Konstantin Batygin, Phd '12, Assistant Professor of Plantetary Science and Van Nuys Page Scholar
AY/GE 133 Formation and Evolution of Planetary Systems
In December 2015, a new law titled “Low Volume Motor Vehicle Manufacturers Act” (H.R. 2675) was introduced in the U.S., which creates a reasonable regulatory structure allowing small companies to produce a limited number of completed replica motor vehicles that resemble the appearance of cars produced 25 years ago or more. Suppose that upon finding this out, you dish out all your savings (plus a loan from your parents) and buy a DeLorean. You set the destination time to - 4.5 Gyr, turn the flux capacitor on, and upon leaving the dealership parking lot, you accelerate to 88 miles an hour. After a brilliant flash of light, you find yourself submerged in the solar nebula (note that at t = - 4.5 Gyr, you predate the Earth by ~100 million years, since geochemical constraints place the moon-forming impact at ~60-100 million years after the formation of the sun), orbiting the Sun on a circular trajectory at 1 AU. [IMPORTANT: If you are reading this and thinking “huh?” then stop reading, rent “Back to the Future” and watch it].
For local disk parameters, reasonable values are: a surface density of ∑ ≈ 2000 g/cm2, an aspect ratio (vertical scale-height over orbital radius) of h/r ≈ 0.05, and a surface density profile that goes as ~1/r. Note further that the DeLorean is reminiscent of a primitive ~meter-sized planetesimal submerged within the nebula.
• What are your surroundings like?
• What are the temperatures of the dust and the gas outside?
• What is the nebula made of?
• Can you see the Sun?
• Does the nebular gas flow around your DeLorean like a fluid?
[Hint: How does the H2 mean free path compared to the size of the DeLorean.]
• How much headwind is the DeLorean feeling?
• How does this compare with the top speed of a 2010 Bugatti (type in “fastest car” into Google)? [Hint: The answer is not 88 miles per hour.]
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