Astronomy midterm questions

• the sun isn't getting bigger or smaller
• gravity and pressure are in equilibrium
• the balance between the thermal pressure (outwards) and the weight of the material above pressing downward (inwards).

• the sun is not changing in temperature due to expansion and contraction, depending on the necessary condition. 
• if the sun cools down, it will contract and heat up from the inside.
• if the sun heats up, it will expand and cool down

1 million joules

28 minutes

• coming together
• small nuclei stick together to make a bigger one
• high temperatures enable fusion to happen in the core
• it occurs in sun and stars

• 1 million K
• outermost layer of the solar atmosphere
• appears bright in X-ray photos in places where magnetic fields trap hot gas

• 3rd layer of the sun (from inside out) where energy is transported upward by rising hot gas
• convection is the primary mechanism for the outer 29% of the sun's radius

• about 6000 K
• 4th layer of the sun (from inside out) 
• the visible surface of the sun. the layer that we see

• 15 million K
• 1st layer of the sun (from inside out) and energy is generated by nuclear fusion in the core

• 2nd layer of the sun (from inside out) and energy is transported upward by photons
• radiation (diffusion of photons) is the primary mechanism for the first 71% of the sun's radius
• energy leaks out of the radiation zone in forms of randomly bouncing photons

• about 10 000 - 100 000 K
• 5th layer of the sun (from inside out) and is the middle layer of the solar atmosphere

• 7th "layer" of the sun
• a flow of charged particles from the surface of the sun

• 3.0 x 10⁸ m/s
• is a measurement of time, not distance
• "c"

• breaking apart
• big nucleus splits into smaller pieces
• occurs in nuclear power plants

• how hydrogen fuses helium in the sun 
• 4 protons ⇒ ⁴He, 2 gamma rays, 2 positrons, 2 neutrinos, energy
• the sun releases energy by fusing 4 hydrogen nuclei into 1 helium nucleus and energy, in a 3 step process

• keeps burning rate steady
• decline in core temperature causes fusion rate to drop, so core contracts and heats up
• rise in core temperature causes fusion rate to rise, so core expands and cools down 
• this is what keeps the sun in equilibrium

• the weakest force in nature, but controls the strongest force in nature
• 9.81 m/s²

• rising hot gas
• takes energy to the surface 
• ex. soup bubbling b/c it was left on the stove for too long

• Temperature: average kinetic energy of the particles (molecules) in a substance. dominated by the velocities of the particles
• Heat: the total kinetic energy of a substance. thermal energy

a³/p² = 1 (only for the sun)

• 1) each planet's orbit around the sun is an ellipse, with the sun at one focus 
• 2) as a planet moves around its orbit, it sweeps out equal areas in equal times
• 3) the square of a planet's orbital period is proportional to the cube of its average distance from the sun (semi-major axis). p²=a³

Kepler's laws allow us to determine mass

• proton, neutron ⇒ nucleus ⇒ electrons.
• electrons are smeared out
• the nucleus is the smallest part of the atom, but it contains most of the atom's mass
• atomic number: number of protons
• atomic mass: sum of the protons and neutrons

• forms of an element that have the same number of protons but different number of neutrons 
• mass will be different
• ex. deuterium

• solid: atoms and molecules are held tightly in place
• liquid: atoms and molecules remain together, but move freely
• gas: atoms and molecules move essentially unconstrained
• plasma: free electrons move among positively charged ions

as temperature increases, the bonds are loosened

• Kinetic energy: energy of motion. 1/2 mv²
• Potential energy: stored energy/mass energy. E=mc². speed of light is 3.0 x 10⁸
• Radiative Energy: energy transported by light 
• Gravitational Potential energy: (object/gas cloud has more GEP when it's spread out. a contracting cloud converts GEP to thermal energy)

speed of light is 3.0 x 10⁸ m/s. emission line (give off, bright spectral lines), absorption line (take in, dark spectral lines, there's a cutoff limit), continuous (incandescent light bulb, visible wavelengths) transmission (passing on, transparent objects), reflection (sending back, mirrors), scattering (deflecting/diffusion, movie screens). photons are particles of light. light travels in electromagnetic waves and doesn't need matter or material to carry its energy along. c= frequency X wavelength.

speed of sound is 340 m/s. needs matter or material to carry its energy along.

• AM stations are kilohertz (KHz)
• FM stations are megahertz (MHz)

• the effect that shifts the wavelengths of spectral features in objects that are moving toward/away from the observer
• Doppler shifts tell us only about the part of an object's motion toward or away from us. Curved surfaces don't give an echo.

follows the average motion of material in the Milky Way, in the neighbourhood of the Sun

generally the heaviest ion

an object emits energy at a rate which depends on the fourth power of its temperature. it's measured in W/square meter and is called the energy flux.

