EXAM REVIEW – NATS

Chapter Eight

1. What was William Herschel looking for when he discovered Uranus? What made Herschel particularly suited for discovering planets? In what 2 ways did Uranus reveal itself to Herschel as a planet? What is it about Uranus' orbit that caused it to be considered a planet instead of a comet? What is the origin of Uranus' name?

He was looking for Stellar ParallaxHe was well suited because he built the biggest telescopes of his timeWay 1: it increased in size when he increased the telescope’s magnificationWay 2: it had a near-circular orbit. It was not eccentric, it was elliptical. Greek god of the sky.

2. What did Kepler believe existed between the large space between Mars and Jupiter? Explain why Bode's Law supported this idea.

He believed it contained an unknown planet. Bode’s law supported this idea because planetary distances follow a numeric sequence. Uranus followed this sequence as well.

3. What is the name of the object found in 1801 between Mars and Jupiter? What was this object finally classified as, and why? What is this object a part of?

It was a star-like object with a near – circular orbit. It was smaller than the moon so it was downgraded as an asteroid. Object was a part of an asteroid belt.

4. What caused Adams and Leverrier to suspect the existence of a planet beyond Uranus? When this planet was found, what was it named, and why?

There were deviations in Uranus’ orbit. It was named Neptune, roman god of the sea because of its bluish colour.

5. How were the masses of Uranus and Neptune 1st measured? How do their masses compare with the other planets? Based on the masses and sizes, what do we know about their densities and compositions?

They were first measured by using the orbits of the planet’s moons. They are compared in relative to Earth, and are bigger. Therefore they are gas giants.

6. What is today's theory for why all the planets in our solar system orbit the Sun in the same direction and in roughly the same plane? What is the observational evidence for this theory?\

after the Sun was born from a spinning, collapsing gas cloud, the remaining gaseous and rocky particles in the Sun's spinning circumstellar disk coalesced into planetsdisks of matter have been found around newborn stars in star-forming nebulae

7. What is today's theory for the asteroid belt? What about planetary rings?

Asteroid belt: likely the leftover debris from the Sun's circumstellar disk that couldn't coalesce into a planet due to the opposing gravitational pulls of the Sun and nearby giant Jupiter Planetary rings: planetary rings are likely leftover debris from protoplanetary disks which couldn't coalesce into a moon

8. What 3 attributes are unique to the 4 planets beyond Mars? What is the current explanation for this?

Gas giants, numerous moons, and have rings. This is because the outer circumstellar disk contained more material, allowing the outer planets to collect more mass and to attract more debris into orbit as moons and rings

9. Which planets are the terrestrial planets? What is the current explanation for their lack of gas?

Mercury, venus, earth, mars. This is because the planets’ solid cores were likely the first to form. Since the outer planets grew faster, they had ore gravity to draw in the gas particles, leaving the inner planets with much less gas .

10. What is the current theory for the origin of Mars' two moons? What is the evidence to support this theory?

Mars' 2 moons appear non-active to Mars (both look like asteroids and one is retrograde)

11. Why is it unusual for Earth to have such a large moon? What is the current theory for the origin of Earth's moon?

the large size and composition of Earth's one moon suggests that it came from a large Earth impact

12. What belief about Mars was popularized by Percival Lowell, and why? Was he right?

lowell believed that intelligent life exists on mars, cuz he thought he saw martian-made canals on the planet's surface. he was wrong.

13. Why was there suspected to be a planet beyond Neptune?

initial underestimate of Neptune's mass led to the theory that an additional planet is perturbing Uranus' orbit

14. When Lowell's predicted planet was finally detected, what was it named, who named it, and why did she choose this name?

planet was named "Pluto" (Greek god of the Underworld) by a young girl from England because it was dark.

15. Why did the discovery of Pluto turn out to be a coincidence?

the discovery of Charon (largest of Pluto's three moons) revealed Pluto's mass (0.002 x Earth, too small to perturb Uranus; Pluto was the amazing shrinking planet). Pluto's discovery was therefore a coincidence

16. The discovery of what kind of objects motivated the IAU to define the conditions for being a planet? Where are these objects? What was the significance of the object now known as Eris?

Disks of icy debris around the planets motivated the IAU to define the conditions for being a planet. These objects are dwarf planets. Eris was the 1st KBO (Kuiper Belt Objects) discovered with a mass greater than Pluto's. It motivated the IAU to define what it means to be a planet.

17. What are the IAU's planet conditions? Which condition(s) does Pluto fail? What condition(s) do comets fail? What condition(s) do asteroids fail?

