Exam 1 Flashcards
Write 23,500 in scientific notation:
2.35 x 10^4
Write the number that corresponds to the following scientific notation 3 x 10^-3
0.003
Knowing that y=32, what is the value of x?
Y = 3x
X = 10.67
Knowing that y=32 and c=345, what is the value of x?
X=0.093
Knowing that x=20, what is the value of y?
Y=3x^3
Y=24,000
Study of the objects that lie beyond our planet and the processes by which these objects interact with one another
Astronomy
Science that studies the physical laws involved in the processes of formation and evolution of everything in the universe
Astrophysics
79,200,000,000 in scientific notation is written as:
7.92 x 10^10
Is a unit of distance
Light year (lay)
Why do we say light year?
Because we know the speed of light, so, knowing how many years it takes the light to go from one point to another we know how much space it traveled
How long does it take for the moon to revolve around the earth?
1 month (28 days)
How many times have you gone around the sun?
About ~ my age
What is a star?
Gigantic ball of gas that generates enormous amounts of energy by nuclear reactions that happen inside them
Is a disk galaxy, with a bar and a small bulge
The Milky Way
How far is the Milky Way?
100,000 light-years
Material in-between stars
Interstellar material
Blocks the visible light of more distant stars, luckily it doesn’t block their light in the infrared!
Dust is a light eater
Matter that we cannot see
Dark matter
Do stars live alone or in groups?
Some stars live alone: like the sun
Regions where many stars were born together and contain hundreds of thousands of stars and take up volumes of space hundreds of light-years across
Star clusters
Are star clusters A) larger or B) smaller than our galaxy?
Smaller
Going further out what can we find?
- Isolated (on their own)
- In groups (with a few other galaxies)
- In clusters (with thousands of galaxies)
- In super clusters (these contains clusters, groups, and galaxies in isolation)
Are all the galaxies discovered already?
Not even close!
What are quasars?
- Extremely bright centers of galaxies
- Brightness is generated by gas that gets heated as it falls into the black hole at the center of the galaxy and swirls around it
- We see quasars as far as 10 or more billion light-years, which is looking 10 billion years in the past
What’s the closet galaxy to the Milky Way (that is not a satellite)?
Andromeda
What are dwarf galaxies?
Galaxies less massive than our own galaxy
How does everything look from our perspective?
- Everything moves around us
- But earth is not at the center of anything!
- Stars, as the sun, and moon, rise from the east and set on the west
- It seems that the sky is a spere that turns around us
What is the celestial sphere?
- But, it is not the sky that turns, but us that move!
- Because the earth turns on it axis every 24h, we see celestial objects rise and set
Stars that never rise or set
Circumpolar stars
Is there a place on earth where you can theoretically see all the stars in the sky?
Yes, from the equator
Do stars move during day time?
Yes
Path the sun appears to take around the celestial sphere each year
Ecliptic
What else is in the same plane of the sun?
Anything on that plane will move on the ecliptic
Why does the height of the north celestial pole vary from one image to the next?
Latitude of site has changed
What are constellations useful for?
- Navigation
- Calendar
- Naming locations in the sky
- Mythology
1 actual earth rotation relative to distant (“fixed”) stars
Sidereal day
1 earth rotation relative to sun (noon to noon)
Solar day
Which is longer: solar or sidereal day?
Solar
Which day is on our clocks, calendars?
Solar = 24hrs
Path of an object through space
Orbits
The orbits of all planets are ellipses and the sun is at one focus of the ellipse
First law
The straight line joining a planet and the sun sweeps out equal areas in space in equal intervals of time
Second law
The orbital period of planet squared is equal to the semimajor axis of its orbit cubed (if the period is in years and the semimajor axis is in astronomical units)
Third law
Is time the planet takes to travel once around the sun
Orbital period P
Average distance from the sun
Semimajor axis a
Can planets have circular orbits according to Kepler’s law?
