JJJJ - Origin of the Solar System
We know that the giant planets (Jupiter, Saturn, Uranus and Neptune) initially formed very quickly because of the presence of water-ice in the outer solar system. This sticky material enabled planetesimals to form and grow quickly. Besides this reason, explain why the giant planets grew to such enormous sizes relative to the smaller, terrestrial worlds (Mercury, Venus, Earth and Mars).
--
In the outer solar system, one of the reasons the giant planets (the Jovians) all became so large is because they got a bit of a “jump start” in the initial stages of formation.
a) Describe what happened in the initial stages of formation (before they started collecting gas such as Hydrogen and Helium) that made these planets form so quickly.
b) Why did this only happen with the giant planets (Jupiter, Saturn, Uranus and Neptune) and not the terrestrials (Mercury, Venus, Earth and Mars)?
--
All four of the terrestrial planets (Mercury, Venus, Earth and Mars) have significant cores of iron. Taking Earth/Venus as an example, explain why the iron in the Earth/Venus is concentrated mostly in the core instead of being evenly distributed throughout the entire Earth/Venus?
--
What is the primary process in the formation of Uranus and Neptune that led to their smaller size relative to the other two gas giants, Jupiter and Saturn?
--
The Earth is the only one of the four terrestrial planets (Mercury, Venus, Earth and Mars) to have a significant amount of water.
a) (3 pts) How do we know that the source of Earth’s water is likely from impacts with comets early in the history of the solar system?
b) (3 pts) Any argument given in (a) must also be true for Mars. What, then, is the primary reason why Mars has no significant water on its surface?
--
The solar nebula, prior to its collapse, was a spherical cloud with a little rotation. What part did this rotation play in causing the disk to flatten out as it collapsed? You may want to draw a diagram to help explain your answer (diagram alone is not sufficient).
--
One theory to explain the origin of the solar system says that after the Sun formed, a passing star came close enough to the Sun that tidal forces ripped off the Sun’s outer layers into a disk of gas and dust that eventually condensed to form an orbiting group of planets. Name and explain (1-2 sentences each) two pieces of evidence that argue against this theory.
--
About 10-15 years ago, scientists set out to use the latest infrared technology to search for disks of gas and dust around nearby Sun-like stars. They expected to find such disks around many such stars. Explain why they expected this, in 2-3 sentences (note that I am not asking how they did it).
--
Over the past 10 years, using Doppler shift techniques, scientists have discovered several systems in which a planet with a mass greater than or equal to the mass of Jupiter has been found orbiting its parent star at a distance of about 0.4 Astronomical Units (close to Mercury’s orbital distance from the Sun). Name and explain two reasons why such systems serve as counterexamples that argue against our theory of how the giant planets in our solar system formed.
--
The presence of deuterium in the atmospheres of various planets is considered to be evidence against the idea that the solar nebula was formed by material stripped from the Sun after the Sun formed, thanks to the influence of a passing star. Explain why the presence of deuterium in the solar system today argues against this so-called “catastrophe” theory of solar system formation.
--
Jupiter’s composition can be explained by the theory of the origin of the solar system.
a) (6 pts) Does Jupiter have any rock or metal in its interior? Explain.
b) (6 pts) Besides escape velocity, explain at least one reason that Jupiter managed to capture Hydrogen and Helium gas to form much of its composition while Earth did not.
--
We know that the Earth’s Moon has an isotope fingerprint that is identical to that of the Earth, yet it lacks volatiles, unlike the Earth. The Moon also seems to lack a dense iron core, unlike the Earth, so the overall density of the Moon is lower than that of the Earth.
a) (3 pts) Briefly explain what a volatile element is.
b) (5 pts) What does the lack of volatiles on Earth’s Moon imply about its formation conditions?
--
One theory to explain the origin of the solar system says that after the Sun formed, a passing star came close enough to the Sun that tidal forces ripped off the Sun’s outer layers into a disk of gas and dust that eventually condensed to form an orbiting group of planets. Name and explain (1-2 sentences each) two pieces of evidence that argue against this theory.