F = σT⁴

• σ= 5.67 x 10^-8 Wm^-2 K^-4
• L= surface area x F= σT⁴ x 4piR² = 4σpiR²T²

• a small change in temperature = a big change in luminosity
• overweight stars are bad.

• the wavelength of maximum emission is given (where wavelength is measured in meters and T is measured in Kelvin) by wavelength_maxT = 0.0029 mK
• the relationship b/w the energy of an object and its wavelength emission. the product is a constant.

• 13.73 billion years, to be exact
• about 14 billion years old

• a perfect absorber that reflects no energy
• blackbodies keep people cooler b/c they trap air. air is the best insulator.
• blackbodies create an air gap

• the smallest separation in angle b/w two objects. 
• the minimum angular separation that the telescope can distinguish
• ultimate limit to resolution comes from interference of light waves within a telescope
• larger telescopes are capable of greater resolution b/c there is less interference
• advantages to bigger telescopes: more light comes in, higher resolution, D⁴

• the study of the magnetic properties of electrically conducting fluids
• ex. plasma, liquid metal, salt water, electrolytes

• "lady computers"
• butterfly diagram
• The Heavens and Their Story
• original name was Annie Russel

through convection (rising hot gas)

watts per square meter

• the apparent shift in position of a nearby object against a background of more distant objects
• apparent positions of nearest stars shift by about an arcsecond as earth orbits the sun
• parallax angle depends on distance
• parallax is measured by comparing snapshots taken at different times and measuring the shift in angle to star

• the distance at which 1 AU subtends an angle of 1 arcsecond 
• 1 pc = 206 260 AU = ~3.26 light years

• 1°= 60 arcminutes
• 1 arcminute = 60 arcseconds
• ∴ for every degree, there are 3600 arcseconds.

• developed by the Greeks 
• m = apparent brightness, M = absolute magnitude.
• brightness star 1 ÷ brightness star 2 = (100^1/5)^M1-M2
• Luminosity star 1 ÷ Luminosity star 2 = (100^1/5)^M1-M2
• Absolute magnitude is the magnitude a star would have if it was placed at 10pc

10⁶ - 10^-4

• Luminosity (L= j/s or watts)
• Mass (most important property, drives everything) 
• Composition (what the star is made of)
• Temperature (average kinetic energy)

• non-eclipsing, 1 set of lines moving back and forth.
• orbits a black hole
• through spectrum binary, you can tell the mass of a black hole

b/c they are full of free electrons

• 1 million years
• b/c you don't see hydrogen. it's been ionized

• Wein's Law and Spectral Type (the group in which a star is classified according to its spectrum)
• Spectral Type is more precise

• stars viewed through the edges of the cloud look redder b/c dust blocks blue light/shorter wavelengths more effectively than red light/longer wavelengths.
• long- wavelength infrared light passes through a cloud more easily than visible light
• observations of infrared light reveal stars on the other side of the cloud

women measured the spectral templates of stars, therefore figuring out the temperatures

• particles (electrons) can't be in the same place, laws of quantum mechanics prohibit it
• Degeneracy pressure doesn't depend on heat content
• it stops the contraction of objects < 0.08Msun before fusion starts

• hotter temperature to the left, higher luminosity when further up
• depicts temperature, colour, spectral type, luminosity and radius

the instability strip is a region in the HR gap, occupied by pulsating stars in a post main-sequence stage of stellar evolution

• High-mass stars > 8 Msun
• Intermediate-mass stars are b/w 2 Msun and 8 Msun
• Low-mass stars <2Msun
• Brown dwarfs

an empirical function that describes the distribution of initial masses for a population of stars

a line on a diagram/map connecting points relating to the same time or equal time.

• heterogeneous set of stars with unusual spectra showing prominent broad emission lines of highly ionized helium and nitrogen or carbon
• drudge up stuff

• high-mass main sequence stars fuse H to He at a higher rate using carbon, nitrogen and oxygen and catalysts
• greater core temperature enables H nuclei to overcome greater repulsion
• one of 2 sets of fusion reactions, the other being the proton-proton chain

a set of nuclear reactions by which 3 helium-4 nuclei (alpha particles) are transformed into carbon

• it's under-abundant 
• the universe can't make it efficiently

the stage in stellar evolution that immediately follows the red giant branch in stars whose masses are similar to the sun