Astronomy Final

True or False: The Further away a Star is, the larger its parallax angle.

False

Roughly what is the age of the observable universe?

14 billion years

According to Newton’s theory of Gravitation, if you triple the distance between two masses, then the gravitational force between the two masses is…

weakens by a factor of 9

What do we mean by the Big Bang?

the event that marked the beginning of the expansion of the Universe

What is the ecliptic on the celestial sphere?

path that the Sun follows as the Earth orbits the Sun

What happens when a star establishes a stellar thermostat?

radiation pressure from nuclear fusion balances gravitational contraction

True or False: The Transit time of Venus across the Sun is the Smallest when the phase is full.

false

Electrons jumping from higher to lower energy levels is the origin of the…

lines in the absorption spectrum

Which of the following statements about our solar system is not correct:

Planets orbit the Sun with the same speed

Why are the terrestrial planets denser than Jovian planets?

Th Sun’s gravity pulled the denser material towards the inner part of the solar nebula, while the lighter gases escaped more easily to the outer part.

What drives the motion of continental plates on terrestrial planets?

convection cells in the mantle

Which internal energy source is of the most importance in continuing the heat of terrestrial planets today

radioactivity

Of the four gases, CO2, H2O, N2, and O2, which are greenhouse gases?

CO2 and H2O

Why do the moons show he same face to their planets?

it is explained by tidal forces from the planet acting on the moon

Which of the following is the correct luminosity - distance relation

(apparent brightness) = luminosity / (4*pi*(distance)^2)

What is the ultimate fate of a 20Msun star?

supernova and black hole

Which of the following is furthest from the Sun?

A comet in the Oort Cloud

According to nebular theory, what are asteroids?

They are the leftover planetesimals that never accreted into a planet because of the gravitational forces from Jupiter.

How do we know the magnetic field strength in sunspots?

Both first and second choices
(By measuring the amount of emission line splitting)

and

(By measuring the amount of absorption line splitting)

How does the Sun generate energy today?

nuclear fusion in the core

Which layer of the sun do we see?

Photosphere

Since all protostars have the same basic composition, what most determine how they differ?

location where they are born

How do main-sequence stars generate energy?

nuclear fusion of hydrogen to helium

Which of the following sequences correctly describes the stages of life of the low-mass star?

protostar, main-sequence, red giant, and white dwarf

What is a planetary nebula?

the expanding shell of gas that is no longer gravitationally bound to the remnants of a low-mass star

Where is our solar system located in the Milky Way Galaxy?

in the galactic disk roughly halfway out from the galactic center

What makes up most of the mass of the milky way?

Stars and dust in the spiral arms of galactic disk

True or False: A flat rotation curve (out to the edge of the galaxy) indicates the existence of constant mass (out to the edge of the galaxy)

True

True or False: Because the atomic mass composition of the Universe is 75% hydrogen and 25% helium no matter which way we look, the Universe must have been hot enough to fuse hydrogen and helium

True

True or False: The observable Universe is the same size today as it was several billion years ago

False

What is the more accurate method of measuring very large distances (out to the edge of the Universe)

White Dwarf Supernovas

True of False: The Big Bang Theory predicts a uniform cosmic thermal radiation spectrum that has been red shifted from gamma rays towards microwave wavelengths

True

True or False: Dark Matter is probably made of particles like protons, neutrons and electrons

False

What type of stars end their lives as supernovae?

stars that are at least several times the mass of the Sun

After a supernova event, what is left behind?

Either a neutron star or a black hole

What is Hubble’s Law?

The recession velocity of a galaxy is directly proportional to its distance from us

Why can’t we see past the cosmological horizon?

Beyond the cosmological horizon, we are looking back in time before the Universe as formed

What defines the habitable zone around a star?

The region around a star where liquid water can potentially exist on a planet’s surface

True or False: If the expansion of the Universe is accelerating, is has less tan a critical mass and it will expand forever.

True

How far would a radio message which sent out from Earth in 1980, have gotten?

A very small fraction of the Milky Way’s radius

We can study how galaxies evolve because…

the further in distance we look, the farther back in time we see

What do we mean by “Dark Energy?

the agent causing the accelerated expansion of the Universe

What is the meaning of the word cosmos?

the total of matter and energy within and between galaxies

Why are Cepheid stars so important for measuring astronomical distances?

their luminosity can be calculated from the period and hence can be used as standard candles

What evidence do we have for the existence of black holes?

Gravitational interaction with other astronomical objects

What is the temperature of the present universe?

3°K

What is meant by “dark energy”?

the agent causing the universal expansion to accelerate

Which of the following is not evidence for dark matter?

the expansion of the universe

I observe a galaxy that is 100 million light-years away: what do I see?

the light from the galaxy as it was 100 million years ago and it is redshifted

Why are Cepheid Variables important?

Cepheid are pulsated variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as “standard candles” for distance measurements