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Astronomy 2201B > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

Which component of the galaxy contains small, old, red stars with no new star formation

A

The Galactic Bulge/ Center

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2
Q

Which component of the galaxy contains much star formation, younger/bluer stars, and lots of gas/dust

A

The Disk

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3
Q

What fill the space between stars?

A

The Interstellar medium

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4
Q

Is the interstellar medium uniform throughout the galaxy?

A

No, it varies in temperature, make-up, and number density

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5
Q

What is the name of the clouds which contain gas and dust in the ISM?

A

Nebulae

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6
Q

To what SS object does the ISM have similar composition?

A

The Sun

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7
Q

What are the 5 components of the ISM (in descending temperature)?

A

Cornal Gas, Intercloud Gas, Inonized Hydrogen, Netural Hydrogen, Giant Molecular Cloud (GMC)

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8
Q

What is the radii and mass of the average GMC?

A

Approx 10^5-10^6 solar masses, and 60-200 lys

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9
Q

Which GMC is closest to the Sun?

A

The Orion Nebula

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10
Q

As a GMC begins to collapse under its own gravity, it heat up. Why?

A

Because of the friction between particles that are colliding in their plummet to the center

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11
Q

As what point is a star born in a nebulae?

A

Once the nebulae is hot enough to support fusion

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12
Q

What stops the collapse of the newborn star?

A

The pressure that has built up as the nebulae heats and compresses

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13
Q

How is a protostellar disk formed?

A

Angular momentum of the cloud if conserved (angular velocity increases and radius decreases)

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14
Q

What are the 3 layers of the surface of the Sun?

A

Photosphere (dense, opaque gas), Chromosphere (thin, transparent gas), Corona (thin transparent gas)

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15
Q

Which is hotter: the photosphere or corona?

A

The corona (6000K vs 1 million K)

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16
Q

What is the main energy transport in the photosphere?

A

Convection

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17
Q

What is the “visible consequence of convection”?

A

Granulation causes the Sun to appear spotty

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18
Q

Define blackbody

A

An idealized system that absorbs and re-radiates all incident radiation of all wavelengths

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19
Q

In what emission are chromospheric structures visible?

A

In the H-alpha emission

20
Q

Define solar wind

A

A constant flow of particles “boiling” off the Sun

21
Q

What is the Sun’s Mass loss per year?

A

10^7 tones per year

22
Q

What are sun spots?

A

Cooler regions on the Suns photosphere

23
Q

To what physical property are sun spots related?

A

They are related to magnetic activity

24
Q

Though dark in visible light, in what EM range are sun spots bright?

A

In the UV range

25
Q

Why do sun spots usually come in pairs?

A

They are typically acting like a bar magnet, with one spot the north pole and one the south, and a magnetic field arching between them

26
Q

Why is solar material able to interact with a magnetic field?

A

Because the gas has become a plasma and therefore its electrons are far enough away from the protons that the material is not neutral

27
Q

Why is the plasma in a sun spot darker?

A

Because sun spots have strong magnetic fields which trap and hold plasma, preventing convection. Plasma cools below average T of the Sun

28
Q

What are solar flares/ mass coronal ejections?

A

When the sun flings plasma into space, due to the breaking of the magnetic field between 2 sunspots

29
Q

What is the solar cycle?

A

An 11 year cycle in which the number of sun spots fluctuates (two cycles,22 years, is a total reversal of the suns magnetic field)

30
Q

What is the Mauder Minimum

A

A period of quiet solar activity which coincided a “little age age”

31
Q

What is the solar constant?

A

The total energy (all wavelengths) from the Sun that falls on Earth per square meter

32
Q

What process produces energy in the Sun?

A

Nuclear fusion (fusing together 2 or more atomic nuclei to produce heavier elements)

33
Q

Why is high proton speed needed to begin fusion?

A

The protons must have enough energy (kinetic) to overcome the Coulomb Barrier (EM repulsion between protons)

34
Q

What is the process the Sun uses to convert H into He?

A

The proton-proton chain

35
Q

Why can we no see directly into the Sun’s core?

A

Because the photosphere is opaque

36
Q

What method do we use to “see” into the Sun’s core?

A

Neutrino detection

37
Q

What as the solution to the solar neutrino problem?

A

Neutrinos change between 3 different types: electron, muon, and tau neutrinos. The detectors were only picking up the electron neutrinos and therefore only saw 1/3 of the expected amount

38
Q

What force balance in a hydrostatic equilibrium?

A

Pressure force pushing outward and a gravitational force pushing inward

39
Q

How does a main sequence star become a red giant?

A

After all hydrogen has fused, core is left as helium “ash”. The lack of fusion means no outward pressure, so the star contracts. Helium flash occurs, and the outer layers expand and cool

40
Q

What is the minimum mass for a star to be able to fuse carbon and oxygen?

A

2 solar masses

41
Q

What happens to a 1 solar mass star after its helium fusion ceases?

A

The outer layers drift away to become a planetary nebula, the core becomes a white dwarf (and eventually black dwarf)

42
Q

Which burns faster: larger or smaller stars?

A

Larger stars (t= Mc^2/L)

43
Q

Which its the last element that can be fused by high mass stars?

A

Iron, because it is the most tightly bound nucleus

44
Q

What initial size must a star be to produce a supernova and a neutron star?

A

8Msun<13Msun

45
Q

What initial size must a star be to produce a supernova and a black hole?

A

Mstar> 13Msun

46
Q

Why are supernova important in the formation of our SS?

A

Because all of the heavy elements in the universe were created in the cores of massive stars and ejected via supernovas

Astronomy 2201B (11 decks)

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