Chapter 13 PT 1

Question 1

How are stars born?

Answer 1

A star is born when gravity causes a cloud of interstellar gas to contract to the point at which the central object becomes hot enough to sustain nuclear fusion in its core.
(Stars are born in cold, dense clouds of gas whose pressure cannot resist gravitational contraction.)

Question 2

What are main sequence stars?

Answer 2

Stars whose temperature and luminosity place them on the main sequence of the H-R diagram. Main-sequence stars release energy by fusing hydrogen into helium in their cores.

Question 3

main-sequence turnoff point

Answer 3

The point on a cluster’s H-R diagram where its stars turn off from the main sequence; the age of the cluster is equal to the main-sequence lifetime of stars at the main-sequence turnoff point.

Question 4

main-sequence lifetime

Answer 4

The length of time for which a star of a particular mass can shine by fusing hydrogen into helium in its core.

Question 5

main sequence

Answer 5

The prominent line of points (representing main-sequence stars) running from the upper left to the lower right on an H-R diagram.

Question 6

What Causes The Red Giant Stage

Answer 6

when the Sun’s core hydrogen is finally depleted, nuclear fusion will cease. With no fusion to replace the energy the star radiates from its surface, the core will no longer be able to resist the inward pull of gravity, and it will begin to shrink. After 10 billion years of shining steadily, the Sun will enter an entirely new phase of life.

Question 7

What Occurs During The Red Giant Stage

Answer 7

outer layers will expand outward

Question 8

How are white dwarfs created

Answer 8

Low-mass stars like the Sun leave behind white dwarfs when they die.

Question 9

What is a white dwarf?

Answer 9

Exposed core of a star that has died

Question 10

What causes a white dwarf novae

Answer 10

When the temperature at the bottom of the layer reaches about 10 million K, hydrogen fusion suddenly ignites.

Question 11

What causes a white dwarf supernovae

Answer 11

white dwarf limit will explode completely in a white dwarf supernova.

Question 12

What does the big bang predict?

Answer 12

that the radiation that began to stream across the universe at the end of the era of nuclei should still be pres-ent today
that some of the original hydrogen in the universe should have fused into helium during the era of nucleosynthesis.

Question 13

Evidence of Big Bang

Answer 13

“noise” from the Bell Labs antenna was the predicted cosmic microwave background

Question 14

What is cosmic microwave background

Answer 14

The remnant radiation from the Big Bang, which we detect using radio telescopes sensitive to microwaves (which are short-wavelength radio waves)

Question 15

How was cosmic microwave background discovered

Answer 15

Arno Penzias and Robert Wilson, two physicists working at Bell Laboratories in New Jersey, were calibrating a sensitive microwave antenna designed for satellite communications
kept finding unexpected “noise” in every measurement they made. The noise was the same no matter where they pointed the antenna

Question 16

What is Obler’s Paradox

Answer 16

A paradox pointing out that if the universe were infinite in both age and size (with stars found throughout the universe), then the sky would not be dark at night.

Question 17

What is Cosmological Principle

Answer 17

The idea that matter is distributed uniformly throughout the universe on very large scales, meaning that the universe has neither a center nor an edge.

Question 18

What is the Fate of the Universe?

Answer 18

If dark energy is indeed what’s driving the acceleration of the universe’s expansion, then we expect the expansion to continue accelerating into the future, as long as the effects of dark energy do not change with time and there are no other factors that affect the fate of the universe.

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