Conditions:- it must be in solar orbit (orbit around the sun) (exclude moons)- it must be a sphere by its own gravity (excludes comets and some asteroid)- it must have cleared the debris around its orbit (excludes all asteroid and KBOs)Pluto failed criterion #3 and is now considered a dwarf planet (an object which only meets the first two criteria for a planet)Comets fail #2Asteroids fail #3

18. What is Pluto now considered? What are the condition(s) for this type of object? Is this type of object expected to be common in our solar system?

pluto is a dwarf planet. the conditions are #1 and #2 from the IAU's planet definition. dwarf planets are expected to be common.

Chapter Nine

1. Why did all attempts to detect stellar parallax fail until the 1830s?

there were many failed attempts to detect stellar parallax, owing to the incorrect assumption that the brightest stars are the nearest stars

2. What did Halley announce about stars in the early 1700s? How did this discovery aid the detection of stellar parallax? 

Halley compared ancient star catalogues with current star positions and found three moving stars. Now that they move, it is known that brightest stars aren’t always the nearest.

3. What is our nearest star, and how far away is it (approximately) in light years? 

Alpha Centauri is the nearest star and has a distance of 4.4 ly,

4. What is the definition of a light year? What is the definition of a parsec? (NOTE: the specific values in km aren't necessary here). Which unit is bigger, and by approximately how much?

Distance light travels in a yearthe distance of an object with a parallax of 1 arcsecond.Parsec is bigger by a third. 1pc = 3ly

5. According to the wave theory of light, what are all light waves composed of?

Wave of oscillating electric and magnetic fields

6. Describe how a wave from a bright blue light source is different from a wave from a faint red light source. 

?

7. What colour of visible light is shortest in wavelength? What colour of visible light is longest in wavelength? What colour of visible light has the lowest frequency? What colour of visible light has the most energy?

Blue is shortestRed is longestRed has lowest frequencyBlue has most energy

8. In the full spectrum of light, what kind of light is shortest in wavelength? What kind of light is longest in wavelength? What kind of light has the most energy? 

Ultraviolet is shortest Red is the longestUltraviolet has the most energy

9. What is a spectroscope? 

Fraunhofer passed sunlight through glass and observed the spectrum through a telescope (a spectroscope)

10. What is Fraunhofer’s Spectrum a spectrum of? What does it contain (ie., continuum emission, absorption lines, and/or emission lines)?

he saw approx. 600 thin dark lines and labeled them with letters to designate their wavelength (Fraunhofer's spectrum)Contained absorption lines, and emission lines

11. Describe (briefly) how the chemical composition of a star can be determined. 

you take a star's spectrum and u match up its absorption lines with the wavelengths of emission lines in the spectra of known substances.

12. What did Bunsen and Kirchhoff observe in the spectrum of sunlight combined with a gas flame? What was their correct explanation for this, and what did it cause them to predict about the Sun? How was their prediction proven in the 1860s?

Bunsen and Kirchoff observed that after a spectrum of sunlight passed through a gas flame the dark lines got thicker. Their explanation for this was that the suns core, which produces the full spectrum of light, is surrounded by a gas layer (an atmosphere). Prediction proven by observing emission lines in the spectrum of the Sun's atmosphere during a solar eclipse

13. How did the element Helium get its name? 

Helium gets its name from Helios, the Greek god of the sun.

14. In a graphical spectrum, what do emission lines appear as? What do absorption lines appear as?

Emission lines: Bright LinesAbsorption Lines: Black Lines

15. What does the spectrum of a star contain (ie., continuum emission, absorption lines, and/or

emission lines)? How about the spectra of a gas cloud, a star cluster, and a gas/star system?

Star: continuum and absorptionGas cloud: emissionStar cluster: continuum emission, absorption lines, and emission linesGas/star system: continuum emission, absorption lines, and emission lines

16. Why was the element Oxygen originally named "Nebulium"?

Because it was found in a planetary nebula

17. What does the spectrum of a planetary nebula contain (ie., continuum emission, absorption lines, and/or emission lines)? When Huggins discovered this, what did it prove about planetary nebulae (ie., what are they made of)?

Emission lines. Proved they are made of oxygen.

18. What is radial motion? How does it effect light waves? What is the name of this effect?

radial motion is motion towards or away from the observer. recessional motion causes light waves to compress (blue shift) and receding motion causes light waves to strech (redshift). this is the doppler effect.

