Module 5 ASTR 100

How can we use density to estimate that the interior of the Earth must contain at least some iron?

In one approach, the mass of Earth can be found from the strength of Earth's gravity. Because meteorites and Earth formed at the same time out of similar materials, the overall composition of Earth should resemble the composition of meteorite material, which includes minerals with large amounts of iron.

What is the difference between spring and neap tides?

Spring tides are during Full and New moon and are the strongest tides created, while neap tides are on quarter moons and create the weakest tides.

Valles Marineris is: a) The largest canyon in the solar system. b) Formed from a crack as the crust of the planet cooled. c) Located on Mars. d) All of the above.

d) All of the above.

Which of the following statements is true? a) Small particles in an accretion disk will stick together because of static electricity. b) Clumps in the accretion disk that collided had to be moving very slowly relative to each other or else they would break into small pieces when they collided. c) Planetesimals get bigger because their gravity can pull in and capture other objects in the accretion disk. d) All of the above.

d) All of the above.

Which of these is true about our solar system? a) The objects in the asteroid belt did not combine to form a planet because of the gravity of Jupiter. b) The objects in the outermost part of the solar system did not combine to form a planet because of how far apart they were - collisions were not that common. c) A meteorite is a rock from space that survives to hit the Earth. d) All of the above.

d) All of the above.

Which of these is true about star formation? a) Within a molecular cloud, there are many dense cores - each can collapse to form a star or a star system. b) When a cloud core collapses, most of the material goes to the middle, forming a protostar. c) A protostar will collapse and get hotter inside - if it reaches 10 million degrees C, it can turn into a star. Heavier stars will form quicker than low mass stars. d) All of the above.

d) All of the above.

Which of these is true about the formation of our solar system? a) Our solar system formed when a molecular cloud collapsed. b) Our solar system formed approximately 4.5 billion years ago. c) Planets formed from a disk of gas and dust that surrounded the young Sun. d) All of the above.

d) All of the above.

Which of these statements is true? a) One way the interior of the Earth is kept warm is through radioactive decay. b) The two objects that create the strongest tides on the Earth are the Moon and Sun. c) Spring tides are much stronger tides (higher high tides and lower low tides) than neap tides. d) All of the above.

d) All of the above.

Which of these is part of our solar system? a) The Sun b) Trans-Neptunian Objects c) Planets c) Anything that orbits the Sun. d) Answer All of the above.

d) Answer All of the above.

Which of these objects on Earth formed in a way most similar to how Olympus Mons formed? a) Meteor Crater b) Grand Canyon c) Himalayan Mountains d) Hawaiian Islands

d) Hawaiian Islands

Which of these is NOT true about the interiors of the Earth and the other terrestrial planets? a) The very center of the Earth is a solid iron core. b) The outer parts of the terrestrial planets are rock and the center parts are iron. c) The liquid iron core of the Earth and Mercury help to produce magnetic fields. d) The magnet in a compass on the Earth will always point EXACTLY to Polaris.

d) The magnet in a compass on the Earth will always point EXACTLY to Polaris.

Which of these statements is true about the surface of the Earth? a) The continents have always been in the same places on the Earth. b) Volcanoes and earthquakes only occur in the middle of plates. c) Craters have never disappeared from the surface of the Earth. d) When two plates collide, mountains can form.

d) When two plates collide, mountains can form.

What is a blackbody? What happens to the color of a blackbody (like a protostar) as the temperature increases?

A blackbody is a source that absorbs and emits all the electromagnetic energy it receives, where spectrum/color depends on temperature. The color of a blackbody turns bluer the hotter it is in temperature.

What is a brown dwarf? How is the energy coming from a brown dwarf being made?

A brown dwarf is a protostar that never made it to the 10 million kelvin temperature to become a star, and sits at the space between a planet and a star. It's energy comes from thermal energy as it cools down over time.

What caused small particles in the accretion disk to stick together? Why did clumps stop growing as much when they reached 100 meters across?

A disk that forms from the coming together of (the accretion of) material around a massive object. The disc that's forming is held together by angular momentum. When clumps grow to about 100 meters across, the objects are so far apart that they collide less frequently, and their growth rate slows down but does not stop.

Why does a protostar shine? Hint: It's not because of nuclear fusion like a normal star.

A prostar gets to visibly shine once it reaches the temperature of 1000 kelvines. It shines through the temperature of the surface, not through it creating its own fusion energy.

When did most cratering occur in our solar system?

At the beginning when there was the most chaos happening. Craters are a good way to tell the general age of planets from afar.

What can cause a molecular cloud to collapse?

Collisions with other molecular clouds, space winds, gravitational interaction with other nearby stars, the explosion of a nearby star or the cloud can collapse under its own weight.

Why do clumps that collide in the accretion disk have to be very slow moving relative to each other?

For two large clumps to stick together rather than explode into many small pieces, they must bump into each other very gently; in fact, collision speeds must be about 0.1 meter per second (m/s) or less for colliding boulders to stick together.

