11B.2 Stellar classification

Question 1

what have Astronomers done with stars

Answer 1

they have classified stars into groups according to their temperature, as it determines the spectral output of the star, and it can also suggest its chemical composition and age

Question 2

what is the order of spectral star classes from hottest to coolest

Answer 2

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Question 3

the hotter the stars are

Answer 3

the more mass and more luminous they are, and that is because their is a large gravitational pressure at the centre of a massive star which makes the nuclear fission within the star very fast, producing loads of energy and using the hydrogen fuel in the star at a very high rate (so luminosity). In addition the massive stars and very large large. (so mass)

Question 4

what do the white lines in the light spectra show

Answer 4

the position of absorption lines, which give us information about the chemical composition of the star, and the doppler shift which tells us their velocity

Question 5

if we combine light with equal intensity of thee visible spectrum we will make

Answer 5

white light

Question 6

what is the Hertzsprung-Russel diagram

Answer 6

a plot of stars, showing luminosity(or absolute magnitude) on the y-axis, and the temp(or spectral class) on the X-axis

Question 7

the temp measurements of stars from the Hertzsprung-Russel diagram is considered to be

Answer 7

that the star is considered to be a black body

Question 8

the luminosity measurements form the Hertzsprung-Russel diagram are

Answer 8

not that accurate since measuring distances if from the star to earth isn’t completely accurate

Question 9

what is the main sequence

Answer 9

a diagonal line form the top left to bottom right of a Hertzsprung-Russel diagram which marks stars that are in a generally stable phase of their existence

Question 10

what is also seen on the Hertzsprung-Russel diagram

Answer 10

white dwarfs bottom right, red gaint on the top left with red supergiant on tope of it

Question 11

what is also seen on the Hertzsprung-Russel diagram

Answer 11

white dwarfs bottom right, red giant on the top left with red supergiant on top of it

Question 12

why are some stars more polluted in the Hertzsprung-Russel diagram compared to others

Answer 12

because some stars have a very shorter life spam so their isn’t many of them to see, that’s why the tope left and the bottom right of the main sequence isn’t as populated as the middle

Question 13

what are the two elements that stars are originally made form

Answer 13

hydrogen, and helium

Question 14

what is a protostar

Answer 14

a mass of dust and gas clumping together under the force of gravity prior to the start of nuclear fission within its core, which will go on to become a star

Question 15

what is a neutron star

Answer 15

one of the possible conclusions to the life of a large mass star. it is a very small and dense, and it is composed of neutrons

Question 16

what is a black hole

Answer 16

one of the possible conclusion to the life of a large mass star. a region of space-time in which gravity is so strong preventing anything from escaping it including EM radiation

Question 17

how does nuclear fission release energy

Answer 17

the energy difference between the nuclei before and after fusion means energy release often as EM radiation to heat the star

Question 18

how does a star not collapse on it self due to gravity

Answer 18

the force of gravity is going against the outward pressure made from nuclear fission (EM radiation)

Question 19

What is the low mass star life cycle

Answer 19

so first is the protostar, after that the hydrogen atoms start boning to form helium atoms forming a main squence

Question 20

What is the low mass star life cycle

Answer 20

so first is the protostar, after that the hydrogen atoms start boning to form helium atoms forming a main sequence, at this stage the radiation pressure outward, and the gravity force inward are at equilibrium, eventually the star will run low of hydrogen fuel, but will have produced so much more energy that it will slightly expand, this expansion will cause the temp to fall and to form a red giant, then after most of the hydrogen fuel has been used and the star will start fussing helium nuclei, this complex process can cause an explosion which throws materials from the star into space, then this will form a planetary nebula, as the fuel runs out the outward pressure drop causing the star to collapse on its self forming a white dwarf as heat would increase. as time continues the white dwarfs energy will will run out and it will die making it pass through a red drawf then a black dwarf

Question 21

what is a planetary nebula

Answer 21

the remains of an explosion at the end of a low-mass star. materials that may eventually join together into new planets

Question 22

what is a black dwarf

Answer 22

it is the final stage of a low-mass star, when nuclear fission has ceased and it cooled down so it no longer emits visible light

Question 23

what is the massive stars life cycle

Answer 23

so first is the protostar then the hydrogen would react together to form a blue super giant at this point the outward radiation and the force of gravity inward are at eq, once most of the hydrogen as been used up a lot of energy releases at that expands the star causing it to form a red super giant dropping the energy down, but since the massive starts have much more larger energies fusion between nuclei larger than He starts forming elements which are multiple of fours like carbon, oxygen and silicon, once all of the nuclei has fused to form iron(which is the highest nuclei that can be made with the energy provided) the outward radiation would drop causing the star to collapse on its own, this sudden large collapse produces a large burst of energy in the supernova explosion, this releases so much energy that all the elements within our universe are produced, after the supernova the entire star may be completely shattered, but if there is a central core of stellar matter it would form a neutron star or if big enough a black hole

Question 24

why is neither the black dwarf nor the neutron star, nor the black hole plotted on the Hertzsprung-Russel diagram

Answer 24

because they are hard to spot since they emit to light as will as the black dwarf so far is only theoretical as there hasn’t been time for any to develope