19. How does a light source's spectral lines reveal that the spectrum is redshifted? How about blueshifted? If a spectrum is redshifted, what does this tell us about the motion of the light source? How about if the spectrum is blueshifted?

if the spectral lines (absorption or emission) of a light source are at wavelengths that are either longer (redder) or shorter (bluer) than they are for a light source at rest, then the light source is redshifted or blueshifted. redshift = a receding light source, blueshift = an approaching light source

20. What is astrophotography? Why does it allow us to see deeper into space than with the eye and telescope alone? Who was one of the pioneers of this? What sort of survey did he conduct?

the production of long-exposure sky photos using a camera attached to a telescope. They are long exposure. Henry Draper was a pioneer of it. Conducted a photographic spectroscopic survey of all visible stars

21. What were the members of "Pickering's Harem" hired to do? 

They were hired to complete the Henry Draper Catalogue of spectra of over 225,000 stars

22. What property of stars was used to place the spectral types in their original alphabetical order? What property of stars was used to re-arrange their order into their current order (O-B-A-F-G-K-M)? 

Strength of their Hydrogen lines was originally used, then changed to a star's color

23. What do we know about the chemical composition of the reddest stars, due to their numerous spectral lines? 

Reddest stars have more metals than other spectral types

24. If a star has a spectral type of B8, which type of star is it more similar to, O or A? 

A

25. What is a photon? 

A photon is a particle of light

26. According to the Bohr model of the atom, what are the 3 components of an atom? What determines an atom's chemical element? 

Protons, neutrons and electrons. the # of protons determines the chemical element.

27. Explain (briefly) what causes atoms to produce absorption lines. What about emission lines? 

when an electron absorbs a photon with the exact energy or wavelength it needs to get excited, electrons jump to a higher shell, causing an absorption line.when an excited electron drops down a shell, it emits a photon with the exact energy or wavelength to return to ground state, causing an emission line.

28. What unusual discovery did Cecilia Payne make about the chemical composition of stars? 

All stars are predominantly composed of H and He

29. Describe how Eddington proved one of the predictions of Einstein's General Relativity theory. 

During a total solar eclipse, he proved GR by observing that when light rays pass near the Sun, their path is bent by the curved space around the Sun

30. What was Eddington and Bethe's correct explanation for the energy source of stars? Why does this process release energy? How does it explain why stars produce so much energy? How does it explain the existence of Helium in stars? How does it explain the full spectrum of light that we receive from stars? How does it explain the long lifetimes of stars? 

the energy from stars is produced from the fusion of Hydrogen nuclei into Helium at high temperatures: Nuclearfusion.You lose mass.H-atoms are plentiful in stars the gamma ray downgrade to other wavelengths as they interact with atoms in the airthe initial fusion reaction of Hydrogen takes a billion years

31. At what rate does light dim with distance? 

light dims with distance according to the inverse-square law (i.e. The amount of light we recieve from a source is 1/d2 of its actual light production

32. What is the difference between the apparent brightness and the intrinsic brightness of a light source? 

The short answer - apparent brightness is what we SEE, while intrinsic brightness is the TRUE power of a light source.

33. Which appears brighter, a star with an apparent magnitude of 2 or a star with an apparent magnitude of -2? 

-2

34. For a group of stars in the same star cluster (i.e. at the same distance from Earth), how can we tell which stars are the most luminous? 

Depends on their spectral type (O stars are most luminous, M stars are least

35. What relationship among Main Sequence stars was found by Hertzsprung & Russell in the 1910s? What two kinds of stars were found to not follow this relationship? 

the apparent magnitudes reflected the stars' relative luminosities A and M stars – Red Giants, White Dwarfs.

36. What is the spectral type of the Sun? 

Spectral type refers to O-B-A-F-G-K-M. The Sun is a G star.

37. Using the HR diagram, compare the luminosity, temperature, colour, and size of Red Giants to the Sun. 

Red Giants are 106 as luminous as the sun, they are like 2000K less than the Sun, but they are bigger than the sun.

38. Describe the mass and size of a White Dwarf. Using the HR diagram, compare their luminosity, temperature, and colour to the Sun. 

They are very small, but their mass is also small. Everything is less.

39. What relationship among Main Sequence stars was found by Eddington in the 1920s? What 2 things did this discovery tell us about the Sun? 

