CH 1-5 :Astronomy

Flashcard maker : Ewan Tanner
Star
a large glowing ball of gas that generates head and light through nuclear fusion in its core. *sun is a star
planet
a large object that orbits a star and shines marily by reflecting light from its star.
Considered planet only if:
orbits a star, large enough to on gravity to make it round, has cleared most other objects from its orbital path.
Moon
an object that orbits a planet
asteroids
a relatively small and rocky object that orbits a star.
comets
a relatively small and one-rich object that orbits a star
Solar system
sun and all the material that orbits it
star system
a star sometimes more than one and any other planets and other materials that orbit it
galaxy
a great island of stars in space all held together by gravity and orbiting a common center
Cluster of galaxies
a collection of galaxies bound together by gravity.
supercluster
a gigantic region of space where many individual galaxies and many groups and clusters of galaxies are packed more closely together than elsewhere in the universe
universe
the sum total of all matter and energy- that is all galaxies and everything between them
observable universe
the portion of the entire universe that can be seen from Earth
AU
The average distance between Earth and the Sun, 150 million km
LY
the distance that light can travel in 1 year – 10 trillion km
rotation
the spinning of an object around its axis. Ex: Earth rotates once each dat around its axis
orbit
the orbital motion of one object around another. Ex: earth orbit around the sun once a year
Why can’t we see a galaxy 15 billion light-years away? (Assume the universe is 14 billion years old.)
Looking 15 billion light-years away means looking to a time before the universe existed
How did we come to be?
The matter in our bodies came from the Big Bang, which produced hydrogen and helium.
All other elements were constructed from H and He in stars and then recycled into new star systems, including our solar system.
How can we know what the universe was like in the past?
When we look to great distances, we are seeing events that happened long ago because light travels at a finite speed.
Can we see the entire universe?
No. The observable portion of the universe is about 14 billion light-years in radius because the universe is about 14 billion years old.
Let’s reduce the size of the solar system by a factor of 10 billion; the Sun is now the size of a large grapefruit (14 cm diameter).
a tip of a ballpoint pen
How big is the Earth compared to our solar system?
On a scale of 1-to-10 billion, the Sun is about the size of a grapefruit. The Earth is the size of a tip of a ballpoint pen about 15 m away. The distances between planets are huge compared to their sizes.
List our “Cosmic address” from large to small?
Earth, Solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe.
When we say the universe is expanding what do we mean
the average distance between galaxies is growing with time
If stars existed but galaxies did not,
we would not exist because we are made of material that was recycled in galaxies
Could we see a galaxy that is 20 billion light-years away?
No, because it would be beyond the sounds of our observable universe
The star betelgeuse is about 425 light-years away. If it explodes tonight,
we won’t know about it until 425 years later from now
If we represented the solar system on a scale that allowed us to walk from the Sun to Pluto in a few minutes, then
the planet would all be marl-size or smaller and the nearest stars would be a thousand of miles away
The total number of stars in the observable universe is roughly equivalent to
the number of grains of sand on all the beaches on earth
The age of our solar system is about
one-third of the universe
The fact that nearly all galaxies are moving away from the us, with more distant ones moving faster, tell us that
the universe is expanding
Two stars that are in the same constellation
may actually be very far away from each other
The north celestial pole is 35 degrees above your northern horizon. This tells you that
you are at latitude 35 degrees North
Beijing ans Philadelphia have about the same latitude but very different longitudes. Therefore, tonight’s night sky in these two places
will look about the same
In winter, Earth axis points toward the starPolaris. In spring,
the axis also points toward Polaris
When it is summer in Australia, the season in the United States is
Winter
If the sun rises precisely due east,
it must be the day of either the spring or fall equinox
A week after full moon, the phase is
a third quarter
Some type of lunar or solar eclipse occur
at least four times a year
When we see saturn going through a period of apparent retrograde motion, it means
Earth is passing Saturn in its orbit, with both planets on the same side of the sun
If there is going to be a total lunar eclipse tonight, then you know that
the Moon phase is full
In the Greek geocentric model, the retrograde motion of a planet occurs when
the planet actually goes backward in its orbit around Earth
Which is not a major advantage of Copernicus’s sun-centered model over the Ptolemaic model?
it made significantly better predictions of the planetary positions in our sky
When we say that a planet has a highly eccentric orbit, we mean that
in some parts of its orbit it is much closer to the sun than in other parts
Earth is closer to the sun in January then in July. Therefore, in accord with Kepler’s second law,
Earth travels faster in its orbits around the Sun in January than in July
According to Kepler’s 3rd law,
JUpiter orbits the sun at a faster speed then Saturn
Tycho Brahe’s contribution to astronomy included
collecting data that enabled Kepler to discover the laws of planetary motion
Galileo’s contribution to astronomy included
making observations and conducting experiments that dispelled scientific objections to the Sun-centered model
What is not true about scientific process?
science advances only through the scientific methods
What is not true about a scientific theory?
A theory is essentially an educated guess
Example that describes an object that is accelerating
a car going around a circular track at a steady 100 miles per hour
Suppose you visit another planet
your mass would be the same as on Earth, but your weight would be different
Which person is weightless?
a child in the air as she plays the trampoline
Consider that statement “there’s no gravity in space” this statement is
Completely false
to make a rocket turn left, you need to
fire an engine that shoots out gas to the right
compared to its angular momentum when it is farthest from the Sun, Earth’s angular momentum when it os nearest to the sun is
the same
the gravitational potential energy of a contracting interstellar cloud
gradually transforms into other forms of energy
If earth were twice as far from the Sun, the force of gravity attracting Earth to the Sun would be
one-quarter as strong
According to the law of universal graviton, what would happen to Earth if the SUn were somehow replaced by a black hole of the same mass?
Earths orbits would not change
If the Moon were closer to Earth, high tides would
be higher than they are now
Why is a sunflower yellow?
it reflects yellow light
Blue light has higher frequency than red light. Blue light therefore has
higher energy and shorter wavelength than red light
Radio waves are
a form of light
Compared to an atom as a whole an atomic nucleas
is very tiny but has most of the mass
some nitrogen atoms have 7 neutrons and some have 8 neutrons; these 2 forms of nitrogen are
isotopes of each other
the set of spectral lines that we see in a star’s spectrum depends on the star’s
atomic structure
a star whose spectrum peaks in the infrared is
cooler than our sun
a spectral line that appears at a wavelength of 328 nm in the spectrum of a distant object. We say that the objects spectrum is
Red Shifted
how much greater is the light-collecting area of a 6-meter telescope than that of a 3-meter telescope?
4 times
The Hubble space telescope obtains higher-resolution images than most ground-based telescope because it is
above Earths’ atmosphere

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