Astro 311 - Midterm

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The distances to bodies in the solar system are a few light minutes to light hours (T or F)

True

Which of the choices below correctly lists things in order from largest to smallest?
- local group, universe, milky way, solar system

Universe, Local Group, Milky Way, Solar System

It was Aristotle who used the scientific method to show the Earth was a sphere. (T or F)

True

Aristotle's hypothesis was that:

only a spherical Earth would always cast a circular shadow on the Moon

Constellations are close clusters of stars, all at about the same distance from the Sun. (T or F)

False

Only at the equator are all the stars visible over the course of the year. (T or F)

True

Over the course of a night, Polaris moves less than any other visible star in the sky. (T or F)

True

There are 3,600 arc seconds in a degree. (T or F)

True

A star with a right ascension of 2.6 hrs will cross the local meridian from east to west 2.6 hours after the vernal equinox. (T or F)

True

About how many stars are visible on a clear, dark night with the naked eye alone?
- millions - tens of thousands - a few thousand - a few dozen - a few hundred

A few thousand

Into how many constellations is the celestial sphere divided?

88

What are constellations?

Groups of stars making an apparent pattern in the celestial sphere

Where on Earth would you be if Polaris was at your zenith?

North Pole

Where on Earth can you observe all the stars in the sky over an entire year?

Equator

The parallax shift of a star would be greater if viewed from Mars than from Earth.

True

The star Wolf 1061 has a parallax of 2.34 arcseconds, while the star Ross 652 has a parallax of 1.70 arcseconds. What can you correctly conclude?

Wolf 1061 must have a larger proper motion than Ross 652.
Wolf 1061 is closer to Earth than Ross 652.
Both stars are outside the Milky Way galaxy.
Ross 652 is closer to Earth than Wolf 1061. Ross 652 must have a larger proper motion than Wolf 1061.

Wolf 1061 is closer to Earth than Ross 652.

Which of the following describes parallax?
It is only applicable to objects within the solar system.
It was first observed by Galileo with his new telescope.
It is inversely proportional to the distance to the star.
It is more accurate as the distances to objects becomes greater.
It is best measured over exactly one year intervals.

It is inversely proportional to the distance to the star.

A star with a large parallax is .... from earth

a short distance

If a star rises about 9 PM tonight, and with the sidereal day being four minutes less than the solar one, then in a month it will rise about 7 PM. (T or F)

True

The place the Sun stops its northward motion along the ecliptic is the:

Summer Solstice

The places where the Sun crosses the equator are called the:

Equinoxes.

A year is defined as

the time it takes for Earth to complete an orbit around the Sun.

The Earth's circumference was first determined by:

Erastothenes with solstice shadows.

From the South Pole, Polaris would appear directly overhead. (T or F)

False

Given that the planet orbiting the nearby star 51 Pegasi is about larger than the Earth, but more massive, on that world you would weigh:

the same as you do here

The force of gravity between two objects: (in the context of mass and distance)

increases with the masses of the bodies, but decreases with the square of the distances between them.

Which of these was a contribution of Newton to astronomy?
The Moon pulls as strongly on us as we do on it.
The Sun's gravity is greatest on a planet at perihelion, so the planet must speed up.
Artificial satellites could be put into orbit about the Earth.
His differential calculus lets us calculate planetary motions more accurately.
All of these were due to Newton's work.

All of these were due to Newton's work

Combining Newton's and Kepler's laws, we can weigh the Sun, provided we know:
its density as found by spectroscopy.
the exact timings of the transits of Venus and its diameter
the Earth's mass and circumference.
the size of the A.U. and exact length of the year.
its temperature as found by Wien's Law.

the size of the A.U. and exact length of the year.

A sound wave moving through water has a frequency of 256 Hz and a wavelength of 5.77 m. What is the speed of sound in water?

v= 1480 m/s

Radio waves, visible light, and x-rays are all a type of electromagnetic radiation. (T or F)

True

The frequency of a water wave gives us its height (T or F)

False

A change in a visible light wave's amplitude would be viewed as a change in its colour (T or F)

False

As white light passes through a prism, the red (longer) wavelengths bend less than the blue (shorter) wavelengths, so forming the rainbow of colors (T or F)

True

Wave energy can only be transmitted through a material medium. (T or F)

False (no medium in space)

Which of these is constant for ALL types of electromagnetic radiation in a vacuum?
velocity
frequency
photon energy
amplitude
wavelength

velocity

Light that has all the electrical fields vibrating in the same plane is said to be ________

polarized

Compared with ultraviolet radiation, infrared radiation has a greater...

wavelength

What does the phenomenon of interference demonstrate?

wave nature of light

Which form of electromagnetic radiation is absorbed by carbon dioxide and water vapor in our atmosphere?

infrared

X-ray telescopes are located in orbit around the Earth because...

x-rays don't reach earth

Which type of radiation can be observed well from Earth's surface?

visible

According to Wien's law, the hottest stars also have

the shortest peak wavelength.