The more luminous a star, the higher its massThe sun is a low mass star, the most common kind

40. Compare the luminosity, temperature, colour, size and mass of a Main Sequence O star to a Main Sequence M star. 

Main Sequence OTemp: HotColour: BlueSize: BigMass: Big

Main Sequence MTemp: ColdColour: RedSize: SmallMass: Small

41. What determines a star's spectral type on the Main Sequence? How do we know that a star's Main Sequence spectral type can't change? 

spectral type is set by a star's mass. spectral type can't change cuz that would require a main sequence star to increase in mass and luminosity at the same time, which violates the law of conservation of mass and energy.

42. What was Hoyle's correct explanation for the existence of elements heavier than Helium in stars? How do these elements get on to planets like ours?

elements heavier than helium are posted by nucleosynthesis in stars (ie fusion of the produces of hydrogen-fusion). when massive stars die, they explode, ejecting their heavy elements into gas clouds in interstellar space. the gas clouds collapse into new solar systems like ours - solar systems with planets which contain heavy elements.

43. How do we know that our solar system must have come from the ejecta of other stars? 

44. When a star is on the Main Sequence, what allows its properties to remain stable? 

when a star is on the main seq, it is fusing hydrogen. during hydrogen fusion, a star's radiation pressure equals its gravitational pressure, so the star remains stable. This ends when the star runs out of hydrogen, at which point it leaves the main seq cuz its properties change.

45. What causes stars to leave the Main Sequence? 

Stars leave the main sequence when they run out of hydrogen.

46. Why do we find more low-mass Main Sequence stars than high-mass ones? 

low mass stars take longer to fuse hydrogen but high mass stars fuse faster, so they leave the sequence fast

47. Describe what will happen to our Sun from the time it leaves the Main Sequence to its ultimate corpse. Include how its luminosity, temperature, colour and size will change as it evolves, and how these changes are due to the shifting in the balance between gravity and radiation pressure. 

when H runs out, stars fuse their He. He fusion produces more energy, which causes RP > GP. The star expands, brightens, cools and reddens into a Red Giant when He runs out, low mass stars are too cold to fuse He-products. This causes RP < GP. The core shrinks into a dense, hot, low luminosity corpse (a White Dwarf), while the outer layers shed into a Planetary Nebula

48. What kinds of stars are able to fuse elements heavier than Helium, and why? 

high mass stars are hot enough to fuse He-products into higher elements up to Iron because they have not burned out yet.

49. Describe what will happen to an O-star from the time it leaves the Main Sequence to its ultimate corpse. Include how its luminosity, temperature, colour and size will change as it evolves, and how these changes are due to the shifting in the balance between gravity and radiation pressure.

O, B (RP > GP) Red Giant (RP << GP) Supernova Neutron Star Black hole.

Chapter Ten

1. What is the "Island Universe" theory?

The island universe theory is the theory that our galaxy is just one among billions of other

galaxies in the Universe (no longer a theory - this is now known to be true)

2. Why did the Ancient Greeks use the word "galaxy" to describe the bright strip of light across the sky? What do we call this strip of light today? What part of our galaxy does this strip represent?

Greek: Milky.Us: Milky WayRepresent: Our view through the disk’s length.

3. What did William, Caroline and John Herschel produce together? What was Herschel attempting to prove from this research? Why was he not able to prove this?

Giant Telescopes. They attempted to identify whether nebulae are distant star systems or nearby glowing gas cloudsOwing to the large variety of nebulae, the Herschels couldn't come to a general conclusion about their composition

4. What did Herschel's map of the visible stars reveal about the shape of our galaxy?

It was disk-shaped.

5. What did Lord Rosse discover when he looked at the elliptical-shaped nebulae through his Leviathan telescope?

6. What is a variable star? What characterizes the Cepheid variables? Explain briefly why Cepheids pulsate.

Variable star: star which fluctuate in brightness at regular time intervalsCepheids: has a lightly opaque surface - its outwards photons push the surface outwards, which temporarily expands the star and reduces its opacity

7. What are the SMC and LMC? What did Henrietta Leavitt discover when she observed Cepheids in the SMC? Why was this discovery so valuable? Who used her discovery to determine the boundaries of our galaxy?

The smc and lmc are our nearest galaxies (they stand for Small and Large Magellanic Cloud). Leavitt discovered the period-luminosity relation for cepheids in the SMC (ie, the longer the period, the more luminous the cepheid). Why valuable? because this relation can give you the distance to a cepheid in another galaxy. Shapley used this relation to determine the boundaries of our galaxy.

8. What are the 3 components of our galaxy, according to Shapley's model? Where is the Sun located in this model? Where is the Galaxy's centre? In what 2 ways is this model incorrect?