Yes, the circle is a special case of an ellipse, that with ellipticity = 0
An asteroid with an orbital period of 8 years lies at an average distance from the sun equal to
4 astronomical units
Rate at which object moves
Speed
Speed and direction
Velocity
Any change in velocity unites of speed/time (m/s^2)
Acceleration
Every object will continue to be in a state of rest or move at a constant speed in a straight line unless it is compelled to change by an outside force
Newton’s First Law
The change of motion of a body is proportional to and in the direction of the force acting on it
Newton’s Second Law
Mass X Acceleration
Force
For every force, there is always and equal and opposite force
Newton’s third law
Amount of matter in an object
Mass
Force that acts upon an object due to gravity
Weight
On the Moon my weight…
Is less, my mass is the same
How does the force the earth exerts on you compare with the force you exert on it?
Earth and you exert equal and opposite forces on each other
On Mars, if two bricks with the same geometry are released from a tower, one with 2 pounds and one with .05 pounds, the 2 pound brick hits the ground first
False, they will reach the ground together
Describe the motion in a straight line
Newton’s laws of motion
Kepler found that planets move in ellipses, what’s bending their path?
Gravity
Newton’s universal law of gravitation…
- Every mass attracts every other mass
- Attraction is directly proportional to the product of their masses
- Attraction is inversely proportional to the square of the distance between their centers
Is any circle on the surface of a sphere whose center intersects the center of the sphere
Great circle
Is the number of degrees of arc you are away from the equator along your meridian
Latitude
Is the equivalent of longitude and declination is the equivalent of latitude
Right-ascension
The point where the ecliptic crosses the celestial equator
Equinox
How does the sun favoring one of the hemisphere translate into more or less warmth?
- If a hemisphere “leans” towards the sun the light rays hit on a more straight angle and “diffuse” the light less
- The length of time the sun spends above the horizon
The equator defines the zero-th degree of
Latitude (N-S)
The Sun’s altitude on the sky depend on?
Latitude of the place + time of the year
In the north hemisphere, days are shorter in winter and longer in summer. In the southern hemisphere?
Same than in the north: days are longer in summer but shorter in winter
Occurs whenever any part of either earth or the moon enter the shadow of the other
Eclipse
If an eclipse of the sun occurs when the moon is somewhat nearer than its average distance, the moon can completely hid the sun
Total solar eclipse
The moon phases
Are the same from every point on earth
A solar eclipse occurs when
The moon blocks sunlight from reaching the earth
Occurs when the moon enters the shadow of the earth
Lunar eclipse
How big is earth’s dark shadow?
1.4 million kilometers long
Who can see the lunar eclipse?
Is visible to everyone who can see the moon
What is beyond Neptune?
- The orbit of the 8 plants are more or less well aligned into a single place, providing clues to the origin of the solar system
- celestial bodies like these dwarf planets are referred to as “trans neptunian objects” (TNOs)
Mass/volume
Density
How do we determine masses?
From their gravitational effects on nearby objects
What are the three major goals of the Apollo missions?
- The astronauts collected nearly 400 kg of samples (~ 882 pounds) for detailed laboratory analysis on Earth. These samples have revealed as much about the Moon and its history as all other lunar studies combined.
- Each Apollo landing after the first one deployed an Apollo Lunar Surface Experiment Package (ALSEP), which continued to operate for years after the astronauts departed.
- The orbiting Apollo command modules carried a wide range of instruments to photograph and analyze the lunar surface from above.
How long ago was the earth and moon formed?
4.5 and 4.6 billion years ago
Involved the release of lava from hundreds of kilometers below the surface, ended about 3.3 billion years abgo
The major mare volcanism
What is the cratering process?
- The impact occurs
- The projectile vaporizes and a shock wave spreads through the lunar rock
- Ejecta are thrown out of the crater
- Most of the ejected material falls back to fill the crater, but some of it is found outside the crater in the form of an ejecta blanket
The Moon’s chemical composition is:
Very different from Earth because is high in light silicates and is missing most heavy metals
The origin of most craters on the Moon is:
External impacts, as solar system bodies crashed on the Moon
The Moon was formed:
Approximately at a similar time than Earth, 4.5-4.6 billion years ago
How is the surface in Venus like?
- We cannot see the surface, but imagining radar maps gives us information on the geology of Venus
- Similar appearance to earth in terms of elevations or valleys, but no evidence of tectonic plates
How is the temperature in Venus?