The Fraunhofer lines in the solar spectrum are actually:

absorption lines due to the thin outer layer above the photosphere.

The Orion Nebula, M-42, is a hot, thin cloud of glowing gas, so its spectrum is:
a few bright lines against a dark background.
a few dark line in the continuum.
a continuum, strongest in the color red.
a continuum, but with both bright and dark lines mixed in.
not in the visible portion of the spectrum.

a few bright lines against a dark background.

Which of the electromagnetic radiation types has the lowest energy?

radio

Why are molecular lines more complex than elemental spectral lines?
Molecules are heavier than atoms.
Molecules have two or more atoms.
Most of the universe is made of molecules, not individual atoms.
Molecules are the basis of life.
Molecules can vibrate and rotate as well.

Molecules can vibrate and rotate as well

The Doppler effect can reveal the rotation speed of a star by the splitting of the spectral lines. (T or F)

True

What is the primary purpose of an astronomical telescope?

to collect a lot of light and bring it in into focus

Which type of telescope has the simplest light path?

prime focus reflector

What is the light-gathering power of an 8 inch telescope compared to a 4 inch telescope?

4× better

What is the resolving power of the telescope?

the ability to distinguish adjacent objects in the sky

Diffraction is the tendency of light to:

spread around corners.

One advantage of the Hubble Space telescope over ground based ones is that...
in orbit, it can operate close to its diffraction limit at visible wavelengths.
it can better focus x-ray images.
it is larger than any Earth-based scopes.
its adaptive optics controls atmospheric blurring better.
it can make better observations of the ozone layer.

in orbit, it can operate close to its diffraction limit at visible wavelengths.

What problem is adaptive optics designed to correct?

the effects of atmospheric turbulence

Which of the following is a problem inherent in all large radio telescopes?

The dust clouds in the Milky Way block almost all wavelengths except light.
They are badly affected by poor seeing and atmospheric turbulence.
Their waves are blocked by water vapor, so they must be located in deserts.
The lightest breeze shakes them, making the observations blurry.
Radio waves have long wavelengths, so radio telescopes have poor resolution.

Radio waves have long wavelengths, so radio telescopes have poor resolution.

The design of modern x-ray telescopes depends on

grazing incidence optics.

At very large distances from the Sun, its corona turns into the solar wind. (T or F)

True

A sunbather on the clear day is receiving about 500 watts of solar power. (T or F)

True

The luminosity of the Sun is a measure of

the total energy emitted by the Sun in all directions.

Hydrostatic equilibrium in our Sun is the balance between

gravitation and pressure.

In the proton-proton cycle, you must first make deuterium, then helium. (T or F)

True

The speed of light is 3.00 × 108 m/s. If 2.00 kg of mass is converted to energy, how much energy will be produced?

1.80 × 1017 J

The nearest star to our Sun, Alpha Centauri, is still over a parsec distant. (T or F)

True

The proper motion of a star is its true velocity through space. (T or F)

False

Star A and star B have the same apparent magnitude. Star A is twice as distant as star B. Therefore, star A has twice the luminosity as star B. (T or F)

False

Star A has an abosolute magnitude of 2.5 and star B has an apparent magnitude of 2.5, but star A is a main sequence star and star B is a red giant. Which statement below is correct?
Star A and star B appear to have the same brighntess, but actually star A is brighter than star B.
Star A and star B appear to have the same brightness, but actually star B is brighter than star A.
It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.
Star A appears brighter than star B, but actually star B and star A are the same brightness.
Star B appears brighter than star A, but actually star B and star A are the same brightness.

It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

A type B9 star is hotter than a type A0. (T or F)

True

What physical property of a star does the spectral type measure?

Temperature

The most famous G type star is:

the sun

Compared to the size of the Sun, between what range of sizes are most stars found?

0.01 to 100 solar radii

On the H-R diagram, most bright naked eye stars would lie at the ________

top left

On the H-R diagram, white dwarfs lie Sirius B and Procyon B lie...

at the lower left

Having nothing to do with trigonometry, ________ parallaxes use the width of absorption lines to estimate the star's luminosity and size and distance.

spectroscopic

Eclipsing binaries are the most useful, giving us sizes as well as masses of the pair. (T or F)

True

In a spectroscopic binary system, the star showing the larger blue shift is:

less massive and approaching us at this moment

What is the typical main sequence lifetime of a M-type star?

a trillion years

What is the typical main sequence lifetime of a B-type star?