Its disk is 300,000 ly in diameter; this large size implied; all nebulae are systems within our galaxy (INCORRECT: actually 100,000 – couldn’t account for dust)Our sun resides in the outskirts of its diskThe Milky Way centre is in Sagittarius

9. Why was Shapley convinced that the spiral nebulae are within our galaxy's boundaries?

spirals are pushed from or disk by radiation pressure from its high density of stars, creating a "Zone of Avoidance". Therefore spirals are within our galaxy

10. What is the Zone of Avoidance? What was Shapley's explanation for it? What was Curtis'? Who was correct?

Shapley: Radiation pressure pushing things out of the galaxy. Curtis: if the milky way's disk contains a band of dust, then if spirals are outside the galaxy, they aren't seen in the "Zone of Avoidance" because they are obscured by the dust. (CORRECT)

11. What observation led Curtis to suspect that the disks of galaxies are filled with interstellar dust? Where does this dust come from?

Heber Curtis completed a high resolution survey of nebulae, revealing obscuring matter ("dust") in their disks.

12. What did Vesto Slipher observe about the spectra of spirals?

he observed that many of them have big redshifts, which suggest that the spirals are receding from us at high speeds

13. In the Shapley-Curtis Debate, what did Shapley argue? What did Curtis argue? What 4 pieces of evidence did Curtis present?

1920: a formal debate was held between Shapley and Curtis: Is our Galaxy the entire universe, or is it one of many Island universes?

14. Who finally resolved the Shapley-Curtis debate? Explain how he did this. What was NASA's tribute to this discovery?

Hubble?

15. Describe (briefly) the 4 types of galaxies in Hubble's Classification system? Which are the most numerous? Which are the least numerous? What are the two types of spiral galaxies? What type of galaxy is the Milky Way?

spirals, ellipticals (least numerous), lenticulars and irregulars (most numerous). spirals can be barred or non-barred. the milky way is a barred spiral

16. What is the Local Group? How does the size of the Milky Way and M31 compare to other galaxies in the Local Group? How did the Milky Way and M31 get this way?

Most galaxies cluster together into gravitationally bound groups of galaxies.

17. What is the Local Supercluster?

The Local Group is part of the "Local Supercluster".

18. What is Hubble's Law? What does the slope of Hubble's Law tell us? What does the inverse of the slope tell us?

Hubble showed: the larger a galaxy's redshift, (or recessional velocity), the further its distance. Slope: rate of Universe’s expansionInverse of the slope: Universe’s Age?

19. Prior to the discovery of Hubble's Law, who had found theoretically that the Universe is expanding?

Einstein.

20. Describe what Einstein referred to as the "biggest blunder" of his career.

He did not believe that the universe could expand or contract, so he created a cosmological constant to fix it. But he was right.

21. Describe the 4 possible fates of the Universe according to Einstein's cosmological equation, including the density and Cosmological Constant associated with each fate. For each fate, state whether Hubble's Constant will increase, remain constant or decrease.

Universe expands at accelerating rate forever: density is less than or equal to, and constant is greater than 0. (Big Chill or Rip)Universe expands forever: density is less than, constant equals 0 (Big Chill)Universe’s expansion halts: density is equal, constant is equal. (Big Freeze) Universe’s expansion halts and contracts: density is greater than and constant is equal to (Bing Crunch)

22. What is the Big Bang theory? What is the Steady State theory? What is the Steady State explanation for Hubble's Law?

Big Bang: the universe began from a single point and is expanding with time, decreasing in density Steady State: the density of a universe is constant as galaxies recede from each other, new galaxies take their place Hubble’s Law: Big Bang theory predicts that galaxies were closer together in the past, while Steady State theory predicts the galaxy spacing has remained constant (?)

23. Describe the 2 pieces of observational evidence for the Big Bang.

1950s: radio surveys of the most distant galaxies revealed that they are closer together than the nearby galaxies The all-sky microwaves were detected (the Cosmic Microwave Background, or CMB)

24. Describe the observational evidence that the expansion of the Universe is accelerating.

A survey of extragalactic supernovae was used and Hubble's Constant (H0) was lower in the past (therefore, the universe is expanding at an accelerating rate, toward a Big Chill or Rip)

25. What does a map of the CMB give us a picture of, and why?

Pictures the distribution of matter 400,000 years after Big Bang. Evidence of Dark Matter (DM).

26. What did WMAP tell us about the composition of the Universe? What effect is "dark energy" believed to be having on the Universe? How is dark energy now accounted for in Einstein's cosmology equation?

