Chapter 4 Flashcards
Which component of the galaxy contains small, old, red stars with no new star formation
The Galactic Bulge/ Center
Which component of the galaxy contains much star formation, younger/bluer stars, and lots of gas/dust
The Disk
What fill the space between stars?
The Interstellar medium
Is the interstellar medium uniform throughout the galaxy?
No, it varies in temperature, make-up, and number density
What is the name of the clouds which contain gas and dust in the ISM?
Nebulae
To what SS object does the ISM have similar composition?
The Sun
What are the 5 components of the ISM (in descending temperature)?
Cornal Gas, Intercloud Gas, Inonized Hydrogen, Netural Hydrogen, Giant Molecular Cloud (GMC)
What is the radii and mass of the average GMC?
Approx 10^5-10^6 solar masses, and 60-200 lys
Which GMC is closest to the Sun?
The Orion Nebula
As a GMC begins to collapse under its own gravity, it heat up. Why?
Because of the friction between particles that are colliding in their plummet to the center
As what point is a star born in a nebulae?
Once the nebulae is hot enough to support fusion
What stops the collapse of the newborn star?
The pressure that has built up as the nebulae heats and compresses
How is a protostellar disk formed?
Angular momentum of the cloud if conserved (angular velocity increases and radius decreases)
What are the 3 layers of the surface of the Sun?
Photosphere (dense, opaque gas), Chromosphere (thin, transparent gas), Corona (thin transparent gas)
Which is hotter: the photosphere or corona?
The corona (6000K vs 1 million K)
What is the main energy transport in the photosphere?
Convection
What is the “visible consequence of convection”?
Granulation causes the Sun to appear spotty
Define blackbody
An idealized system that absorbs and re-radiates all incident radiation of all wavelengths
In what emission are chromospheric structures visible?
In the H-alpha emission
Define solar wind
A constant flow of particles “boiling” off the Sun
What is the Sun’s Mass loss per year?
10^7 tones per year
What are sun spots?
Cooler regions on the Suns photosphere
To what physical property are sun spots related?
They are related to magnetic activity
Though dark in visible light, in what EM range are sun spots bright?
In the UV range
Why do sun spots usually come in pairs?
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
Why is solar material able to interact with a magnetic field?
Because the gas has become a plasma and therefore its electrons are far enough away from the protons that the material is not neutral
Why is the plasma in a sun spot darker?
Because sun spots have strong magnetic fields which trap and hold plasma, preventing convection. Plasma cools below average T of the Sun
What are solar flares/ mass coronal ejections?
When the sun flings plasma into space, due to the breaking of the magnetic field between 2 sunspots
What is the solar cycle?
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)
What is the Mauder Minimum
A period of quiet solar activity which coincided a “little age age”
What is the solar constant?
The total energy (all wavelengths) from the Sun that falls on Earth per square meter
What process produces energy in the Sun?
Nuclear fusion (fusing together 2 or more atomic nuclei to produce heavier elements)
Why is high proton speed needed to begin fusion?
The protons must have enough energy (kinetic) to overcome the Coulomb Barrier (EM repulsion between protons)
What is the process the Sun uses to convert H into He?
The proton-proton chain
Why can we no see directly into the Sun’s core?
Because the photosphere is opaque
What method do we use to “see” into the Sun’s core?
Neutrino detection
What as the solution to the solar neutrino problem?
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
What force balance in a hydrostatic equilibrium?
Pressure force pushing outward and a gravitational force pushing inward
How does a main sequence star become a red giant?
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
What is the minimum mass for a star to be able to fuse carbon and oxygen?
2 solar masses
What happens to a 1 solar mass star after its helium fusion ceases?
The outer layers drift away to become a planetary nebula, the core becomes a white dwarf (and eventually black dwarf)
Which burns faster: larger or smaller stars?
Larger stars (t= Mc^2/L)
Which its the last element that can be fused by high mass stars?
Iron, because it is the most tightly bound nucleus
What initial size must a star be to produce a supernova and a neutron star?
8Msun<13Msun
What initial size must a star be to produce a supernova and a black hole?
Mstar> 13Msun
Why are supernova important in the formation of our SS?
Because all of the heavy elements in the universe were created in the cores of massive stars and ejected via supernovas