Very hot! ~700 K
How does the “daylight” look in Venus:
It is similar to Earth in terms of landscape, but it is quite dark even during daytime because of the atmosphere
Mars suffers of intense dust storm, with continent-sized dusty patches that can be detected even from telescopes on Earth. Once every ~5 years a dust storm may grow enough to engulf the whole planet. What does this means for possible future missions with astronauts:
It will get uncomfortable, but the thins atmosphere on Mars prevent these storms from making real damage
What are some challenges of space exploration for giant planets?
- Flight times are measured in years to decades (compound to months for Venus or mars)
- Messages take hours to pass between earth and the spacecraft. Need machines with great independice and autonomy
- Outer solar system missions must carry their own power source (Sun is far)
- Heaters are required to keep instruments at proper operating temperatures
- Spacecraft must have powerful radio transmitters to send their data to receivers on earth
How is Jupiter?
- ~5 AU from the sun
- 1 year = 12 earth years
- 320x mass of earth
- No solid surface
- Made mostly of H and He
- Bands and “swirls” caused by large weather patterns
- At least 60 moons!!
What are the bands on Jupiter?
The bands on Jupiter move at different speeds
How is Saturn?
- ~9.5 AU from the sun
- 1 year = 29 earth years
- 95x mass of earth
- No solid surface
- Made mostly of H and He
- Bands ands “swirls” caused by large weather patterns
- 31 moons
Giant planets are:
More massive and more extended than the terrestrial planets
The colorful bands on the giant planets are a consequence of:
Weather patters moving at different speeds and interacting with one another
How do the length of the years (1 revolution around the sun) compare:
Earth < Jupiter < Saturn
When was Uranus discovered?
1781
Are created as tiny solid particles that enter Earth’s atmosphere from interplanetary space
Meteors
Because meteros move fast, the friction with the atmosphere vaporizes them with a flash of light is called
Shooting Stars
Meteors that strike Earth
Comets
When Earth’s intersects that “cloud” we experience a
Meteor Shower
Any fragment of interplanetary debris that survives evaporation on Earth’s atmosphere
Meteorites
What is the formation of terrestrial planets?
All solid material condensates into planetsimals, which then are accreted onto each other to form more massive bodies (planets)
What is the formation of gas giants?
- Collapsed masses can be larger in the outer regions where there is gas and ices in addition to rocks.
- Planetesimals get massive enough to retain all the hydrogen gas around them.
- They also heat up a lot in the process! (But not enough to ignite nuclear reactions like the stars)
The conservation of angular momentum in the early stages of the solar system helps explain:
That all planet’s orbits are approximately on the same plane
Where is the asteroid belt located?
Between Mars and Jupiter and the Kuiper Belt
Enormous ball of extremely hot, largely ionized gas, shinning under its own power
The Sun
What does ionized mean?
- Many atoms have been stripped from one or more electrons
- This produces a ‘soup’ of free electrons and positively charged ions
Electrically charged soup
Plasma
What information do we get from the H-R diagram?
- Luminosity
- Temperature (special type)
- Size (radius)
- Mass (only MS stars!) (ms = main sequence)
What are the special properties of the main sequence (MS)?
- Stars in the MS are fusing 4 protons into 1 Helium nucleus
- Stars spend 90% of their lives during H (protons) into He
- Stars spend 90% of their lives in the MS
- Most of the stars, ~90%, are in the MS
Why are they more luminous?
- More massive means stronger gravity.
- More gravity compresses more their centers.
- More compressed cores means hotter temperatures.
- High temperature implies higher efficiency fusing protons (H) into He.
- More fusion reactions means more energy.
- More energy means more luminosity.
- More luminous because they are more massive!
Where are stars formed?
Formed in regions of massive reservoirs of gas and dust
What are the reservoirs that stars are formed in?
Molecular clouds
Have molecules in them, so they have cool temperatures
Molecular clouds
What is the process of star formation?
- Dense cores are formed inside the molecular clouds because of gravity overcoming pressure
- These dense cores rapidly collapse due to gravity and the density increases even more
- A protostar is born
Once the protostar is born, what’s next?
- The protostar already has a mass (M), a luminosity (L), and a temperature (T).
- It’s different from a star because it isn’t transforming H into He just yet (the temperature is not high enough in the core).
- Because it’s an object with M, L, and T, we can place it in an
- “H-R diagram of protostars”. (We call this kind of diagram ‘evolutionary tracks’.)
