cacca
18. What is an eclipsing binary? How do astronomers determine the orbital period of an eclipsing binary?
An eclipsing binary orientated so that the stars pass in front and behind each other as seen from earth. Most eclipsing binaries are not resolved.
What is a typical LIFETIME for an O-type main sequence star? M-type?
50 billion
Approximately how long will it take for the (light) energy created in the core of the Sun right now to get to Earth? How long will it take the tiny neutral particles created right now to get to Earth?
70,000 to a million is how long it will take. 8 min
7. If you plot luminosity against temperature for the stars in the universe, what do you find?
90 percent of the stars lie in a narrow band where temp is directly related to luminosity.
What is a typical mass (in solar masses) for an O-type main sequence star? M-type?
360 thousand is the typical mass of an O-type
Describe in detail why an O-type main sequence star does not live longer than an M-type main sequence star. What are their "fuel tank" sizes? What is the luminosity of each? How are luminosity, fuel tank size, and lifetime related? Give an analogy with cars.
A star's mass gives a measure of the amount of "fuel" and its luminosity gives a measure of the rate at which this fuel is consumed. So a star's lifetime is proportional to its mass divided by luminosity. Since O type is hotter than M type it burns its gasses quicker. Making O type the most luminous but have a smaller fuel tank size and lifetime.
What happens to THE CORE of a star IMMEDIATELY after the core hydrogen fuel runs out?
The core can;t hold itself up anymore and the gravity begins to push in.
What is a planetary nebula? What sort of spectrum do astronomers see from the outer layers of a planetary nebula? What is at the heart of a PN?
The planetary nebula is when the outer layer leaves the core. They see emission. The white hot core
What is a white dwarf? Describe a typical white dwarf (composition, temperature, radius, mass, location on the HR diagram).
The white dwarf remains of a star that ran out of fuel for nuclear fusion. Small dense star that is the size of the planet, bottom left side , star with the smallest radius and mass and hottest temp
What phases of a star's formation and life are common to both HIGH MASS and LOW MASS stars?
They both start off with fusing hydrogen into helium.
Where would you find a high temperature MAIN SEQUENCE star
Top left yes is
6. Betelgeuse has a luminosity that is much larger than HD 25329's. How is that possible?
It can have a bigger luminosity because it can be bigger in size compared to HD
19. If an O-type star is in a binary orbit with a similar-sized G-type star, where would the LEAST light be detected from the system?
When the G star passes in front of the O type star
17. What is a visual binary? How do astronomers determine the orbital period of a visual binary?
A visual binary is seen as two distinct stars. The plan of the orbit can be at any angle to our line of sight.
What is meant by E = mc2? What do each of the terms stand for? In the reaction Hydrogen -> Helium + energy + ______, where does the energy come from? What tiny neutral particles are also created in this process (that go in the blank)?
Energy can become matter and matter can become energy. Neutrinos is the tiny neutral particles.
2. Is an F4 star hotter or cooler than an F5 star?
F4
How many protons (hydrogen nuclei) must come together to create helium? What force holds the protons together? How many protons define the element helium? What happens to the other protons?
Four protons must come together to create helium. Strong force is what holds the protons together. Two protons define the element helium.
How do astronomers determine the luminosity class of a star? What are the luminosity classes? If a star is designated as a B3III star, what does this mean? (be as specific as possible)
From the sharpness of the spectral line. Its spectral lines will be very broad/out-of-focus/smeared out looking.
Give a sentence to remember the order of the seven spectral types from hottest to coolest. Why is spectral type A not at the beginning? Why was it originally at the beginning of the list?
O,B,A,F,G,K, and M Oliver Beat Angela For Gay Kites Made
Where would you find an M-type GIANT star
On the right
What two forces balance to maintain the size of a main sequence star?
Gravity and thermal gas pressure are the two forces.
5. HD 25329 has a spectral type of K. Betelgeuse has a spectral type of M. Which is hotter?
HD is the hottest star because it is a type k which in the spectral type is the second coldest compared to Betelgeuse is type M and is the last in the spectral type which is the coldest.
What is the currently accepted energy source for the Sun and stars? How long can it last for a star like the Sun?
Hydrogen 10 billion
What observable property indicates how quickly a star is fusing hydrogen into helium?
Luminosity
What evolutionary events occur in a sun-like star from the original giant cloud to the end? How long does each phase take? How do astronomers observe these events?
Main sequence, hydrogen shell burning, helium to carbon, unstable helium fusion.
If an astronomer assumes that a G2 star is on the main sequence, but later finds out that it is, in fact, a giant star, will its apparent magnitude be different from the first assumption? If so, will the apparent magnitude be smaller or larger?
The absolute magnitude will be smaller
Why do O stars display weak hydrogen lines?
The Star O display weak hydrogen lines because they are really hot
2. How do astronomers determine the masses of stars? Draw an HR diagram indicating where the main sequence LOW mass stars and HIGH mass stars are.
Astronomers determine the mass of the stars by analyzing the orbit of binary stars
Where would you find a low temperature MAIN SEQUENCE star?
Bottom right
On your HR diagrams, where are stars of ... a.Low temperature? - Low absolute magnitude c. Low luminosity?
Bottom right -bottom left High left
How can astronomers determine the age of a star cluster from its HR diagram? What is meant by a "main sequence turn-off?"
By the amount of stars remaining on the main sequence. The point where stars turn off the sequence meaning their life ends
What happens to THE OUTSIDE of a star IMMEDIATELY after the core hydrogen fuel runs out? What eventually happens to it?
Immediately there is no sign but eventually the outer part will start to puff up and cool off
16. In cluster HR diagrams (e.g. the Pleiades, 47 Tuc, etc...), what value is plotted on the y-axis? Could you plot a useful HR diagram with random stars in the night sky using this value? Why or why not?
In a cluster diagram the apparent magnitude is on the y-axis. No you can't use a regular HR diagram because it has the absolute magnitude or the luminosity which is completely different. The clusters are all the same distance away.
Where would you find spectral type O MAIN SEQUENCE stars?
In the main sequence in the middle bottom left
11. If an astronomer assumes that a G2 star is on the main sequence, but later finds out that it is, in fact, a giant star, how does this affect the distance estimate for the star?
It will affect it in the way that it will be closer than previously thought.
What did Kelvin and Helmholtz think was the power source for the Sun and stars? How long would this last for a star like the Sun?
Kelvin and Helmholtz think that gravitational contraction was the power source for the Sun and stars. It would last between 10 - 100 million years
What holds up a normal, main sequence star against gravity? What holds up a white dwarf against gravity?
Radiation and heat is what holds the normal main sequence. Electron degeneracy pressure
1. What is a spectroscopic binary? How do astronomers determine the orbital period for a spectroscopic binary?
Spectroscopic binary is a shift of lines in the spectrum that indicates orbital revolution. Astronomers note the time it takes for the spectral lines to shift back and forth.
15. Star A has extremely strong, wide hydrogen lines. Star B has extremely strong, but narrow hydrogen lines. Which star is hotter? Which star is larger? Which star is more luminous? Explain your reasoning.
Star b is more luminous and larger
4. Why do M stars display weak hydrogen lines?
The M stars display weak hydrogen lines because they are really cool