What two terrestrial planets have decent-sized magnetic fields? What does this tell us about the interior of these planets?

Earth and Mercury. This tells us that these two planets have iron cores which help create the magnetic fields.

Why do Earth and Venus not have that many impact craters on the surface?

Earth's crater shortage is primarily due to plate tectonics in Earth's ocean basins and erosion on land, while lava flows on Venus have covered its craters.

What are two reasons why protostars are often not seen in visible light by astronomers?

First, most of the protostar's radiation is in the infrared rather than the visible part of the spectrum. Second, the protostar is buried deep in the heart of a dense and dusty molecular cloud and dust absorbs visible light

Why is Jupiter not considered a brown dwarf?

Jupiter is not considered a brown dwarf because it never got hot enough or large enough to even have the hope of being a star.

Why did the objects in the asteroid belt not combine to form a planet? Why did the outermost objects in the solar system not combine to form a planet?

Jupiter's gravity kept the region between Jupiter and Mars so stirred up that most planetesimals there could not merge to form a large planet.

What is the difference between a meteoroid, meteor, and meteorite?

Meteoroids are small (less than 100 meters) cometary or asteroid fragments in space. A meteoroid that enters and burns up in a planetary atmosphere is called a meteor. Any meteoroids that survive to hit the ground are known as meteorites.

Where are Kuiper Belt objects found? Where are most asteroids found?

More dwarf planets, along with a large number of smaller bodies, are found in the Kuiper Belt, beyond Pluto's orbit. Asteroids are small bodies found interior to Jupiter's orbit; most are located in the main asteroid belt between Mars and Jupiter.

What are two ways that the interior of the Earth is kept warm?

Radioactive heating. Some of the thermal energy in the interior of Earth is left over from when Earth formed. The tremendous energy of collisions and the energy from short-lived radioactive elements melted the plane. Tidal heating. If thermal energy were the only source of heating in Earth's interior, the outer core would have solidified completely. Given today's high internal temperatures, additional sources of energy must continue to heat the interior of Earth. One source of continued heating is friction from tidal effects of the Moon and Sun.

What is self-gravity? What are two ways that self-gravity can be balanced? Which one applies to the Earth and which one applies to an interstellar cloud?

Self gravity is a gravitational attraction among all parts of the same object. One way it can be balanced is through structural strength, like the rocks that make up the Earth. It can also be balanced by the outward force resulting from gas pressure, such as the pressure from hot gasses within a star. Structural strength applies to Earth while gas pressure applies to an interstellar cloud.

What is differentiation? Explain how it has helped the terrestrial planets get the interiors they have?

The Earth's interior is not uniform. The materials have been separated by density in a process known as differentiation. When solid rocks of different types are mixed together, they tend to stay mixed. Once this rock melts, however, the denser materials sink to the center and the less dense materials float toward the surface.

What happens to cause a protostar to turn into a star?

The core has to reach 10 million kelvin or above for the hydrogen to turn into helium and start being self-sufficient in its own energy through fusion.

What do the types of craters we see on Mars tell us about the surface of Mars when the craters formed?

The craters on mars look like they were made of rocks thrown into mud. At the time these craters formed, there may have been liquid water on the surface of Mars. Features resembling canyons and dry riverbeds are further evidence supporting this hypothesis. Another explanation for the appearance of these craters involves a change in surface temperature that might have occurred when the meteoroids hit, causing liquid water to exist temporarily.

What is the Earth's lithosphere?

The crust and part of the upper mantle form the lithosphere of a planet. Tectonism modifies the lithosphere—warping, twisting, and shifting it to form visible surface features

What are the dark spots that we find on the Moon? How did they form? How old are they?

The dark spots on the moon are known as maria, which is latin for "seas" because observers thought the dark spots looked like oceans. The maria are actually vast hardened lava flows, similar to volcanic rocks known as basalts on Earth. They are thought to be the youngest parts of the moon since they happened after the chaos in the beginning of the solar system.

What was the primary atmosphere of the planets? Why did that atmosphere not last long around small planets like the Earth?

The gas—primarily hydrogen and helium—that is captured by a planet at the time of its formation is the planet's primary atmosphere. The primary atmosphere of a large planet can be more massive than the solid body, as in the case of giant planets such as Jupiter. The primary atmosphere does not last long because of the volcanic activity putting carbon dioxide in the air as well as comets.

Why are mountains on Mars much larger than the mountains on the Earth?

The mountains on Mars are much larger than those on Earth because they were made from hot spot volcanoes. Mars also doesn't have tectonic plates, so the hot spot outpoured lava from the same place. Volcanoes on Mars have remained over their hot spots for billions of years, growing ever taller and broader with each successive eruption, eventually towering over the tallest of Earth's mountains.

Why are protostars often more luminous than our Sun?

The surface of a protostar is tens of thousands times larger than that of the sun. Due to its enormous size, it gives off more light than our sun does.

What two objects create the strongest tides on the Earth?