Composition With normal matter comprising 27% of the universe (4% we can see, the rest is dark matter) The remaining 73% of the universe may be responsible for the universe's accelerated expansion

27. Describe the ways that dark matter has been detected in galaxies and in intracluster space.

Outer stars not galaxies rotate faster than predicted by a galaxy's visible mass, suggesting the presence of intergalactic DM Gravitational lensing of background galaxies suggest the presence of dark matter in a galaxy halos as well as in the intracluster dark matter (the space between the galaxies in clusters)

Chapter Eleven

1. What are the advantages of radio astronomy compared to visible-light astronomy? Make sure that you understand *why* radio waves have each of these advantages.

can be detected on Earth both night and day (not overwhelmed by sunlight) as well as through clouds easily detected with ground level telescopes (they completely penetrate Earth's atmosphere)

2. Who was the 1st person to detect radio emission from space? Where was this emission coming from? How did he know this?

1931: Jansky ("father of radio astronomy") detected radio emission from our galaxyEmission: strongly emitted by distant (young) galaxies, allowing us to observe galaxies as they appeared in the distant past.

3. When Grote Reber mapped out the radio emission from the Milky Way, what did he find?

"Discrete" radio sources - meaning, spots in the sky that were producing more radio emission than their surroundings. This suggested that there were some sort of radio-producing objects out there.

4. Describe the process that is producing the 21-cm radio emission in our galaxy.

The spin-flip transition of Hydrogen. In a Hydrogen atom, when the magnetic poles of the proton and electron are aligned, the electron eventually flips over. Since the flipped-over state is lover in energy, the electron emits a photon with energy equal to the energy difference between the two states. The energy corresponds to λ = 21cm (Radio)

5. What did maps of the 21-cm radio emission in our galaxy reveal about the structure of our galaxy? Where is the Sun located in this structure?

The maps revealed our Spiral arms. The Sun is located in a spiral arm near the outer disk of our galaxy.

6. What did Stanley Hey identify as the source of the radio emission that was interfering with British radar during WWII?

Solar flares from the sun

7. What are solar flares?

Eruptions of radiation which trace out magnetic field lines from sunspots

8. Describe how the Sun spins. How has this effected the Sun's magnetic field, and What

happens to the Sun's magnetic field every 11 years as a result?

spins differentially ( Its rotation speed decreases with latitude) Magnetic Field: is not a simple bar-magnet, but a complex field which twists and untwists every 11 yrsthis causes the frequency of sun spots ad flares to increase every 11 yrs

9. What causes magnetic storms on Earth?

Caused by winds of charged particles produced by sunspots

10. What causes aurora on Earth? Why are aurora most often seen at high latitudes?

Caused by winds of charged particles produced by sunspots. Seen at high latitudes: that is where the magnetic field is strongest.

11. What happens to the number and intensity of sunspots, magnetic storms and aurora every 11 years, due to the Sun's magnetic cycle?

They increase

12. What was developed in the 1960s to extend the limits of the observable Universe in radio light?

Radio arrays

13. Describe the radio emission from a pulsar. What did Hewish initially suspect that the signal was coming from? What is the true explanation for the pulses? Are all neutron stars pulsars? Why/why not?

1960: pulsating radio signals were detected from the cores of supernova remnants named "pulsars" there are neutron stars (dead cores, energy depleted) whose radio beams are periodically aimed at Earth you see a Pulsar only when the beam isn't aligned with the magnetic poles

14. What is time dilation? How was it proven to exist using pulsars in binary systems?

Binary pulsars were found to tick slower when closest to their center of mass,proving the prediction of General Reactivity that time slows down in a strong gravity field

15. What is a radio galaxy?

Typically giant ellipticals with jets of radio emission from the galaxy's nucleus

16. What does "quasar" stand for? What do quasars look like in visible light? What do they look

like in radio light? What revealed that quasars are distant galaxies?

Quasi Stellar Radio SourcesLook: Star likeRadio: Strong radio sources.The spectra were indicative of galaxies with huge red shifts (i.e billion of ly away)

17. What is currently believed to be the cause of the radio emission produced by radio galaxies and quasars? What is the observational proof in support of this?

