Unit 3 (Chapters 8-11) Flashcards

Question

What is spectroscopic parallax?

Answer 1

This is when you find a stars distance based on spectral type, luminosity class, and apparent magnitude. The spectral type tells you the horizontal location on the HR diagram. Luminosity class gives you approximate vertical position. Plotting these two points gives you absolute magnitude which can then be used in a formula with apparent magnitude to determine distance.

Answer 2

Binary stars are pairs of stars that orbit each other. Types: - Visual binary systems: stars are visibly separate and their orbit can be physically observed - Spectroscopic Binary Systems: stars are too close together, they can only be discerned through the spectral light - Eclipsing binary systems: a spectroscopic binary system whose orbit is nearly on the edge to earth so they eclipse each other as they orbit and you can see the difference in brightness when one star is eclipsed.

Answer 3

The orbital period and size of the orbit tells you the amount of gravitational force being exerted on the stars which in turn tells you about the star's mass.

Answer 4

Red dwarfs with low luminosity Most of the stars we can actually see are not typical but rather just more visible because they are so luminous.

Answer 5

Main sequence stars follow a mass-luminosity relation where high mass = high luminosity. This ONLY works in main sequence stars.

Answer 6

Main sequence stars have similar density to the sun Giants are low density Supergiants are extremely low density White dwarfs are extremely dense

Answer 7

Interstellar Medium is the gas and dust between stars. Nebulae are clouds of gas and dust scattered throughout the sky. There are three types: 1. Emission Nebula: when a hot star excites the gas near it to produce an emission spectrum. This ISM forms B1 or hotter stars. This ISM has a density of 100-10000 atoms/m^3 2. Reflection Nebula: this nebula scatters starlight due to its dust content. the spectrum for this star is the same as the star's light being reflected. 3. Dark nebula: dense clouds of gas and dust which block the view of more distant stars. They have irregular shapes which suggests that there a breezes and currents in the ISM 2.

Answer 8

Mostly hydrogen, some helium, and 2% other heavier elements . The ISM is 99% gas and 1% dust with the dust being made up of: - Carbon -Silica - Iron - ice/organic components

Answer 9

This is when far away stars appear more red than they should because the blue shorter wavelengths are scattered more readily by the ISM so a larger portion of red wavelengths reach earth.

Answer 10

VERY COLD, 100K (280F) or lower

Answer 11

1. Cool Clouds (H-I clouds): density of 100 atoms/cm^3, is non-ionized, is 100K in temp, and often 50-150 parasec (pc) in size. 2. Intercloud medium: hot low density gas that fills the space between cool clouds. Temperature is a few 1000k, density 0.1atom/cm^3), partially ionized. Has the same pressure as cool clouds so they co-exist without encroaching on each others region. 3. Molecular clouds: Clouds of gas and dust with densities ranging from 100-1000atoms/cm^3. Molecules form inside these clouds because they are protected from UV rays by the dust. Usually are only a few hundred solar masses BUT giant molecular clouds can be up to 1 million solar masses (Giant molecular clouds are where stars form). 4. Coronal Gas: has high temperature and low density. Temp = 10^6K but a density of 10^-4 particles/cm^3. they are the same pressure as cool clouds so they do not encroach on their region. Form from the death of a star and can force cool gas to compress and form stars.

Answer 12

about 50% intercloud medium, 20% cool clouds, 20% molecular clouds, and 10% coronal clouds.

Answer 13

1. Thermal Energy: thermal energy causes clouds to expand and gravity must be stronger than this outward force 2. Magnetic fields: magnetic fields in ISM act as an internal spring to stop the gas from contracting, gravity must be stronger than this. 3. Rotation: as the rotating gas contracts, it rotates fast and can counteract the gravity, resisting contraction. 4. Turbulence: the turbulent, twisting distorted nature of the gas is caused by a strong current that the gravity has to overpower.

Answer 14

A dense core is when regions in the giant molecular cloud begin to contract. They are caused by shock waves (which are common) and dense cores are dense enough that gravity becomes able to overcome the 4 factors which normally prevent it from compressing the cloud.

Answer 15

This is when the dense cores contract, gravity draws the atoms towards the centre. As the atoms fall they gain speed and collide with each other, randomizing their movement. This rapid random movement creates thermal energy which begins to heat the cloud. It is through this process that gravitational energy is converted to thermal energy. (the reverse can also happen where atoms move more, they lose speed, and the gas cools.)

Answer 16

A protostar is a forming star that is compressed enough to be opaque at all wavelengths but not hot or compressed enough to generate energy by nuclear fusion. Cocoon nebula is the cold dusty gas that surrounds the contracting protostar and absorbs the protostar's radiation.

Answer 17

The more massive the star, the stronger its gravity and therefore the more rapid it contracts. For example, the sun took about 30 million years to get from cloud to main sequence where as a 30 solar mass star would only take 30 000 years

Answer 18

Young Stellar object is a star late in the stages of formation. The birth line is the location on an H R diagram where the protostar becomes detectable at visible wavelengths.

Answer 19

these are rapidly spinning cores in the cloud that flatten like a spinning pizza dough. The angular momentum leads to gas being added to the centre allowing the protostar to grow. These disks cause bipolar flow which push into ISM and produce glowing globs called Herbig-Haro objects.

Answer 20

An association is a widely distributed star cluster that is not dense enough to be permanently held together by its own gravity so the stars wander.

Answer 21

This is a balance created by the gravity of the star working to make it contract and the internal pressure working to make it expand.

Answer 22

CNO cycle where carbon is converted to nitrogen and then to oxygen and then to helium. This cycle is often used in O and B stars.

Unit 3 (Chapters 8-11) Flashcards

(46 cards)