The two objects that create the strongest tides on Earth are when the Sun and Moon are lined up together on new and full moons to create spring tides.

Where do we typically find volcanoes on the Earth?

We typically find volcanoes on the edges of plates in plate tectonics, most frequently converging plates. Volcanoes are created when friction between plates melts rock, which is then pushed up through cracks to the surface. Earth also has numerous hot spots, such as the Hawaiian Islands, where hot deep-mantle material rises, releasing thermal energy. As plates shift, some parts move more rapidly than others, causing the plates to stretch, buckle, or fracture.

What are secondary craters? How are they formed?

When an object hits a planet, its energy heats and compresses the surface and throws material (labeled "ejected material" in the figure) far from the resulting impact crater. This material sometimes appears as rays—bright streaks pointing away from a young crater. Sometimes this material falls back to the surface of the planet with enough energy to cause more scars known as secondary craters

What is a planetesimal? How does a planetesimal get bigger?

When clumps of rock and debris that stick together grow to reach the size of about a kilometer, a different process becomes important. These kilometer-sized objects are massive enough that their gravity pulls strongly on nearby bodies, at which point they are known as planetesimals (literally "tiny planets"). At this point, the planetesimal is not growing only by chance collisions with other objects; now it can pull in and capture small objects outside its direct path.

The largest terrestrial planet is: a) Earth b) Jupiter c) Mars d) Mercury e) Venus

a) Earth

Which of these is NOT true about Olympus Mons? a) Olympus Mons is so large because of the very fast plate movements on Mars. b) Olympus Mons is taller than any mountain on the Earth. c) Olympus Mons is the tallest volcano on Mars d) Olympus Mons is a hot-spot volcano.

a) Olympus Mons is so large because of the very fast plate movements on Mars.

If you were living on Venus, you would notice that: a) Stars rise in the west and set in the east. b) Seasons are very similar to those on Earth but last twice as long. c) The Sun will appear to stop and move backwards in the sky for a little bit. d) All of the above.

a) Stars rise in the west and set in the east.

Which of these is NOT a reason more craters are on the Moon than on the Earth? a) The Moon blocks asteroids from hitting the Earth. b) The Moon has no atmosphere. c) The Moon has no oceans or water. d) The Moon has no erosion to wear down craters.

a) The Moon blocks asteroids from hitting the Earth.

Which of these is NOT a trigger that can cause a molecular cloud to collapse? a) Winds from young stars b) A black hole passes nearby c) Molecular clouds collide. d) A supernova explodes nearby.

b) A black hole passes nearby

Why does fusion never begin in a brown dwarf? a) Brown dwarfs are made of iron, which cannot fuse. b) Brown dwarfs do not get hot enough for fusion. c) Brown dwarfs are located so close to bright stars that fusion can't begin. d) Solar winds near brown dwarfs stop any fusion.

b) Brown dwarfs do not get hot enough for fusion.

What happens to a blackbody as its temperature increases? a) It looks redder. b) It puts out more light/energy. c) It gets smaller in size. d) All of the above.

b) It puts out more light/energy.

Which of these is true about the interiors of terrestrial planets? a) The centers of all the terrestrial planets are made of rock. b) The terrestrial planets would have rock and iron completely mixed together if they were not liquidy early on in their history. c) We have been able to use seismic waves to study the interiors of all the terrestrial planets. d) All of the above.

b) The terrestrial planets would have rock and iron completely mixed together if they were not liquidy early on in their history.

Which of these is true about the terrestrial planets? a) They are the four largest planets. b) They are the closest planets to the Sun. c) They orbit the Sun in the longest amount of time. d) They do not have a solid surface.

b) They are the closest planets to the Sun.

Which of these stars is the hottest? a) Red star b) Green star c) Blue star d) They are all the same temperature. e) It is impossible to tell.

c) Blue star

Molecular clouds look dark in the sky because: a) They contain a very large number of black holes. b) There are no stars located behind them. c) Gas and dust in the cloud blocks the light from getting through. d) All of the above.

c) Gas and dust in the cloud blocks the light from getting through.

Why do the maria have so few craters? a) The rock in the maria is so strong that craters aren't created when asteroids hit. b) The maria have many craters, but the maria are dark so we can't see the craters from Earth. c) The rock in the maria hardened after the time when most craters formed on the moon. d) The maria are oceans of water so asteroids that hit the maria do not form craters.

c) The rock in the maria hardened after the time when most craters formed on the moon.

According to the currently most accepted theory, the Moon: a) Formed at the same time as the Earth. b) Was captured by Earth's gravity as it flew by. c) Was formed after a large object hit the Earth. d) Does not exist.

c) Was formed after a large object hit the Earth.

Which of the following is true about craters? a) Craters can be very large because of how fast the impact object is traveling. b) Hellas Planitia is a very large crater on Mars. c) Most craters formed very early on in our solar system - within the 1st billion years. d) Smoother craters suggest that the surface was muddy or wet when it was hit. e) All of the above.

e) All of the above.