UO ASTR 123 Chapters 7-8 Review

Roughly what percent of the mass and energy contents of the universe is made up of ordinary (atomic) matter?

5%. All matter (dark + visible) makes up 28%. 23% of that 28 is made up of dark matter.

What is inflation?

At some point the universe expanded super rapidly (less than one second).

If the universe consisted only of matter and its density were equal to critical, the universe would

Continue expanding, eventually showing down to zero.

What is the universe doing as it expands?

Cooling off

What are the 3 pillars of cosmology?

Cosmo redshift (THE EXPANSION OF SPACE), Cosmic Microwave Background, Big Bang Nucleosynthesis

What dominates overall energy density?

Dark Energy

No nuclei beyond H can from before what?

Deuterium

When the age of the universe was about 10 seconds, it had cooled sufficiently for neutrons and protons to bind together and form the key nuclear species which allows production of helium to proceed. This key nucleus is called

Deuterium - couldn't form until the universe was 10 sec old.

What is the horizon problem?

Different regions of the CMB are in thermal equilibrium even though they aren't connected.

Why did Einstein introduce the cosmological constant into the equations of his General Theory of Relativity when describing the universe?

Einstein's equations required the universe to expand or contract and he couldn't accept either one. The cosmo contant stops either. (The big blunder)

Where did the expansion of the universe begin?

Everywhere all at once

Based on CMB data, the average density of the universe is?

Exactly equal to the critical density

How does inflation solve the flatness problem?

Gigantic and rapid inflation causes the small portion of the universe that we can see to appear flat because it is so large. (Like a zoomed in pic of a super inflated balloon)

What is the problem with the Hubble Constant?

Measurements of it do not agree.

What did big bang nucleosynthesis create?

Most of universe's helium, small amounts of deuterium, and lithium

At 380k years after the Big Bang, electrons and protons are cool enough to allow what to form?

Neutral Hydrogen

Is anti-matter a candidate for the identity of Dark Matter?

No

Does the rate of cosmic ray showers provide evidence for DM?

No it doesn't. The rotation curves of stars moving around galaxies, large scale structure of galaxies and galaxy clusters, analysis the mass of gravitational lenses, and merging galaxy clusters such as the "bullet cluster" do however provide evidence.

Could inflation ever be directly observed?

Potentially with gravitational waves

Protons and Neutrons are composed of more elementary particles called:

Quarks

How was CMB radiation first discovered?

Scientists from Bell Labs were trying to use microwaves for communication and kept picking up some static in the background.

What did not occur in the first few minutes after the big bang?

Star formation

What is critical density?

The average density of matter required for the universe to halt its expansion. Mass/energy density = critical density

What is the flatness problem?

The density of the universe is flat, which requires it to be at critical density. Which contradicts big bang cosmology that argues curvature grows with time.

Why do older galaxies (that we view as younger) appear redder and smaller

The expansion of the universe has caused a redshift in the lookback time.

Why did nucleosynthesis stop when the universe was about 3 minutes old?

The universe was cooling too fast to produce elements beyond helium

What is the Big Crunch?

The universe will reverse its expansion because the density of it's matter will cause gravity to pull it back together.

Is there more matter or antimatter?

They should be equal but there is more matter.

How does inflation solve the horizon problem?

Two regions could've been together but when the universe 'inflated' rapidly making these regions separate from our perspective.

How does gravity have to do with our detection of Dark Matter?

We can detect Dark Matter's gravity

What is a cosmic ray shower?

When high-energy particles originating from the sun, or areas outside our galaxy, rain down into the atmosphere.

The expansion of the universe is

accelerating

The universe's geometry is

flat as shown by measurements of the CMB

What do the surveys of the three-dimensional distribution of groups of galaxies reveal about how groups and clusters of galaxies are organized?

galaxy groups are organized into huge filaments with great voids between them. This is due to dark matter.

How does a period of extremely fast inflation very early in the history of the universe explain the observation that the geometry of the universe looks flat (not curved) to us?

inflation increased the size of the universe so much that the resulting universe looks flat from any point of view

According to the Cosmological Principle, the universe

is isotropic and homogeneous over large distances, meaning if you look out into the universe in any large distance, it will more or less look the same

Which of the following does NOT happen when two galaxies collide?

many of the stars in one galaxy collide with the stars in the other. (Grapefruit example)

The huge amount of inflation means that

quantum fluctuations could have expanded to create the over/under densities observed in the CMB

Galaxies that we see as they were 11 billion years ago or more, as compared to galaxies today, are generally:

redder and smaller

The "horizon problem" is illustrated by what observation of the cosmic microwave background (CMB)?

that the temperature of disconnected regions is almost exactly the same

How do astronomers currently think the amount of detectable (observable) matter in the universe compares to the amount of dark matter?

the amount of detectable matter is about 1/5th the amount of dark matter

The redshift observed in the light emitted by distant galaxies is due to

the expansion of space

With enormous effort, a team of astronomers manages to collect enough light from a galaxy far, far away to produce a spectrum. That spectrum has lines from the elements carbon, silicon, and sulfur. This tells the team that

the galaxy must have had an entire generation of stars that was born, lived, and died. This is evident because elements such as carbon were not created in the super early stages of the universe

The model of the universe that involves an enormous increase of size during a very short time in the early universe is called:

the inflationary universe model

What has lead astronomers to believe that the universe is expanding?

the measurement of galaxy distances using Type Ia supernovae

In the observation of galaxies, astronomers refer to look-back time, which means

the time it took for the observed light from a galaxy to reach us

If the universe is flat

then density must be critical

The observed cosmic microwave background (CMB) is extremely uniform. What is the significance of the small deviations from uniformity which show up as red or blue regions in the CMB images?

they seed the large scale structure in dist. of galaxies we observe today

What other (not currently observed) isotopes were formed in the Big Bang?

tritium and lithium-7

About how old in the universe?

~13.8 billion years.