20 million years

Some regions along the plane of the Milky Way appear dark because...

stars in that region are hidden by dark dust particles.

The ________ of light passing through thin dust clouds lets us map the Galaxy's magnetic field.

polarization

Which of the following describes the shape of dust particles, based on polarization of light?

rodlike

The overall dimming of starlight by interstellar matter is called...

extinction.

Dust particles and magnetic fields in the interstellar medium are revealed by ________ of light.

polarization

The gas density in an emission nebula is typically about how many particles per cc?

hundred

What is the primary visible color of an emission nebula?

red (due to ionized hydrogen atoms)

A reflection nebula is caused by

starlight scattered by dust particles

Dark nebulae are opaque to all wavelengths of electromagnetic radiation. (T or F)

False

A dark cloud can be detected if it happens to block the light emitted by more distant stars. (T or F)

True

Interstellar dust clouds are best observed at what wavelength?

Radio and infrared

The average temperature of the typical dark dust cloud is about (k):

100 k

Why is 21-cm radiation so important to the study of interstellar matter and the Galaxy?
Emitted by carbon monoxide, it passes through interstellar gas and lets us to see places rich in organic molecules around the Galaxy.
It is emitted by most stars, enabling astronomers to map the entire Galaxy.
Emitted by hydrogen, it passes through interstellar dust and lets us to map the entire Galaxy.
It is emitted only in hot regions of star formation, so the pattern of the spiral arms of the Galaxy can be mapped.
It helps locate the galactic core in Sagittarius.

Emitted by hydrogen, it passes through interstellar dust and lets us to map the entire Galaxy.

When an electron in H changes its spin from the same to the opposite direction as the proton, it...

emits a radio wave photon.

The most common molecule in a molecular cloud is:

molecular hydrogen, H2

Most molecules found in the giant molecular clouds are based on silicon. (T or F)

False

The Local Bubble was probably created by:

a nearby supernova perhaps 300,000 years ago, brighter than the Full Moon.

Unlike atoms, molecules can:

vibrate and spin

What makes the subject of star formation so difficult and complex?

Stars live too long to be observed from birth to death

Our Sun, along with most of the stars in our neighborhood probably formed...

billions of years ago

What is the force that keeps a main sequence star from blowing apart?

gravitation

Rank these stages based on the order in which they occur, from first to last.
- molecular cloud fragment, protostar with jets, main sequence star, contracting cloud trapping infrared light

molecular cloud fragment, contracting cloud trapping infrared light, protostar with jets, main-sequence star

Rank these stages based on the central temperature, from highest to lowest.
molecular cloud fragment, protostar with jets, main sequence star, contracting cloud trapping infrared light

main sequence star, protostar with jets, contracting cloud trapping infrared light, molecular cloud fragment

Rank these stages based on their rotation rate, from fastest to slowest. (Assume that the angular momentum of the forming star is conserved throughout the formation process, though in fact it may shed some angular momentum by ejecting material into interstellar space.)
molecular cloud fragment, protostar with jets, main sequence star, contracting cloud trapping infrared light

main sequence star, protostar with jets, contracting cloud trapping infrared light, molecular cloud fragment

lasts about 10 billion years, energy generated by nuclear fusion, surface radiates energy a the same rate that core generates energy

main-sequence phase

pressure and gravity are not precisely balanced, radius much larger than the sun, luminosity much greater than the sun, energy generated by gravitational contraction

protostar phase

A star (no matter what its mass) spends most of its life:

as a main sequence star.

When a star's inward gravity and outward pressure are balanced, the star is said to be...

in hydrostatic equilibrium

What spectral type of star that is still around formed longest ago?

M

What spectral type of star that is still around formed most recently?

O

Which of the following elements contained in your body is NOT formed in the cores of stars during thermonuclear fusion?

hydrogen

The "helium flash" occurs at what stage in stellar evolution?

red giant

A solar mass star will evolve off the main sequence when...

it builds up a core of inert helium.

Life of a high-mass star. Rank the stages based on when they occur, from first to last.
- protostar, main-sequence O star, contracting cloud of gas and dust, neutron star, supernova, red supergiant

contracting cloud of gas and dust, protostar, main-sequence O star, red supergiant, supernova, neutron star

Provided following are various elements that can be produced during fusion in the core of a high mass main sequence star. Rank these elements based on when they are produced, from first to last.
- oxygen, carbon, iron, helium

helium, carbon, oxygen, iron

The following figures show various stages during the life of a star with the same mass as the Sun. Rank the stages based on when they occur, from first to last.
- main-sequence G star, planetary nebula, white dwarf, red giant, protostar, contracting cloud of gas and dust

contracting cloud of gas and dust, protostar, main-sequence G star, red giant, planetary nebula, white dwarf

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