maganellic cloud in a near by galaxy

5. What produces a Type I supernova? Binary star system with a massive star (8 – 12 solar masses) and white dwarf collide

6.What is the Lighthouse model for pulsating stars? A spinning neutron star shooting a beam of light on earth you see a flash of light like a light house.

7. What produces a Type II supernova? Supermassive (greater than 12 solar masses) cloud starts fusing elements until it makes an iron core- then it recoils and explodes

8.Almost half of all known millisecond pulsars are found in what type of object?

9. What is the critical difference between millisecond and normal pulsars.

10. What explanation does general relativity provide for gravity?

11.If light from a distant star passes close to a massive body, the light beam will _Bend____.

12.What is Cygnus X-1? Stellar mass black hole (smaller than Sag. A) in the Milky Way galaxy inside the constellation Cygnus (the Swan).

13.Super massive black holes are ___ More than 12 solar masses __ solar masses.

14. What is the supermassive black hole at the center of our galaxy called? Sagittarius A (3.7 million solar masses)

The Milky Way and Galaxies

1.In structure, our Milky Way is most similar to _Andromeda Galaxy_____.

2.The part of the Milky Way we are most familiar with is the _Galactic Disk____.

3. The first attempt to map the Galaxy via star counts was done by: 18th Century astronomer William Herschel

4. Why was Herschel's strategy for mapping our Galaxy flawed? Because the majority of the galactic disk is blocked by gas and dust so he couldn’t see enough to make an accurate map. He needed infrared vision.

5. The RR Lyrae stars all have periods of _0.5 to 1 day_____.

6. Both RR Lyrae and Cepheid variable stars are stars that, when on the mainsequence, were considered to be _intrinsic variable_____.

7.What is one of the differences between Cepheids and RR Lyrae variables? Cepheids have a stronger period luminosity correlation and they have much longer pulsation periods (up to 100 days).

8.The region on the H-R diagram where pulsating variables occur is called the _instability strip____.

9.Most of the new star formation in the Galaxy is found in the _galactic disk____.

10.Name the types of objects found in the Galactic Halo? Old stars Globular clusters, no gas and dust, no stellar birth in the last 10 billion years, reddish in color, population 2 stars.

11. What is a Galactic Year? How long is our galaxy’s Galactic Year? The orbital period of the Sun around the Milky Way galaxy’s galactic center. It takes 225 million years

12.What is our Sun's location in the Galaxy? About ½ way from the galactic center and the end of the galactic disk; it lies along the galactic disk in the spiral arms.

13.What objects are found in the Galaxy's spiral arms? Young stars, supernova explosions, planetary nebulae, open clusters, our Sun,

14.From Earth, the view of the Milky Way is a thin band of stars across the night sky.The part of the Milky Way galaxy that is described here is the _galactic disk____.

15.Star formation ceased first in the _halo____.

16.Density waves may explain _formation of spiral arms____.

17.What observations suggest the mass of the Galaxy goes much farther out than itsvisible disc? Galaxy Rotation Curve (see graph on last page)

19.Most of the mass of the Milky Way seems to exist in the form of _dark matter____.

20.What two observations allow us to calculate the Galaxy's mass? The Sun’s orbital size (distance of the Sun to the galactic center) and orbital period.

21.Detailed measurements of the disk and central bulge region of our Galaxy suggestour Milky Way is a _Barred Spiral____.

22.From the Sun, the distance to the Galactic Center is about 8 kpc_____.

23.For what type of object is the period-luminosity relation used for determiningdistances? Cepheids

24.The first Cepheid variable star was found in the constellation ___Cepheus_____.

25.RR Lyrae and Cepheid variables are ___intrinsic_______ variables.

26.The Galactic Bulge is shaped like a ___football_________.

27.The formation of the Milky Way Galaxy is similar to the formation of __our solar system_______.

28. The structure of the Milky Way Galaxy is similar to what other galaxy? Andromeda Galaxy

29.The first RR Lyrae variable star was found in the constellation __Lyra (HARP)_________.

30.What variable star does the graph below represent? ____RR Lyrae__________________

31. What variable star does the graph below represent? __Cepheids____________________

32. What variable star is indicated by the diagonal line below? ______Cepheids__________

33. What variable star is indicated by the box ? _RR Lyrae_________________

34. What variable star occupies the region of the H-R Diagram below? __________

35. What variable star occupies the region of the H-R Diagram ?___________

36. What is the object in the circle below?________________

Identify each Object:

40. Object 4 D

41. Object 2 C

42. Object 1 B

43. Object 5 A

44. Object 3 E

48.The Milky Way is often considered to be an intermediately wound, barred spiral, which would be type ___Sa_____ according to Hubble.

A. Globular clusters

B. Galactic halo

C. Galactic bulge

D. Galactic disk

E. Galactic center