Close Quiz 4? (weeks 11 &12)

Question 1

How are stars classified?

Answer 1

Classified by their temperatures and luminosities into 7 spectral types O B A F G K M

Question 2

Describe spectral type O stars.

Answer 2

Are the hottest of the stars
Blue in color
Burn out faster

HOT, HIGH MASS, SHORT LIVES & EXPLODE

Question 3

Describe spectral type M stars.

Answer 3

Coolest of the stars
Red in color
Doesn’t burn fast

COOL, LOW MASS, LIVE LONG LIVES (600- billion to a trillion

Question 4

What type of star is the Sun?

Answer 4

G star

Question 5

Why is it that more massive stars are hotter & live shorter lives, while low mass stars are cooler & have very long lifetimes.

Answer 5

The more massive the star the greater the inward force of gravity (the increases pressure from the stars nuclear reacts by pushing outward]

Nuclear fusión is unbalanced
Too much energy

Question 6

Which types of stars are most likely to have life around them?

Answer 6

K stars (maybe)

Question 7

What is a brown dwarf?

Answer 7

“Failed” stars - not massive enough to sustain fusion but too massive to be called a plant (not bound to a star;free floating)

Starts warm but cools over time (as they age they get hard to find)

Size: 13-17 times jupiters mass

Question 8

How does the position of a habitable zones change with the type of the star?

Answer 8

HZs are far from hot stars (much further out) & closer around cool stars

Question 9

What are some of the problems for planets orbiting close to M type stars?

Answer 9

• They have tiny HZs
• To orbit M stars, earth like planets would have to be very close to a star to get enough heat
• young M stars have intense solar flares that can strip away planetary atmospheres and bombard surfaces

Not the best place to find planets with life

Question 10

What spectral type star may be the best suited to have planets with life? Why?

Answer 10

K star (maybe) - more common and longer lived than G but without the flaring of M stars (sweet spot)

Question 11

What are the two kinds of situations where planetary orbits can be stable in binary star systems? What is a circumbinary planet?

Answer 11

1. Stars orbit close together & planet(s) orbit far away (circumbinary planet)
   
   • planet(s) orbit the stars common center of mass
   • if planet is too close to the stars it’s orbit unstable and ejects from system
   • feels like it’s circling 1 star
2. Stars orbit far apart & planet (s)

Question 12

What are the habitable zones like in the two main types of binary systems where planets can be found?

Answer 12

CLOSE BINARY: HZs position is based on the total energy of both stars

WIDE BINARY: an HZ around each star

Question 13

Describe the direct photography method for finding exoplanets.

Answer 13

Very difficult: photographing a small faint thing next to one brighter that is far away

ONLY 1% OF EXOPLANETS FOUND THIS WAY

to have great chance of success, astronauts use tool known as CORONAGRAPH

Question 14

What is a coronagraph?

Answer 14

A disk used to block the light of a star so as to be able to see faint objects nearby

Question 15

Describe the Doppler (aka radial velocity) method for finding exoplanets.

Answer 15

As a planet & star orbit their baycenter (center of mass between 2 bodies), the star moves alternately towards (blueshift) and away (redshift) from us revolving the planet orbital period

ABOUT 19% EXOPLANETS FOUND THIS WAY

Best suited for finding big planets that are close to their stars

Least likely to discover earth like planets around sunlike stars

Question 16

What is a barycenter?

Answer 16

Center of mass between the two bodies

Question 17

Describe the transit method for finding exoplanets.

Answer 17

Too far to see as disks so instead the brightness of a star is measured

Planet passes in front of its start dimming its light (eclipse)

MOST SUCCESSFUL ABOUT 77% OF EXOPLANETS FOUND THIS WAY

Question 18

What are the limitations for this method?

Answer 18

If the orbit is tipped no ras it can be seen

Face on (angle from above): no planet orbit

Question 19

What is actually “seen” during a planetary transit?
What properties of a planet can be measured from a transit?

Answer 19

A planet passes in front of its star dimming (eclipse)

Transit can tell us the orbitals period, orbital distance, and size of exoplanet

In some cases mass —> mass+size=density

Question 20

How can a transit be used to investigate a planetary atmosphere?

Answer 20

A transiting exoplanet with an atmosphere will show something similar as it filters the light of its star

CHECK EXOPLANET ATMOSPHERE NOTES

Question 21

What is microlensing? How can a planet be found through microlensing?

Answer 21

Takes advantage of general relativity (massive objects bending) to magnify images of distant stars

ABOUT 2.5% OF EXOPLANETS FOUND THIS WAY

-detect planets of great distances
-best suited 4 planets that are moderately far from their star
-best way of finding rouges free floating planets

Question 22

What method for finding exoplanets is best suited for finding Earth-like planets?

Answer 22

Transit method

Question 23

What is the most common type of planet that has been found?

Answer 23

Bigger than earth but smaller than Neptune

About 5% not found in our solar system

Question 24

What is a hot Jupiter?

Answer 24

Hot Jupiters are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods. The close proximity to their stars and high surface-atmosphere temperatures resulted in their informal name “hot Jupiters

Question 25

What is a super Earth?

Answer 25

Rocky worlds with up to 10x earths mass

Not all are earth like

CHECK TYPES OF EXOPLANETS NOTES

Question 26

What is a mini-Neptune?

Answer 26

Gaseous worlds with up to 10x earths mass

Our solar system might have an undiscovered mini Neptune

Theorized 9th planet in out SS may orbit behind inner planets

CHECK TYPES OF EXOPLANETS NOTE