Final Exam

Front 1

Galaxy had to be ******* in shape

Back 1

spiral (only 5 percent are spiral)

Front 2

No-nos for location

Back 2

can't be in a rich cluster - mergers and collisions would be too frequent

Front 3

Needs for location

Back 3

nearby dwarf galaxies to supply dust and gas for the Milky Way's spiral structure

Front 4

Elliptical Galaxies are no-nos because....

Back 4

no dust or gas or heavy elements to make a life-supporting planet

Front 5

Irregular Galaxies are no-nos because....

Back 5

too big - radiation destroys life

too small - same story as Elliptical Galaxies

Front 6

define co-rotation point

Back 6

At the co-rotation point the Sun remains stationary and out of a spiral arm.

Front 7

Must be near but not inside *****

Back 7

a spiral arm

Front 8

Why it is bad to be inside the spiral arm (where most Milky Way stars are located)

Back 8

the star densities are too high – the planetary orbits would be unstable

Front 9

Only one star! Why?

Back 9

1) Gravity from two or more stars would make stable planetary orbits impossible.
2) If no star - there would be no energy source

Front 10

Must be a **** type star

Back 10

G-type star

Front 11

Why only a G-type star?

Back 11

1) If hotter, UV would extinguish life
2) If cooler, would have to be so close that tidal effects of the star on the planet would slow the planet’s rotation

Front 12

The right....

Back 12

Hary Habitable zone
Gave (surface) Gravity
Rose Rotational period
Much Magnetic field
Heat source
Peed (water or some other liquid)

Front 13

MUST BE IN THE HABITABLE ZONE Why?

Back 13

(Water at the triple point), distance within 2%

Front 14

MUST HAVE THE RIGHT SURFACE GRAVITY Why?

Back 14

1) If too high, hydrogen and helium would be retained
2) If too low, the atmosphere would dissipate into space (within 2%)

Front 15

MUST HAVE THE RIGHT ROTATIONAL PERIOD Why?

Back 15

1) If too fast, circulational weather pattern would be too severe
2) If too slow, the day/night temperature variation would be too great

Front 16

MUST HAVE A MAGNETIC FIELD Why?

Back 16

Needed for protection from the Solar wind

Front 17

MUST HAVE A CENTRAL HEAT SOURCE (AN UNUSUALLY LARGE CORE) TO DRIVE TECTONIC ACTIVITY Why?

Back 17

The Earth’s surface would erode to the extent that life would not survive unless the Earth’s crust was constantly replenished.

Front 18

MUST HAVE WATER (OR SOME OTHER LIQUID) Why?

Back 18

To lubricate the tectonic activity

Front 19

NEED A GIANT OUTER PLANET LIKE JUPITER Why?

Back 19

It takes the hit from asteroids and comets eliminating catastrophes on Earth

Front 20

NEED A LARGE MOON IN ORDER TO Why?

Back 20

1) Stabilize the Earth’s axial tilt
2) Create tides which wash the Earth’s surface cleansing the oceans and mixing oxygen from the air into the water to support marine life.

Front 21

HUGH ROSS

Back 21

LISTS 322 unique characteristics of the Earth

Front 22

Hugh says probability of finding life on another Earth (when calculated with one planet for Star) is ...

Back 22

10 to the negative 304

Front 23

Mercury/Venus are too **** to support life

Back 23

hot

Front 24

Earth was ****** for life

Back 24

just right

Front 25

Mars was ***** once but now too ***** for life

Back 25

OK

cold

Front 26

Jupiter, Saturn, Uranus, Neptune are too ***** to support life

Back 26

cold

Front 27

Optimal Temperature range for life is...

Back 27

T<100 degrees C
T> 0 degrees C

since water is a great solvent

Front 28

What sets planet temperatures?

Back 28

Solar Radiation (Solar flux)
Albedo
Rotational Rate
Distance
Heat sinks on Earth
Chemical changes
Photosynthesis

D CHARPS

Front 29

Assume that the dominant factor is stellar radiation (energy equation)

Back 29

Total Energy (Absorbed) = Total Energy (radiated)

Front 30

The zone in a stellar system where water is in liquid form (at least some of the time)

Back 30

the habitable zone

Front 31

Hertzsprung-Russell Diagram

Back 31

y axis = luminosity
x axis = temperature

Front 32

Most stars are **** stars

Back 32

M

Front 33

excluding M stars, about ***** of all the rest of stars are K stars

Back 33

1/2

Front 34

the range of distance from an M star that contains habitable life is very *****

Back 34

small

Front 35

M Star Problems

Back 35

1)Habitable zone is VERY close to the star
2) Gravitational/tidal forces are much stronger here, so we expect tidal locking may develop this close (everything goes outwards towards the star)

Front 36

More M Star Problems

Back 36

M stars have very active magnetospheric storms and flares

Front 37

Habitable Zones: O/B stars pros and cons

Back 37

pros - Range in distance from the star is huge. We expect many planets in this range
cons - short life times

Front 38

How long does an O star live?

Back 38

428,000 years (biggest type of star)

Front 39

How long does an A star live?

Back 39

longer than an O star or B star

Front 40

How long does a B star live?

