Physical Science Module 16

Front 1

Are most stars in a single or multiple star system?

Back 1

Most stars are in a multiple star system.

Front 2

What is the sun composed of?

Back 2

74% hydrogen gas, 25% helium gas, and trace other elements.

Front 3

What are the four regions of the sun?

Back 3

Core, radiative zone, convection zone, and photosphere.

Front 4

What happens in the core of the sun?

Back 4

Trememdous pressure causes nuclear fusion, in which a hydrogen-1 nucleus fuses with a hydrogen-2 nucleus to form helium-3 plus energy.

Front 5

How are energy and mass related?

Back 5

energy = mass x the speed of light squared.

Front 6

What happens to the energy produced by nuclear fusion in the sun's core?

Back 6

Some of it helps maintain the core's 27 million degree temperature, but most of it is sent out as light (photons) and passes into the radiative zone.

Front 7

What happens to photons in the radiative zone?

Back 7

Photons bounce around off the tightly packed gases, eventually making it out to the convection zone.

Front 8

What happens to photons in the convection zone?

Back 8

They are absorbed by gases. The extra energy makes the gases rise up toward the photosphere. There they give the energy to gases in the photosphere, then sink back down to the bottom of the zone to pick up more photons and start the process over again.

Front 9

What happens in the photosphere?

Back 9

Gases are heated up by energy transfer from the convection zone. They then rise to the top of the layer, and give off the extra energy as electromagnetic waves.

Front 10

Why does the sun not appear uniform?

Back 10

The sun's magnetic field strongly influences the photosphere, causing arcs, sunspots, and solar flares. How, exactly, we do not understand.

Front 11

What is a solar flare?

Back 11

It is an intense variation in the brightness of the photosphere, and results in an enormous amount of energy being sent out toward earth. This can interfere with satellites, radio, and power grids.

Front 12

How do the sun's solar flares compare with other star's?

Back 12

They are very mild. The solar flares that occur periodically on similar-sized stars would destroy life on earth.

Front 13

Nuclear fusion

Back 13

The process by which two or more small nuclei fuse to make a bigger nucleus. This is how the sun produces energy.

Front 14

Nuclear fission

Back 14

The process by which a large nucleus is split into smaller nuclei. This is how people produce nuclear power.

Front 15

Chain reaction

Back 15

A situation where one nuclear fission reaction produces multiple free neutrons, which go on to trigger multiple more nuclear fission reactions.

Front 16

critical mass

Back 16

The amount of isotope necessary to sustain a chain reaction.

Front 17

What happens when there is significantly more than a critical mass of a large nucleus present?

Back 17

The chain reaction can grow out of control, causing an explosion.

Front 18

What happens when there is just a bit more than a critical mass of a large nucleus present?

Back 18

A chain reaction is sustained, but doesn't get too big. This produces a lot of heat, but not an explosion.

Front 19

What are the positive points about nuclear fission?

Back 19

The fuel is cheap and last a long time.

Front 20

What are the negative points of nuclear fission?

Back 20

Meltdowns can occur and the byproducts are radioactive.

Front 21

What is a meltdown?

Back 21

Actual physical melting of the reactor, which can occur if the chain reaction is not controlled carefully, causing release of the radioactivity into the atmosphere.

Front 22

Are other methods of energy production dangerous and polluting?

Back 22

Yes. Coal mining is dangerous to people's health and the burning of coal causes pollution.

Front 23

Why don't we use nuclear fusion for power production?

Back 23

It would be wonderful, as it has no radioactive byproducts and can be stopped quickly so that there would be no meltdowns, but we can't do it efficiently enough at the present time. More energy is consumed than produced with current technology.

Front 24

What is a star's color related to?

Back 24

It is related to the star's temperature. Red stars are coolest, yellow are middle, and blue stars are hottest.

Front 25

How is a star's temperature designated?

Back 25

By a spectral letter. In order from coolest to hottest, M,K,G,G,A,B,O.

Front 26

absolute magnitude

Back 26

The brightness of a star, corrected for distance, on a scale of -8 to +19. The smaller the number, the brighter the star.

Front 27

apparent magnitude

Back 27

The brightness of a star as seen in the night sky. The smaller the number, the brighter, the star.

Front 28

H-R Diagram
Hertzsprung-Russell Diagram

Back 28

A diagram that plots the temperature of a star against the brightness of a star. The hottest, brightest stars are in the upper left and the coolest, dimmest stars are in the lower right corner.

Front 29

main sequence star

Back 29

A star in which there is a strict relationship between mass, brightness, and temperature. The larger the star, the brighter and the hotter it is. 90% of stars fall in this category, including the sun.

Front 30

white dwarf

Back 30

The second most common group of stars. They are have a high absolute magnitude (so they are dim), they are small, but they are incredibly massive (therefore the white, hot name.)

Front 31

red giant star

Back 31

Huge stars that are cool (red) but bright. Despite the fact that they are cool overall, their cores are very hot due to the massive pressure from their size. This results in a cool, but bright star. The nuclear fusion in a red giant core combines three helium atoms to make a carbon atom.

Front 32

supergiant star

Back 32

The largest stars in the universe. Because of this mass, they are also bright (more pressure in the core to make photons.) This is the rarest type of star.

Front 33

What is a variable star, and what are the two types of them?

Back 33

A variable star has a constantly changing magnitude or brightness. The two types are novas and pulsating variables.

Front 34

Nova

Back 34

The result of an explosion in a star, which temporarily increases its brightness. With each explosion, a small part of the star's mass is used up.

Front 35

supernova

Back 35

An extreme version of a nova. In a supernova, the star truly explodes, making a huge flash then fading away.

Front 36

nebula

Back 36

A cloud of bright gases that remains after the explosion of a supernova.

Front 37

pulsating variable

Back 37

Stars that expand and contract, changing its brightness as it does. It does not lose any of its mass as it does so. Many of them do so on a regular basis.

Front 38

Cepheid variable

Back 38

Pulsating stars between 5 to 20 times as massive as the sun. They expand/contract on a very constant basis. They are used to measure the distance to far away stars.

Front 39

binary star

Back 39

two start that are close enough to orbit each other.

Front 40

eclipsing binary star

Back 40

binary stars that are oriented such that they regularly eclipse each other from our viewpoint, resulting in a star that seems to be variable, but really isn't.

Front 41

parallax method

Back 41

Method using geometry to measure the distance to stars that are reasonably close to earth. It is very exact, but can't be used for stars that are far away.

Front 42

apparent magnitude method

Back 42

A method that uses the predictability of a Cepheid variable star's pulsation and its known relationship to the apparent magnitude of the star to measure the distance to adjacent distant objects.

Front 43

Light year

Back 43

The distance light could travel along a straight line in one year.

Front 44

galaxy

Back 44

A large ensemble of stars, all interacting through the gravitational force and orbiting around a common center.

Front 45

What are the three types of galaxies?

Back 45

spiral, elliptical, and lenticular

Front 46

Where is the earth located?

Back 46

It is on the inner edge of the Orion arm of the Milky Way Galaxy in the Local Group, which is on the outer edge of the Virgo Cluster.