Cause: the strong radio lobes are a result if the strong magnetic field produced from the Black hole’s spin The evidence: high-res images of radio galaxies revealed huge disks of hit gas and dust around a central dark object

18. What is the current explanation for why quasars are only seen in the distant Universe?

since only distant quasars are seen, they may be a young phase, when galaxy cores were denser (more fuel for blackhole)

19. What is the current explanation for why radio galaxies aren't as radio-loud as quasars?

all galaxies likely have a central black hole but most are presently quiet having consumed all nearby matter

20. What is suspected to be at the centre of the Milky Way? What is the observational evidence in support of this?

Black hole is in the centre. every galaxy has a blackhole and are tightly packed with stars; highly dense stars imploded into a blackhole

21. What kind of telescope is the Chandra Observatory, and why is it in space?

XRAY telescope. it's in space, cuz our atm blocks xray light.

22. What kind of object is Cygnus X-1? What is believed to be the cause of its X-ray emission? How was this proven in 1972? At what observatory was this discovery made, and in what city?

Cygnus X-1 is the strongest x-ray source discovered. It is proposed to be from an accretion disk around a stellar black hole. In 1972 proof of black holes were found when optical images of Cygnus X-1 revealed a massive star in orbit around an unseen companion. These images were obtained by a U of T professor at the David Dunlap Observatory in Richmond Hill. Ontario.

Chapter Twelve

1. What is the van Karman line? What was the first man-made object to breach it? Who designed this object, and where did he end up working?

Earth’s Boundary. V2 rocket, a german WW2 missile. Wernher von Braun, the german and rocket scientist He later became one of the key architects of the American Space program

2. How were the 1st photographs of Earth taken from space?

the Soviet's 3 Luna craft (unmanned) successfully orbited the Moon, landed on it, and took the first photographs of its far side (not visible from Earth due to the moon's synchronous rotation)

3. What kinds of animals were first launched into space by the U.S (after the fruit flies)? What about the Soviet Union?

Monkeys. Dogs. 4. Which country launched the first satellite into Earth-orbit, and what was this satellite called?

Soviets launched "Sputnik 1", the first unmanned satellite to orbit the Earth. It remained in orbit for three months

5. Which country launched the 1st human into space? Describe how this trip was made.

The Soviet Union launched the first human (Yuri Gagnarin) into space. One orbit around earth, 108 minutes in space, no control of craft (however he was given an override code if needed), upon landing, Yuri deployed from craft once in earth’s atmosphere wearing a parachute.

6. Which country made the first unmanned landings and orbits of the Moon? What did the Luna 3 take photographs of for the 1st time?

Russia. Photographed its far side.

7. Why can't we see the far side of the Moon from Earth? Why is the far side more cratered than the near side?

not visible from Earth due to the moon's synchronous rotation. More cratered: former lava basins.

8. Which country made the first manned landing on the Moon? What was this name of the astronaut who first stepped on the Moon?

America: Neil Armstrong.

9. What is an orbiter? What is a lander? What is a rover?

Orbiter: OrbitsLander: LandsRover: Moves

10. Which planets in our solar system have been landed on by human-made crafts? Were these missions manned or unmanned?

Mars and Venus: unmanned.

11. What did NASA's Space Shuttle consist of? What was its purpose?

Rockets, an orbiter and a space plane. Purpose - to bring humans and cargo to space (primarily to the international space station)

12. What is the International Space Station? What is its purpose?

the ISS, a habitable satellite for conducting space experiments, was launched into Earth orbit in a joint effort by 5 space agencies. It has been continuously occupied for ten years

13. What is the Canadarm? Where are Canadarms permanently installed, and what is their purpose?

the first "canadarm" (15-m robotic arm) was used in a space shuttle mission. Canadarms have now been used in over 50 shuttle missions and are currently installed in ISS

14. What have our space missions left behind around the Earth?

Space Junk

15. What discovery was made when Pete Conrad returned from the Apollo 12 mission to the Moon?

Bacteria on the camera from earth. Proved organisms can survive.

16. What are extremophiles? What are some of the extreme environments on Earth where extremophiles are found?

Extremophiles are life forms that can survive extreme conditions that human can’t. Hydrothermal vents, Antarctic water.

17. What is the Habitable Zone? Which planets in our solar system are in this zone?

Habitable Zone is the region that a planet can be while sustaining liquid water. in our solar system, only Earth is in the zone.

18. What is it about the Carbon atom that makes carbon-based life likely?

Can form complex molecules

19. What 2 surface features of Mars suggest that it could have supported life in the past, and why? What is it about Mars' atmosphere that makes Earth-like life currently unlikely?

Mars polar ice caps contains at least 50% water ice (may have been liquid when the solar system was younger and hotter) Mars canyons are evidence of ancient rivers. These may have held primitive life, which may have enough adapted to the current lack of water and freezing temperatures Atmosphere: No carbon.