Back 40

longer than an O star but less than an A star

Front 41

What stars are the likeliest targets in searching for extraterrestrial life?

Back 41

Late F stars (F5)
G stars (yeah us!)
K stars

Front 42

Where around these late F, G, and K stars do we look for life?

Back 42

the habitable zone

Front 43

Life on Venus?

Back 43

1) Venus is MUCH hotter (by about 60K) than we expected
Due to its thick atmosphere and greenhouse gases

Front 44

So … thick atmosphere can “ruin” a planet in the close end of the HZ or it can...

Back 44

keep a planet just outside the distant end of the HZ “warm”

Front 45

What about life on Europa/Enceladus ?

Back 45

These moons seem to have liquid water (potentially in VERY large quantities)

Front 46

What is Europa?

Back 46

moon of Jupiter

Front 47

What is Enceladus?

Back 47

moon of Saturn

Front 48

How did Europa get water on it?

Back 48

At great distance from the nice warm sun and no atmosphere to trap surface heat, the very top is clearly solid ice. But thanks to internal heat from tidal forces, Europa appears to have a liquid layer

Front 49

How did Enceladus get water on it?

Back 49

But scientists have been surprisingly divided about whether the insides of Enceladus are liquid or solid ice, with a process called sublimation (solid turning directly to gas) generating the water vapor-filled plumes.

Front 50

Most stars are in ******

Back 50

binary systems

Front 51

Could life live on a binary system?

Back 51

1) maybe - going in an out of habitable zone would be tough on life
2) even if planet stabilized between 2, then it would probably be too far away to still be in the habitable zone

Front 52

Stars in the inner galaxy are....

Back 52

densely packed - lots of issues with supernovaes and such

Front 53

stars in the outer galaxy are less *******

Back 53

"chemically evolved" - not that much C or O

Front 54

If we assume temperature is dominated by sun/star-light, then....

Back 54

the HZ can be calculated for any given star

Front 55

Likely star types for life are....

Back 55

F, G, and K stars

Front 56

A vortex coronagraph

Back 56

based on the fact that, due the extreme distances of the stars, we can treat their light as being coherent. Using diffraction to blank out the central images we can see. You then rotate the diffractor around a 360 degree circle to reveal the planets near it.

Front 57

Alex Wolczan

Back 57

In 1992 he discovered 2 (now 3) planets around a neutron star (seemed weird tho, maybe remnants from supernova)

Front 58

Kepler described

Back 58

3 “laws” of planetary motion (for our solar system)

Front 59

Newton later used his physical laws of motion to show...

Back 59

WHY Kepler’s rules for planet motion worked

Front 60

Kepler’s First Law

Back 60

1) Planet orbits are ELLIPSES
2) The sun/star is at one “focus” of the ellipse
3) Both the planet and the star orbit the center of mass
4) The distance from the center to the focus is c=ae where e is the “eccentricity”

Front 61

What is an ellipsis?

Back 61

Circles are ellipses with eccentricity=0 (both foci at center)

Front 62

Kepler's Second Law

Back 62

Planet motion sweeps out equal areas of the ellipse in equal time
Meaning … planet moves faster when it is closer to the star and slower when it is farther away

Front 63

Kepler’s Third Law

Back 63

a3/P2 = Mtot
a = semi-major axis of the ellipse (AU)
P = period of the orbit (years)
Mtot = total mass of the system (solar masses)

Front 64

What does a represent in Kepler's Third Law?

Back 64

a = semi-major axis of the ellipse (AU)

Front 65

What does P represent in Kepler's Third Law?

Back 65

period of the orbit (years)

Front 66

What does Mtot mean in Kepler's Third Law?

Back 66

Mtot = total mass of the system (solar masses)

Front 67

For a star/planet system, the ***** does most of the moving

Back 67

planet

Front 68

The BaryCenter is the **** of the solar system

Back 68

center of mass

Front 69

Radial Velocity Planet Searches

Back 69

1) So … need a speedometer to measure star velocity versus time
To a precision of a few meters per second!
Across distances of many light years!!!
How? Doppler shift of spectral lines

Front 70

***** has biggest reflex velocity effect on the Sun

Back 70

Jupiter

Front 71

51 Pegasi

Back 71

In 1995, Mayor & Queloz announce the discovery of an orbital signature with amplitude = 50 m/s in a 4.23-day period around star 51 Pegasi
Mass = 0.5 MJUP  First extra-solar planet

Front 72

At 51 Pegasi's location...

Back 72

extremely hot! Size of Jupiter but closer to the sun than Mercury O_O

Front 73

Geoff Marcy & Paul Butler

Back 73

confirmed Pegasi 51

Front 74

most extra-solar planets known today are

Back 74

"Hot Jupiters"

Front 75

“MARVELS” (Multi-object Apache Point Observatory Radial Velocity Exoplanet Large-area Survey)

Back 75

is the UF’s program launched in 2008 that promises to be one of the most prolific of all exoplanet hunting programs.

Front 76

How many known extra-solar planets are there?

Back 76

763

Front 77

All of this has happened in about 20 years –

Back 77

someone currently finds a new planet every couple of weeks or less