--
One model of the origin of the solar system asserts that the planet Mercury (with an almost purely metallic composition) formed at a relatively large distance from the Sun (further away from the Sun that the Earth was when Earth formed). According to this model, Mercury subsequently interacted with the other planets and moved to its current orbital distance today. How does Mercury’s composition argue against this model? Explain in 2-3 sentences (only saying “the model is wrong because Mercury’s composition is mostly metallic” just repeats the information given and will result in no credit).
--
Upstairs in the lobby of the Sid W. Richardson building, you can find several extremely dense and massive meteorites made of pure iron. How do we know that these meteorites are almost certainly pieces broken off a much larger asteroid? Explain.
--
When the original giant interstellar gas and dust cloud collapsed to form the solar nebula (from which the planets would later condense), it heated up in the center and collapsed into a disk shape.
a) (6 pts) State in 1-2 sentences why the solar nebula heated up.
b) (8 pts) Explain (with the help of a simple diagram...a diagram itself is not sufficient) why the solar nebula collapsed into a disk shape.
--
Early on during the formation of the solar system, the inner portion of the solar nebula disk was much hotter (in the region where Mercury would eventually form) relative to the portion further away (in the region where Earth would eventually form).
a) (7 pts) State briefly how the composition of the Earth differs from that of Mercury. Explain why this temperature difference may have led to Mercury's composition being much different from that of the Earth.
b) (7 pts) Today, Mercury's location in the solar system gets much more energy from the Sun (according to the inverse square law) compared to the Earth. Explain why this fact makes it much less likely for Mercury to retain an atmosphere.
--
One hypothesis that has been suggested to explain the origin of our solar system is known as the "capture" hypothesis (be careful here and don't get the capture hypothesis and the catastrophe hypothesis mixed up). The observation that planetary orbits are all roughly coplanar is often cited by Astronomers as a reason to doubt the capture hypothesis.
a) (7 pts) In a sentence or two, briefly summarize the capture hypothesis. Then explain why the coplanar nature of planetary orbits is used to argue against this hypothesis.
b) (7 pts) Explain how Astronomers believe the coplanar orbits of the planets came about in the more commonly accepted solar nebula model. In other words, why does the nebular model predict coplanar orbits instead of randomly mixed orbits? What gave the solar system its flattened shape?
--
Two possible theories regarding the origin of the solar system are the capture hypothesis and the catastrophe hypothesis. In 1-2 sentences each, explain one piece of evidence for each theory which have caused Astronomers to believe that the theory is incorrect.
--
Tidal interactions can be used to explain several phenomena in planetary astronomy, including things outside our own solar system.
a) (6 pts) Tidal forces are currently pulling Neptune’s moon Triton inward, and this fact is related to Triton’s origin. Explain how we know that Neptune’s moon Triton is a captured satellite rather than one that formed as part of the Neptune system originally.
b) (8 pts) When large planets form in other solar systems, some models suggest that they spiral inward toward their parent star due to a kind of frictional force with the dusty disk they formed from. Explain two reasons (one of them having to do with tidal forces) why in these models the planets stop spiraling inward and are left at very close distances to their parent stars (which would explain dozens of the systems seen so far that look like this).
--
In our solar system, the densities of planets generally decrease as one looks further from the Sun.
a) (4 pts) Explain this trend by talking about the origin of our solar system.
b) (4 pts) The size of planets also generally increases as one looks further from the Sun. Explain two reasons why Jupiter is so much larger than the Earth.
--
Many astronomers believe that our solar system formed from a spherical nebula, the collapse of which was triggered by a nearby supernova. What evidence related to atomic isotopes led Astronomers to believe the solar nebula collapse was triggered by a supernova?
--
One reason Jupiter grew to be such a large size relative to the terrestrial planets is that it has an extremely large feeding zone.
a) (8 pts) Name and briefly explain two other reasons Jupiter grew to be such an enormous mass (320 times the mass of Earth).
b) (6 pts) Neptune had a feeding zone about 60 times larger than that of Jupiter, yet it grew to a much lower mass. Explain why.