20. What was the mission of the Viking space probes? What was concluded on their return, and why?

Viking Space probes were looking for Carbon. They found none, so it was concluded – no life on Mars.

21. What was found when synthesized Martian soil was studied on Earth?

a new detection method found live micro organisms in synthesized Martian soil

22. What is rock ALH 84001? Why does it suggest that life once existed on Mars?

It is a meteorite, but it is a fossil as well.

23. What evidence of water was found by the Phoenix lander? What about the Opportunity rover? What is the mission of the Curiosity rover?

the Phoenix found frozen H2O in Mars' polar ice caps. Opportunity found water-carrying veins in rocks. Curiosity rover will drill into rocks and soil, looking for evidence of sub-surface water

24. Why was the Galileo spacecraft intentionally crashed into Jupiter?

To eliminate any chance of a future impact with Europa that could contaminate the icy moon with terrestrial bacteria.

25. Where is Europa? What is the evidence for liquid water on this celestial body?

Jupiter’s moon. Evidence: found a cracked icy surface on Europa, possibly due to a liquid ocean underneath where temperatures are warmer

26. Where are Titan and Enceladus? What is the evidence for carbon and liquid water on these celestial bodies? What is Titan the only moon in the solar system to possess?

moons around Saturn. they possess ice volcanos, which are spewing h2o and carbon. Titan also has methane lakes (methane contains carbon). Titan is the only moon with a thick atmosphere.

27. What does SETI stand for, and who was its original founder?

The Search for Extra Terrestrial Intelligence. founded by Frank Drake.

28. What is the mission of SETI's Project Pheonix? Has it been successful so far?

Project Pheonix listens for radio transmissions from other solar systems - no success so far

29. What does the Drake Equation measure? Can it currently be accurately solved? Why/why not?

The drake eqn measures the number of communicating civilizations in our galaxy. it can't be solved cuz we don't know the values of all of its terms

30. Briefly describe the 3 attempts that Earth has made to send messages into space. What were the general contents of each message?

The arecibo message, the pioneer plaques, and the voyager record. they all contained information about humans and the planet Earth.

31. Where is Voyager 1 right now?

Voyager-one is approximately 20 years from reaching interstellar space, making it the furthest man made object. It will make its closest approach to a star about two light years away in 40,000 yrs

32. Describe the Doppler-Wobble method for detecting extrasolar planets.

stars with planets wobble back and forth due to the gravity pull of their planets. we can detect that wobble as regular blueshifting and redshifting of the star's absorption lines - blueshift when the star wobbles toward us and redshift when the star wobbles away from us

33. What types of planets are most likely to be found with the Doppler-Wobble method, and why?

Hot jupiters (ie, gas giants that are very close to their stars. why? cuz such planets induce BIG wobbles in their stars, making them easier to detect

34. Why could "Hot Jupiters" not have been born at their present locations? How are they suspected to have reached their present locations?

since a hot Jupiter can't form close to its star (not enough matter), it must have migrated inward. Could earth like planets survive in these systems? Still unknown...

35. What is the goal of the Kepler Mission? How will it aid SETI?

Kepler is looking for Earth-like planets. This will provide SETI with a list of target solar systems to listen to for radio transmissions from intelligent extraterrestrials.

36. Describe the method that the Kepler Mission is using to detect extrasolar planets.

The transit method. Kepler looks for a periodic drop in light from a star, which is indicative of a planet passing in front of the star.

37. Is Kepler surveying a large or small fraction of the stars in the Milky Way? Based on their preliminary results, our Earth-like planets common or rare? Has Kepler found any planet candidates in the Habitable Zone? How about Earth-like planet candidates in the Habitable Zone? How many planets in the Habitable Zone have been projected for our entire Galaxy?

Tiny fraction of stars in the Milky Way. Yes, earth-like planets are common. Yes, some found in the Habitable Zone, including earth-like. Millions of planets in Habitable Zone projected for our entire galaxy.

38. Describe how planets can be investigated for Earth-like habitability and signs of life.

You take a spectrum of a star when its planet is passing in front of it, then you take another spectrum when the planet is NOT in front of the star. By subtracting the two spectra, U get the spectrum of the planet's atmosphere. If this spectrum looks the like the spectrum of our atmosphere, that tells us that the planet has an earth-like atmosphere, if the spectrum contains artificial pollutants, then we can guess the planet has life on it.

ARTICLE yep - the article is on the galaxy seen through a gravitational lens